[tig] / tig.c

/* Copyright (c) 2006 Jonas Fonseca <fonseca@diku.dk>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */
/**
 * TIG(1)
 * ======
 *
 * NAME
 * ----
 * tig - text-mode interface for git
 *
 * SYNOPSIS
 * --------
 * [verse]
 * tig [options]
 * tig [options] [--] [git log options]
 * tig [options] log  [git log options]
 * tig [options] diff [git diff options]
 * tig [options] show [git show options]
 * tig [options] <    [git command output]
 *
 * DESCRIPTION
 * -----------
 * Browse changes in a git repository. Additionally, tig(1) can also act
 * as a pager for output of various git commands.
 *
 * When browsing repositories, tig(1) uses the underlying git commands
 * to present the user with various views, such as summarized commit log
 * and showing the commit with the log message, diffstat, and the diff.
 *
 * Using tig(1) as a pager, it will display input from stdin and try
 * to colorize it.
 **/

#ifndef VERSION
#define VERSION "tig-0.3"
#endif

#ifndef DEBUG
#define NDEBUG
#endif

#include <assert.h>
#include <errno.h>
#include <ctype.h>
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <time.h>

#include <curses.h>

static void die(const char *err, ...);
static void report(const char *msg, ...);
static void set_nonblocking_input(bool loading);
static size_t utf8_length(const char *string, size_t max_width, int *coloffset, int *trimmed);

#define ABS(x)          ((x) >= 0  ? (x) : -(x))
#define MIN(x, y)       ((x) < (y) ? (x) :  (y))

#define ARRAY_SIZE(x)   (sizeof(x) / sizeof(x[0]))
#define STRING_SIZE(x)  (sizeof(x) - 1)

#define SIZEOF_REF      256     /* Size of symbolic or SHA1 ID. */
#define SIZEOF_CMD      1024    /* Size of command buffer. */

/* This color name can be used to refer to the default term colors. */
#define COLOR_DEFAULT   (-1)

#define TIG_HELP        "(d)iff, (l)og, (m)ain, (q)uit, (h)elp"

/* The format and size of the date column in the main view. */
#define DATE_FORMAT     "%Y-%m-%d %H:%M"
#define DATE_COLS       STRING_SIZE("2006-04-29 14:21 ")

#define AUTHOR_COLS     20

/* The default interval between line numbers. */
#define NUMBER_INTERVAL 1

#define TABSIZE         8

#define SCALE_SPLIT_VIEW(height)        ((height) * 2 / 3)

/* Some ascii-shorthands fitted into the ncurses namespace. */
#define KEY_TAB         '\t'
#define KEY_RETURN      '\r'
#define KEY_ESC         27


/* User action requests. */
enum request {
        /* Offset all requests to avoid conflicts with ncurses getch values. */
        REQ_OFFSET = KEY_MAX + 1,

        /* XXX: Keep the view request first and in sync with views[]. */
        REQ_VIEW_MAIN,
        REQ_VIEW_DIFF,
        REQ_VIEW_LOG,
        REQ_VIEW_HELP,
        REQ_VIEW_PAGER,

        REQ_ENTER,
        REQ_QUIT,
        REQ_PROMPT,
        REQ_SCREEN_REDRAW,
        REQ_SCREEN_RESIZE,
        REQ_SCREEN_UPDATE,
        REQ_SHOW_VERSION,
        REQ_STOP_LOADING,
        REQ_TOGGLE_LINE_NUMBERS,
        REQ_VIEW_NEXT,
        REQ_VIEW_CLOSE,
        REQ_NEXT,
        REQ_PREVIOUS,

        REQ_MOVE_UP,
        REQ_MOVE_DOWN,
        REQ_MOVE_PAGE_UP,
        REQ_MOVE_PAGE_DOWN,
        REQ_MOVE_FIRST_LINE,
        REQ_MOVE_LAST_LINE,

        REQ_SCROLL_LINE_UP,
        REQ_SCROLL_LINE_DOWN,
        REQ_SCROLL_PAGE_UP,
        REQ_SCROLL_PAGE_DOWN,
};

struct ref {
        char *name;             /* Ref name; tag or head names are shortened. */
        char id[41];            /* Commit SHA1 ID */
        unsigned int tag:1;     /* Is it a tag? */
        unsigned int next:1;    /* For ref lists: are there more refs? */
};

static struct ref **get_refs(char *id);


/*
 * String helpers
 */

static inline void
string_ncopy(char *dst, const char *src, int dstlen)
{
        strncpy(dst, src, dstlen - 1);
        dst[dstlen - 1] = 0;

}

/* Shorthand for safely copying into a fixed buffer. */
#define string_copy(dst, src) \
        string_ncopy(dst, src, sizeof(dst))


/* Shell quoting
 *
 * NOTE: The following is a slightly modified copy of the git project's shell
 * quoting routines found in the quote.c file.
 *
 * Help to copy the thing properly quoted for the shell safety.  any single
 * quote is replaced with '\'', any exclamation point is replaced with '\!',
 * and the whole thing is enclosed in a
 *
 * E.g.
 *  original     sq_quote     result
 *  name     ==> name      ==> 'name'
 *  a b      ==> a b       ==> 'a b'
 *  a'b      ==> a'\''b    ==> 'a'\''b'
 *  a!b      ==> a'\!'b    ==> 'a'\!'b'
 */

static size_t
sq_quote(char buf[SIZEOF_CMD], size_t bufsize, const char *src)
{
        char c;

#define BUFPUT(x) do { if (bufsize < SIZEOF_CMD) buf[bufsize++] = (x); } while (0)

        BUFPUT('\'');
        while ((c = *src++)) {
                if (c == '\'' || c == '!') {
                        BUFPUT('\'');
                        BUFPUT('\\');
                        BUFPUT(c);
                        BUFPUT('\'');
                } else {
                        BUFPUT(c);
                }
        }
        BUFPUT('\'');

        return bufsize;
}


/**
 * OPTIONS
 * -------
 **/

static const char usage[] =
VERSION " (" __DATE__ ")\n"
"\n"
"Usage: tig [options]\n"
"   or: tig [options] [--] [git log options]\n"
"   or: tig [options] log  [git log options]\n"
"   or: tig [options] diff [git diff options]\n"
"   or: tig [options] show [git show options]\n"
"   or: tig [options] <    [git command output]\n"
"\n"
"Options:\n"
"  -l                          Start up in log view\n"
"  -d                          Start up in diff view\n"
"  -n[I], --line-number[=I]    Show line numbers with given interval\n"
"  -t[N], --tab-size[=N]       Set number of spaces for tab expansion\n"
"  --                          Mark end of tig options\n"
"  -v, --version               Show version and exit\n"
"  -h, --help                  Show help message and exit\n";

/* Option and state variables. */
static bool opt_line_number     = FALSE;
static int opt_num_interval     = NUMBER_INTERVAL;
static int opt_tab_size         = TABSIZE;
static enum request opt_request = REQ_VIEW_MAIN;
static char opt_cmd[SIZEOF_CMD] = "";
static char opt_encoding[20]    = "UTF-8";
static FILE *opt_pipe           = NULL;

/* Returns the index of log or diff command or -1 to exit. */
static bool
parse_options(int argc, char *argv[])
{
        int i;

        for (i = 1; i < argc; i++) {
                char *opt = argv[i];

                /**
                 * -l::
                 *      Start up in log view using the internal log command.
                 **/
                if (!strcmp(opt, "-l")) {
                        opt_request = REQ_VIEW_LOG;
                        continue;
                }

                /**
                 * -d::
                 *      Start up in diff view using the internal diff command.
                 **/
                if (!strcmp(opt, "-d")) {
                        opt_request = REQ_VIEW_DIFF;
                        continue;
                }

                /**
                 * -n[INTERVAL], --line-number[=INTERVAL]::
                 *      Prefix line numbers in log and diff view.
                 *      Optionally, with interval different than each line.
                 **/
                if (!strncmp(opt, "-n", 2) ||
                    !strncmp(opt, "--line-number", 13)) {
                        char *num = opt;

                        if (opt[1] == 'n') {
                                num = opt + 2;

                        } else if (opt[STRING_SIZE("--line-number")] == '=') {
                                num = opt + STRING_SIZE("--line-number=");
                        }

                        if (isdigit(*num))
                                opt_num_interval = atoi(num);

                        opt_line_number = TRUE;
                        continue;
                }

                /**
                 * -t[NSPACES], --tab-size[=NSPACES]::
                 *      Set the number of spaces tabs should be expanded to.
                 **/
                if (!strncmp(opt, "-t", 2) ||
                    !strncmp(opt, "--tab-size", 10)) {
                        char *num = opt;

                        if (opt[1] == 't') {
                                num = opt + 2;

                        } else if (opt[STRING_SIZE("--tab-size")] == '=') {
                                num = opt + STRING_SIZE("--tab-size=");
                        }

                        if (isdigit(*num))
                                opt_tab_size = MIN(atoi(num), TABSIZE);
                        continue;
                }

                /**
                 * -v, --version::
                 *      Show version and exit.
                 **/
                if (!strcmp(opt, "-v") ||
                    !strcmp(opt, "--version")) {
                        printf("tig version %s\n", VERSION);
                        return FALSE;
                }

                /**
                 * -h, --help::
                 *      Show help message and exit.
                 **/
                if (!strcmp(opt, "-h") ||
                    !strcmp(opt, "--help")) {
                        printf(usage);
                        return FALSE;
                }

                /**
                 * \--::
                 *      End of tig(1) options. Useful when specifying command
                 *      options for the main view. Example:
                 *
                 *              $ tig -- --since=1.month
                 **/
                if (!strcmp(opt, "--")) {
                        i++;
                        break;
                }

                /**
                 * log [git log options]::
                 *      Open log view using the given git log options.
                 *
                 * diff [git diff options]::
                 *      Open diff view using the given git diff options.
                 *
                 * show [git show options]::
                 *      Open diff view using the given git show options.
                 **/
                if (!strcmp(opt, "log") ||
                    !strcmp(opt, "diff") ||
                    !strcmp(opt, "show")) {
                        opt_request = opt[0] == 'l'
                                    ? REQ_VIEW_LOG : REQ_VIEW_DIFF;
                        break;
                }

                /**
                 * [git log options]::
                 *      tig(1) will stop the option parsing when the first
                 *      command line parameter not starting with "-" is
                 *      encountered. All options including this one will be
                 *      passed to git log when loading the main view.
                 *      This makes it possible to say:
                 *
                 *      $ tig tag-1.0..HEAD
                 **/
                if (opt[0] && opt[0] != '-')
                        break;

                die("unknown command '%s'", opt);
        }

        if (!isatty(STDIN_FILENO)) {
                /**
                 * Pager mode
                 * ~~~~~~~~~~
                 * If stdin is a pipe, any log or diff options will be ignored and the
                 * pager view will be opened loading data from stdin. The pager mode
                 * can be used for colorizing output from various git commands.
                 *
                 * Example on how to colorize the output of git-show(1):
                 *
                 *      $ git show | tig
                 **/
                opt_request = REQ_VIEW_PAGER;
                opt_pipe = stdin;

        } else if (i < argc) {
                size_t buf_size;

                /**
                 * Git command options
                 * ~~~~~~~~~~~~~~~~~~~
                 * All git command options specified on the command line will
                 * be passed to the given command and all will be shell quoted
                 * before they are passed to the shell.
                 *
                 * NOTE: If you specify options for the main view, you should
                 * not use the `--pretty` option as this option will be set
                 * automatically to the format expected by the main view.
                 *
                 * Example on how to open the log view and show both author and
                 * committer information:
                 *
                 *      $ tig log --pretty=fuller
                 *
                 * See the <<refspec, "Specifying revisions">> section below
                 * for an introduction to revision options supported by the git
                 * commands. For details on specific git command options, refer
                 * to the man page of the command in question.
                 **/

                if (opt_request == REQ_VIEW_MAIN)
                        /* XXX: This is vulnerable to the user overriding
                         * options required for the main view parser. */
                        string_copy(opt_cmd, "git log --stat --pretty=raw");
                else
                        string_copy(opt_cmd, "git");
                buf_size = strlen(opt_cmd);

                while (buf_size < sizeof(opt_cmd) && i < argc) {
                        opt_cmd[buf_size++] = ' ';
                        buf_size = sq_quote(opt_cmd, buf_size, argv[i++]);
                }

                if (buf_size >= sizeof(opt_cmd))
                        die("command too long");

                opt_cmd[buf_size] = 0;

        }

        return TRUE;
}


/**
 * ENVIRONMENT VARIABLES
 * ---------------------
 * Several options related to the interface with git can be configured
 * via environment options.
 *
 * Repository references
 * ~~~~~~~~~~~~~~~~~~~~~
 * Commits that are referenced by tags and branch heads will be marked
 * by the reference name surrounded by '[' and ']':
 *
 *      2006-03-26 19:42 Petr Baudis         | [cogito-0.17.1] Cogito 0.17.1
 *
 * If you want to filter out certain directories under `.git/refs/`, say
 * `tmp` you can do it by setting the following variable:
 *
 *      $ TIG_LS_REMOTE="git ls-remote . | sed /\/tmp\//d" tig
 *
 * Or set the variable permanently in your environment.
 *
 * TIG_LS_REMOTE::
 *      Set command for retrieving all repository references. The command
 *      should output data in the same format as git-ls-remote(1).
 **/

#define TIG_LS_REMOTE \
        "git ls-remote . 2>/dev/null"

/**
 * [[view-commands]]
 * View commands
 * ~~~~~~~~~~~~~
 * It is possible to alter which commands are used for the different views.
 * If for example you prefer commits in the main view to be sorted by date
 * and only show 500 commits, use:
 *
 *      $ TIG_MAIN_CMD="git log --date-order -n500 --pretty=raw %s" tig
 *
 * Or set the variable permanently in your environment.
 *
 * Notice, how `%s` is used to specify the commit reference. There can
 * be a maximum of 5 `%s` ref specifications.
 *
 * TIG_DIFF_CMD::
 *      The command used for the diff view. By default, git show is used
 *      as a backend.
 *
 * TIG_LOG_CMD::
 *      The command used for the log view. If you prefer to have both
 *      author and committer shown in the log view be sure to pass
 *      `--pretty=fuller` to git log.
 *
 * TIG_MAIN_CMD::
 *      The command used for the main view. Note, you must always specify
 *      the option: `--pretty=raw` since the main view parser expects to
 *      read that format.
 **/

#define TIG_DIFF_CMD \
        "git show --patch-with-stat --find-copies-harder -B -C %s"

#define TIG_LOG_CMD     \
        "git log --cc --stat -n100 %s"

#define TIG_MAIN_CMD \
        "git log --topo-order --stat --pretty=raw %s"

/* ... silently ignore that the following are also exported. */

#define TIG_HELP_CMD \
        "man tig 2>/dev/null"

#define TIG_PAGER_CMD \
        ""


/*
 * Line-oriented content detection.
 */

#define LINE_INFO \
/*   Line type     String to match      Foreground      Background      Attributes
 *   ---------     ---------------      ----------      ----------      ---------- */ \
/* Diff markup */ \
LINE(DIFF,         "diff --git ",       COLOR_YELLOW,   COLOR_DEFAULT,  0), \
LINE(DIFF_INDEX,   "index ",            COLOR_BLUE,     COLOR_DEFAULT,  0), \
LINE(DIFF_CHUNK,   "@@",                COLOR_MAGENTA,  COLOR_DEFAULT,  0), \
LINE(DIFF_ADD,     "+",                 COLOR_GREEN,    COLOR_DEFAULT,  0), \
LINE(DIFF_DEL,     "-",                 COLOR_RED,      COLOR_DEFAULT,  0), \
LINE(DIFF_OLDMODE, "old file mode ",    COLOR_YELLOW,   COLOR_DEFAULT,  0), \
LINE(DIFF_NEWMODE, "new file mode ",    COLOR_YELLOW,   COLOR_DEFAULT,  0), \
LINE(DIFF_COPY,    "copy ",             COLOR_YELLOW,   COLOR_DEFAULT,  0), \
LINE(DIFF_RENAME,  "rename ",           COLOR_YELLOW,   COLOR_DEFAULT,  0), \
LINE(DIFF_SIM,     "similarity ",       COLOR_YELLOW,   COLOR_DEFAULT,  0), \
LINE(DIFF_DISSIM,  "dissimilarity ",    COLOR_YELLOW,   COLOR_DEFAULT,  0), \
/* Pretty print commit header */ \
LINE(PP_AUTHOR,    "Author: ",          COLOR_CYAN,     COLOR_DEFAULT,  0), \
LINE(PP_COMMIT,    "Commit: ",          COLOR_MAGENTA,  COLOR_DEFAULT,  0), \
LINE(PP_MERGE,     "Merge: ",           COLOR_BLUE,     COLOR_DEFAULT,  0), \
LINE(PP_DATE,      "Date:   ",          COLOR_YELLOW,   COLOR_DEFAULT,  0), \
LINE(PP_ADATE,     "AuthorDate: ",      COLOR_YELLOW,   COLOR_DEFAULT,  0), \
LINE(PP_CDATE,     "CommitDate: ",      COLOR_YELLOW,   COLOR_DEFAULT,  0), \
/* Raw commit header */ \
LINE(COMMIT,       "commit ",           COLOR_GREEN,    COLOR_DEFAULT,  0), \
LINE(PARENT,       "parent ",           COLOR_BLUE,     COLOR_DEFAULT,  0), \
LINE(TREE,         "tree ",             COLOR_BLUE,     COLOR_DEFAULT,  0), \
LINE(AUTHOR,       "author ",           COLOR_CYAN,     COLOR_DEFAULT,  0), \
LINE(COMMITTER,    "committer ",        COLOR_MAGENTA,  COLOR_DEFAULT,  0), \
/* Misc */ \
LINE(DIFF_TREE,    "diff-tree ",        COLOR_BLUE,     COLOR_DEFAULT,  0), \
LINE(SIGNOFF,      "    Signed-off-by", COLOR_YELLOW,   COLOR_DEFAULT,  0), \
/* UI colors */ \
LINE(DEFAULT,      "",                  COLOR_DEFAULT,  COLOR_DEFAULT,  A_NORMAL), \
LINE(CURSOR,       "",                  COLOR_WHITE,    COLOR_GREEN,    A_BOLD), \
LINE(STATUS,       "",                  COLOR_GREEN,    COLOR_DEFAULT,  0), \
LINE(TITLE_BLUR,   "",                  COLOR_WHITE,    COLOR_BLUE,     0), \
LINE(TITLE_FOCUS,  "",                  COLOR_WHITE,    COLOR_BLUE,     A_BOLD), \
LINE(MAIN_DATE,    "",                  COLOR_BLUE,     COLOR_DEFAULT,  0), \
LINE(MAIN_AUTHOR,  "",                  COLOR_GREEN,    COLOR_DEFAULT,  0), \
LINE(MAIN_COMMIT,  "",                  COLOR_DEFAULT,  COLOR_DEFAULT,  0), \
LINE(MAIN_DELIM,   "",                  COLOR_MAGENTA,  COLOR_DEFAULT,  0), \
LINE(MAIN_TAG,     "",                  COLOR_MAGENTA,  COLOR_DEFAULT,  A_BOLD), \
LINE(MAIN_REF,     "",                  COLOR_CYAN,     COLOR_DEFAULT,  A_BOLD),

enum line_type {
#define LINE(type, line, fg, bg, attr) \
        LINE_##type
        LINE_INFO
#undef  LINE
};

struct line_info {
        const char *line;       /* The start of line to match. */
        int linelen;            /* Size of string to match. */
        int fg, bg, attr;       /* Color and text attributes for the lines. */
};

static struct line_info line_info[] = {
#define LINE(type, line, fg, bg, attr) \
        { (line), STRING_SIZE(line), (fg), (bg), (attr) }
        LINE_INFO
#undef  LINE
};

static enum line_type
get_line_type(char *line)
{
        int linelen = strlen(line);
        enum line_type type;

        for (type = 0; type < ARRAY_SIZE(line_info); type++)
                /* Case insensitive search matches Signed-off-by lines better. */
                if (linelen >= line_info[type].linelen &&
                    !strncasecmp(line_info[type].line, line, line_info[type].linelen))
                        return type;

        return LINE_DEFAULT;
}

static inline int
get_line_attr(enum line_type type)
{
        assert(type < ARRAY_SIZE(line_info));
        return COLOR_PAIR(type) | line_info[type].attr;
}

static void
init_colors(void)
{
        int default_bg = COLOR_BLACK;
        int default_fg = COLOR_WHITE;
        enum line_type type;

        start_color();

        if (use_default_colors() != ERR) {
                default_bg = -1;
                default_fg = -1;
        }

        for (type = 0; type < ARRAY_SIZE(line_info); type++) {
                struct line_info *info = &line_info[type];
                int bg = info->bg == COLOR_DEFAULT ? default_bg : info->bg;
                int fg = info->fg == COLOR_DEFAULT ? default_fg : info->fg;

                init_pair(type, fg, bg);
        }
}

struct line {
        enum line_type type;
        void *data;             /* User data */
};


/**
 * The viewer
 * ----------
 * The display consists of a status window on the last line of the screen and
 * one or more views. The default is to only show one view at the time but it
 * is possible to split both the main and log view to also show the commit
 * diff.
 *
 * If you are in the log view and press 'Enter' when the current line is a
 * commit line, such as:
 *
 *      commit 4d55caff4cc89335192f3e566004b4ceef572521
 *
 * You will split the view so that the log view is displayed in the top window
 * and the diff view in the bottom window. You can switch between the two
 * views by pressing 'Tab'. To maximize the log view again, simply press 'l'.
 **/

struct view;
struct view_ops;

/* The display array of active views and the index of the current view. */
static struct view *display[2];
static unsigned int current_view;

#define foreach_view(view, i) \
        for (i = 0; i < ARRAY_SIZE(display) && (view = display[i]); i++)

#define displayed_views()       (display[1] != NULL ? 2 : 1)

/**
 * Current head and commit ID
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~
 * The viewer keeps track of both what head and commit ID you are currently
 * viewing. The commit ID will follow the cursor line and change everytime time
 * you highlight a different commit. Whenever you reopen the diff view it
 * will be reloaded, if the commit ID changed.
 *
 * The head ID is used when opening the main and log view to indicate from
 * what revision to show history.
 **/

static char ref_commit[SIZEOF_REF]      = "HEAD";
static char ref_head[SIZEOF_REF]        = "HEAD";

struct view {
        const char *name;       /* View name */
        const char *cmd_fmt;    /* Default command line format */
        const char *cmd_env;    /* Command line set via environment */
        const char *id;         /* Points to either of ref_{head,commit} */

        struct view_ops *ops;   /* View operations */

        char cmd[SIZEOF_CMD];   /* Command buffer */
        char ref[SIZEOF_REF];   /* Hovered commit reference */
        char vid[SIZEOF_REF];   /* View ID. Set to id member when updating. */

        int height, width;      /* The width and height of the main window */
        WINDOW *win;            /* The main window */
        WINDOW *title;          /* The title window living below the main window */

        /* Navigation */
        unsigned long offset;   /* Offset of the window top */
        unsigned long lineno;   /* Current line number */

        /* If non-NULL, points to the view that opened this view. If this view
         * is closed tig will switch back to the parent view. */
        struct view *parent;

        /* Buffering */
        unsigned long lines;    /* Total number of lines */
        struct line *line;      /* Line index */
        unsigned int digits;    /* Number of digits in the lines member. */

        /* Loading */
        FILE *pipe;
        time_t start_time;
};

struct view_ops {
        /* What type of content being displayed. Used in the title bar. */
        const char *type;
        /* Draw one line; @lineno must be < view->height. */
        bool (*draw)(struct view *view, struct line *line, unsigned int lineno);
        /* Read one line; updates view->line. */
        bool (*read)(struct view *view, struct line *prev, char *data);
        /* Depending on view, change display based on current line. */
        bool (*enter)(struct view *view, struct line *line);
};

static struct view_ops pager_ops;
static struct view_ops main_ops;

#define VIEW_STR(name, cmd, env, ref, ops) \
        { name, cmd, #env, ref, ops }

#define VIEW_(id, name, ops, ref) \
        VIEW_STR(name, TIG_##id##_CMD,  TIG_##id##_CMD, ref, ops)

/**
 * Views
 * ~~~~~
 * tig(1) presents various 'views' of a repository. Each view is based on output
 * from an external command, most often 'git log', 'git diff', or 'git show'.
 *
 * The main view::
 *      Is the default view, and it shows a one line summary of each commit
 *      in the chosen list of revisions. The summary includes commit date,
 *      author, and the first line of the log message. Additionally, any
 *      repository references, such as tags, will be shown.
 *
 * The log view::
 *      Presents a more rich view of the revision log showing the whole log
 *      message and the diffstat.
 *
 * The diff view::
 *      Shows either the diff of the current working tree, that is, what
 *      has changed since the last commit, or the commit diff complete
 *      with log message, diffstat and diff.
 *
 * The pager view::
 *      Is used for displaying both input from stdin and output from git
 *      commands entered in the internal prompt.
 *
 * The help view::
 *      Displays the information from the tig(1) man page. For the help view
 *      to work you need to have the tig(1) man page installed.
 **/

static struct view views[] = {
        VIEW_(MAIN,  "main",  &main_ops,  ref_head),
        VIEW_(DIFF,  "diff",  &pager_ops, ref_commit),
        VIEW_(LOG,   "log",   &pager_ops, ref_head),
        VIEW_(HELP,  "help",  &pager_ops, "static"),
        VIEW_(PAGER, "pager", &pager_ops, "static"),
};

#define VIEW(req) (&views[(req) - REQ_OFFSET - 1])


static bool
draw_view_line(struct view *view, unsigned int lineno)
{
        if (view->offset + lineno >= view->lines)
                return FALSE;

        return view->ops->draw(view, &view->line[view->offset + lineno], lineno);
}

static void
redraw_view_from(struct view *view, int lineno)
{
        assert(0 <= lineno && lineno < view->height);

        for (; lineno < view->height; lineno++) {
                if (!draw_view_line(view, lineno))
                        break;
        }

        redrawwin(view->win);
        wrefresh(view->win);
}

static void
redraw_view(struct view *view)
{
        wclear(view->win);
        redraw_view_from(view, 0);
}


/**
 * Title windows
 * ~~~~~~~~~~~~~
 * Each view has a title window which shows the name of the view, current
 * commit ID if available, and where the view is positioned:
 *
 *      [main] c622eefaa485995320bc743431bae0d497b1d875 - commit 1 of 61 (1%)
 *
 * By default, the title of the current view is highlighted using bold font.
 **/

static void
update_view_title(struct view *view)
{
        if (view == display[current_view])
                wbkgdset(view->title, get_line_attr(LINE_TITLE_FOCUS));
        else
                wbkgdset(view->title, get_line_attr(LINE_TITLE_BLUR));

        werase(view->title);
        wmove(view->title, 0, 0);

        if (*view->ref)
                wprintw(view->title, "[%s] %s", view->name, view->ref);
        else
                wprintw(view->title, "[%s]", view->name);

        if (view->lines || view->pipe) {
                unsigned int lines = view->lines
                                   ? (view->lineno + 1) * 100 / view->lines
                                   : 0;

                wprintw(view->title, " - %s %d of %d (%d%%)",
                        view->ops->type,
                        view->lineno + 1,
                        view->lines,
                        lines);
        }

        if (view->pipe) {
                time_t secs = time(NULL) - view->start_time;

                /* Three git seconds are a long time ... */
                if (secs > 2)
                        wprintw(view->title, " %lds", secs);
        }


        wrefresh(view->title);
}

static void
resize_display(void)
{
        int offset, i;
        struct view *base = display[0];
        struct view *view = display[1] ? display[1] : display[0];

        /* Setup window dimensions */

        getmaxyx(stdscr, base->height, base->width);

        /* Make room for the status window. */
        base->height -= 1;

        if (view != base) {
                /* Horizontal split. */
                view->width   = base->width;
                view->height  = SCALE_SPLIT_VIEW(base->height);
                base->height -= view->height;

                /* Make room for the title bar. */
                view->height -= 1;
        }

        /* Make room for the title bar. */
        base->height -= 1;

        offset = 0;

        foreach_view (view, i) {
                if (!view->win) {
                        view->win = newwin(view->height, 0, offset, 0);
                        if (!view->win)
                                die("Failed to create %s view", view->name);

                        scrollok(view->win, TRUE);

                        view->title = newwin(1, 0, offset + view->height, 0);
                        if (!view->title)
                                die("Failed to create title window");

                } else {
                        wresize(view->win, view->height, view->width);
                        mvwin(view->win,   offset, 0);
                        mvwin(view->title, offset + view->height, 0);
                        wrefresh(view->win);
                }

                offset += view->height + 1;
        }
}

static void
redraw_display(void)
{
        struct view *view;
        int i;

        foreach_view (view, i) {
                redraw_view(view);
                update_view_title(view);
        }
}


/*
 * Navigation
 */

/* Scrolling backend */
static void
do_scroll_view(struct view *view, int lines, bool redraw)
{
        /* The rendering expects the new offset. */
        view->offset += lines;

        assert(0 <= view->offset && view->offset < view->lines);
        assert(lines);

        /* Redraw the whole screen if scrolling is pointless. */
        if (view->height < ABS(lines)) {
                redraw_view(view);

        } else {
                int line = lines > 0 ? view->height - lines : 0;
                int end = line + ABS(lines);

                wscrl(view->win, lines);

                for (; line < end; line++) {
                        if (!draw_view_line(view, line))
                                break;
                }
        }

        /* Move current line into the view. */
        if (view->lineno < view->offset) {
                view->lineno = view->offset;
                draw_view_line(view, 0);

        } else if (view->lineno >= view->offset + view->height) {
                if (view->lineno == view->offset + view->height) {
                        /* Clear the hidden line so it doesn't show if the view
                         * is scrolled up. */
                        wmove(view->win, view->height, 0);
                        wclrtoeol(view->win);
                }
                view->lineno = view->offset + view->height - 1;
                draw_view_line(view, view->lineno - view->offset);
        }

        assert(view->offset <= view->lineno && view->lineno < view->lines);

        if (!redraw)
                return;

        redrawwin(view->win);
        wrefresh(view->win);
        report("");
}

/* Scroll frontend */
static void
scroll_view(struct view *view, enum request request)
{
        int lines = 1;

        switch (request) {
        case REQ_SCROLL_PAGE_DOWN:
                lines = view->height;
        case REQ_SCROLL_LINE_DOWN:
                if (view->offset + lines > view->lines)
                        lines = view->lines - view->offset;

                if (lines == 0 || view->offset + view->height >= view->lines) {
                        report("Cannot scroll beyond the last line");
                        return;
                }
                break;

        case REQ_SCROLL_PAGE_UP:
                lines = view->height;
        case REQ_SCROLL_LINE_UP:
                if (lines > view->offset)
                        lines = view->offset;

                if (lines == 0) {
                        report("Cannot scroll beyond the first line");
                        return;
                }

                lines = -lines;
                break;

        default:
                die("request %d not handled in switch", request);
        }

        do_scroll_view(view, lines, TRUE);
}

/* Cursor moving */
static void
move_view(struct view *view, enum request request, bool redraw)
{
        int steps;

        switch (request) {
        case REQ_MOVE_FIRST_LINE:
                steps = -view->lineno;
                break;

        case REQ_MOVE_LAST_LINE:
                steps = view->lines - view->lineno - 1;
                break;

        case REQ_MOVE_PAGE_UP:
                steps = view->height > view->lineno
                      ? -view->lineno : -view->height;
                break;

        case REQ_MOVE_PAGE_DOWN:
                steps = view->lineno + view->height >= view->lines
                      ? view->lines - view->lineno - 1 : view->height;
                break;

        case REQ_MOVE_UP:
                steps = -1;
                break;

        case REQ_MOVE_DOWN:
                steps = 1;
                break;

        default:
                die("request %d not handled in switch", request);
        }

        if (steps <= 0 && view->lineno == 0) {
                report("Cannot move beyond the first line");
                return;

        } else if (steps >= 0 && view->lineno + 1 >= view->lines) {
                report("Cannot move beyond the last line");
                return;
        }

        /* Move the current line */
        view->lineno += steps;
        assert(0 <= view->lineno && view->lineno < view->lines);

        /* Repaint the old "current" line if we be scrolling */
        if (ABS(steps) < view->height) {
                int prev_lineno = view->lineno - steps - view->offset;

                wmove(view->win, prev_lineno, 0);
                wclrtoeol(view->win);
                draw_view_line(view,  prev_lineno);
        }

        /* Check whether the view needs to be scrolled */
        if (view->lineno < view->offset ||
            view->lineno >= view->offset + view->height) {
                if (steps < 0 && -steps > view->offset) {
                        steps = -view->offset;

                } else if (steps > 0) {
                        if (view->lineno == view->lines - 1 &&
                            view->lines > view->height) {
                                steps = view->lines - view->offset - 1;
                                if (steps >= view->height)
                                        steps -= view->height - 1;
                        }
                }

                do_scroll_view(view, steps, redraw);
                return;
        }

        /* Draw the current line */
        draw_view_line(view, view->lineno - view->offset);

        if (!redraw)
                return;

        redrawwin(view->win);
        wrefresh(view->win);
        report("");
}


/*
 * Incremental updating
 */

static void
end_update(struct view *view)
{
        if (!view->pipe)
                return;
        set_nonblocking_input(FALSE);
        if (view->pipe == stdin)
                fclose(view->pipe);
        else
                pclose(view->pipe);
        view->pipe = NULL;
}

static bool
begin_update(struct view *view)
{
        const char *id = view->id;

        if (view->pipe)
                end_update(view);

        if (opt_cmd[0]) {
                string_copy(view->cmd, opt_cmd);
                opt_cmd[0] = 0;
                /* When running random commands, the view ref could have become
                 * invalid so clear it. */
                view->ref[0] = 0;
        } else {
                const char *format = view->cmd_env ? view->cmd_env : view->cmd_fmt;

                if (snprintf(view->cmd, sizeof(view->cmd), format,
                             id, id, id, id, id) >= sizeof(view->cmd))
                        return FALSE;
        }

        /* Special case for the pager view. */
        if (opt_pipe) {
                view->pipe = opt_pipe;
                opt_pipe = NULL;
        } else {
                view->pipe = popen(view->cmd, "r");
        }

        if (!view->pipe)
                return FALSE;

        set_nonblocking_input(TRUE);

        view->offset = 0;
        view->lines  = 0;
        view->lineno = 0;
        string_copy(view->vid, id);

        if (view->line) {
                int i;

                for (i = 0; i < view->lines; i++)
                        if (view->line[i].data)
                                free(view->line[i].data);

                free(view->line);
                view->line = NULL;
        }

        view->start_time = time(NULL);

        return TRUE;
}

static bool
update_view(struct view *view)
{
        char buffer[BUFSIZ];
        char *line;
        struct line *tmp;
        /* The number of lines to read. If too low it will cause too much
         * redrawing (and possible flickering), if too high responsiveness
         * will suffer. */
        unsigned long lines = view->height;
        int redraw_from = -1;

        if (!view->pipe)
                return TRUE;

        /* Only redraw if lines are visible. */
        if (view->offset + view->height >= view->lines)
                redraw_from = view->lines - view->offset;

        tmp = realloc(view->line, sizeof(*view->line) * (view->lines + lines));
        if (!tmp)
                goto alloc_error;

        view->line = tmp;

        while ((line = fgets(buffer, sizeof(buffer), view->pipe))) {
                int linelen = strlen(line);

                struct line *prev = view->lines
                                  ? &view->line[view->lines - 1]
                                  : NULL;

                if (linelen)
                        line[linelen - 1] = 0;

                if (!view->ops->read(view, prev, line))
                        goto alloc_error;

                if (lines-- == 1)
                        break;
        }

        {
                int digits;

                lines = view->lines;
                for (digits = 0; lines; digits++)
                        lines /= 10;

                /* Keep the displayed view in sync with line number scaling. */
                if (digits != view->digits) {
                        view->digits = digits;
                        redraw_from = 0;
                }
        }

        if (redraw_from >= 0) {
                /* If this is an incremental update, redraw the previous line
                 * since for commits some members could have changed when
                 * loading the main view. */
                if (redraw_from > 0)
                        redraw_from--;

                /* Incrementally draw avoids flickering. */
                redraw_view_from(view, redraw_from);
        }

        /* Update the title _after_ the redraw so that if the redraw picks up a
         * commit reference in view->ref it'll be available here. */
        update_view_title(view);

        if (ferror(view->pipe)) {
                report("Failed to read: %s", strerror(errno));
                goto end;

        } else if (feof(view->pipe)) {
                if (view == VIEW(REQ_VIEW_HELP)) {
                        const char *msg = TIG_HELP;

                        if (view->lines == 0) {
                                /* Slightly ugly, but abusing view->ref keeps
                                 * the error message. */
                                string_copy(view->ref, "No help available");
                                msg = "The tig(1) manpage is not installed";
                        }

                        report("%s", msg);
                        goto end;
                }

                report("");
                goto end;
        }

        return TRUE;

alloc_error:
        report("Allocation failure");

end:
        end_update(view);
        return FALSE;
}

enum open_flags {
        OPEN_DEFAULT = 0,       /* Use default view switching. */
        OPEN_SPLIT = 1,         /* Split current view. */
        OPEN_BACKGROUNDED = 2,  /* Backgrounded. */
        OPEN_RELOAD = 4,        /* Reload view even if it is the current. */
};

static void
open_view(struct view *prev, enum request request, enum open_flags flags)
{
        bool backgrounded = !!(flags & OPEN_BACKGROUNDED);
        bool split = !!(flags & OPEN_SPLIT);
        bool reload = !!(flags & OPEN_RELOAD);
        struct view *view = VIEW(request);
        int nviews = displayed_views();
        struct view *base_view = display[0];

        if (view == prev && nviews == 1 && !reload) {
                report("Already in %s view", view->name);
                return;
        }

        if ((reload || strcmp(view->vid, view->id)) &&
            !begin_update(view)) {
                report("Failed to load %s view", view->name);
                return;
        }

        if (split) {
                display[current_view + 1] = view;
                if (!backgrounded)
                        current_view++;
        } else {
                /* Maximize the current view. */
                memset(display, 0, sizeof(display));
                current_view = 0;
                display[current_view] = view;
        }

        /* Resize the view when switching between split- and full-screen,
         * or when switching between two different full-screen views. */
        if (nviews != displayed_views() ||
            (nviews == 1 && base_view != display[0]))
                resize_display();

        if (split && prev->lineno - prev->offset >= prev->height) {
                /* Take the title line into account. */
                int lines = prev->lineno - prev->offset - prev->height + 1;

                /* Scroll the view that was split if the current line is
                 * outside the new limited view. */
                do_scroll_view(prev, lines, TRUE);
        }

        if (prev && view != prev) {
                /* Continue loading split views in the background. */
                if (!split)
                        end_update(prev);
                else if (!backgrounded)
                        /* "Blur" the previous view. */
                        update_view_title(prev);

                view->parent = prev;
        }

        if (view->pipe) {
                /* Clear the old view and let the incremental updating refill
                 * the screen. */
                wclear(view->win);
                report("");
        } else {
                redraw_view(view);
                if (view == VIEW(REQ_VIEW_HELP))
                        report("%s", TIG_HELP);
                else
                        report("");
        }

        /* If the view is backgrounded the above calls to report()
         * won't redraw the view title. */
        if (backgrounded)
                update_view_title(view);
}


/*
 * User request switch noodle
 */

static int
view_driver(struct view *view, enum request request)
{
        int i;

        switch (request) {
        case REQ_MOVE_UP:
        case REQ_MOVE_DOWN:
        case REQ_MOVE_PAGE_UP:
        case REQ_MOVE_PAGE_DOWN:
        case REQ_MOVE_FIRST_LINE:
        case REQ_MOVE_LAST_LINE:
                move_view(view, request, TRUE);
                break;

        case REQ_SCROLL_LINE_DOWN:
        case REQ_SCROLL_LINE_UP:
        case REQ_SCROLL_PAGE_DOWN:
        case REQ_SCROLL_PAGE_UP:
                scroll_view(view, request);
                break;

        case REQ_VIEW_MAIN:
        case REQ_VIEW_DIFF:
        case REQ_VIEW_LOG:
        case REQ_VIEW_HELP:
        case REQ_VIEW_PAGER:
                open_view(view, request, OPEN_DEFAULT);
                break;

        case REQ_NEXT:
        case REQ_PREVIOUS:
                request = request == REQ_NEXT ? REQ_MOVE_DOWN : REQ_MOVE_UP;

                if (view == VIEW(REQ_VIEW_DIFF) &&
                    view->parent == VIEW(REQ_VIEW_MAIN)) {
                        bool redraw = display[1] == view;

                        view = view->parent;
                        move_view(view, request, redraw);
                        if (redraw)
                                update_view_title(view);
                } else {
                        move_view(view, request, TRUE);
                        break;
                }
                /* Fall-through */

        case REQ_ENTER:
                if (!view->lines) {
                        report("Nothing to enter");
                        break;
                }
                return view->ops->enter(view, &view->line[view->lineno]);

        case REQ_VIEW_NEXT:
        {
                int nviews = displayed_views();
                int next_view = (current_view + 1) % nviews;

                if (next_view == current_view) {
                        report("Only one view is displayed");
                        break;
                }

                current_view = next_view;
                /* Blur out the title of the previous view. */
                update_view_title(view);
                report("");
                break;
        }
        case REQ_TOGGLE_LINE_NUMBERS:
                opt_line_number = !opt_line_number;
                redraw_display();
                break;

        case REQ_PROMPT:
                /* Always reload^Wrerun commands from the prompt. */
                open_view(view, opt_request, OPEN_RELOAD);
                break;

        case REQ_STOP_LOADING:
                foreach_view (view, i) {
                        if (view->pipe)
                                report("Stopped loaded the %s view", view->name),
                        end_update(view);
                }
                break;

        case REQ_SHOW_VERSION:
                report("%s (built %s)", VERSION, __DATE__);
                return TRUE;

        case REQ_SCREEN_RESIZE:
                resize_display();
                /* Fall-through */
        case REQ_SCREEN_REDRAW:
                redraw_display();
                break;

        case REQ_SCREEN_UPDATE:
                doupdate();
                return TRUE;

        case REQ_VIEW_CLOSE:
                if (view->parent) {
                        memset(display, 0, sizeof(display));
                        current_view = 0;
                        display[current_view] = view->parent;
                        view->parent = NULL;
                        resize_display();
                        redraw_display();
                        break;
                }
                /* Fall-through */
        case REQ_QUIT:
                return FALSE;

        default:
                /* An unknown key will show most commonly used commands. */
                report("Unknown key, press 'h' for help");
                return TRUE;
        }

        return TRUE;
}


/*
 * Pager backend
 */

static bool
pager_draw(struct view *view, struct line *line, unsigned int lineno)
{
        char *text = line->data;
        enum line_type type = line->type;
        int textlen = strlen(text);
        int attr;

        wmove(view->win, lineno, 0);

        if (view->offset + lineno == view->lineno) {
                if (type == LINE_COMMIT) {
                        string_copy(view->ref, text + 7);
                        string_copy(ref_commit, view->ref);
                }

                type = LINE_CURSOR;
                wchgat(view->win, -1, 0, type, NULL);
        }

        attr = get_line_attr(type);
        wattrset(view->win, attr);

        if (opt_line_number || opt_tab_size < TABSIZE) {
                static char spaces[] = "                    ";
                int col_offset = 0, col = 0;

                if (opt_line_number) {
                        unsigned long real_lineno = view->offset + lineno + 1;

                        if (real_lineno == 1 ||
                            (real_lineno % opt_num_interval) == 0) {
                                wprintw(view->win, "%.*d", view->digits, real_lineno);

                        } else {
                                waddnstr(view->win, spaces,
                                         MIN(view->digits, STRING_SIZE(spaces)));
                        }
                        waddstr(view->win, ": ");
                        col_offset = view->digits + 2;
                }

                while (text && col_offset + col < view->width) {
                        int cols_max = view->width - col_offset - col;
                        char *pos = text;
                        int cols;

                        if (*text == '\t') {
                                text++;
                                assert(sizeof(spaces) > TABSIZE);
                                pos = spaces;
                                cols = opt_tab_size - (col % opt_tab_size);

                        } else {
                                text = strchr(text, '\t');
                                cols = line ? text - pos : strlen(pos);
                        }

                        waddnstr(view->win, pos, MIN(cols, cols_max));
                        col += cols;
                }

        } else {
                int col = 0, pos = 0;

                for (; pos < textlen && col < view->width; pos++, col++)
                        if (text[pos] == '\t')
                                col += TABSIZE - (col % TABSIZE) - 1;

                waddnstr(view->win, text, pos);
        }

        return TRUE;
}

static bool
pager_read(struct view *view, struct line *prev, char *line)
{
        /* Compress empty lines in the help view. */
        if (view == VIEW(REQ_VIEW_HELP) &&
            !*line && prev && !*((char *) prev->data))
                return TRUE;

        view->line[view->lines].data = strdup(line);
        if (!view->line[view->lines].data)
                return FALSE;

        view->line[view->lines].type = get_line_type(line);

        view->lines++;
        return TRUE;
}

static bool
pager_enter(struct view *view, struct line *line)
{
        int split = 0;

        if (line->type == LINE_COMMIT &&
           (view == VIEW(REQ_VIEW_LOG) ||
            view == VIEW(REQ_VIEW_PAGER))) {
                open_view(view, REQ_VIEW_DIFF, OPEN_SPLIT);
                split = 1;
        }

        /* Always scroll the view even if it was split. That way
         * you can use Enter to scroll through the log view and
         * split open each commit diff. */
        scroll_view(view, REQ_SCROLL_LINE_DOWN);

        /* FIXME: A minor workaround. Scrolling the view will call report("")
         * but if we are scolling a non-current view this won't properly update
         * the view title. */
        if (split)
                update_view_title(view);

        return TRUE;
}

static struct view_ops pager_ops = {
        "line",
        pager_draw,
        pager_read,
        pager_enter,
};


/*
 * Main view backend
 */

struct commit {
        char id[41];            /* SHA1 ID. */
        char title[75];         /* The first line of the commit message. */
        char author[75];        /* The author of the commit. */
        struct tm time;         /* Date from the author ident. */
        struct ref **refs;      /* Repository references; tags & branch heads. */
};

static bool
main_draw(struct view *view, struct line *line, unsigned int lineno)
{
        char buf[DATE_COLS + 1];
        struct commit *commit = line->data;
        enum line_type type;
        int col = 0;
        size_t timelen;
        size_t authorlen;
        int trimmed;

        if (!*commit->author)
                return FALSE;

        wmove(view->win, lineno, col);

        if (view->offset + lineno == view->lineno) {
                string_copy(view->ref, commit->id);
                string_copy(ref_commit, view->ref);
                type = LINE_CURSOR;
                wattrset(view->win, get_line_attr(type));
                wchgat(view->win, -1, 0, type, NULL);

        } else {
                type = LINE_MAIN_COMMIT;
                wattrset(view->win, get_line_attr(LINE_MAIN_DATE));
        }

        timelen = strftime(buf, sizeof(buf), DATE_FORMAT, &commit->time);
        waddnstr(view->win, buf, timelen);
        waddstr(view->win, " ");

        col += DATE_COLS;
        wmove(view->win, lineno, col);
        if (type != LINE_CURSOR)
                wattrset(view->win, get_line_attr(LINE_MAIN_AUTHOR));

        /* FIXME: Make this optional, and add i18n.commitEncoding support. */
        authorlen = utf8_length(commit->author, AUTHOR_COLS - 2, &col, &trimmed);

        if (trimmed) {
                waddnstr(view->win, commit->author, authorlen);
                if (type != LINE_CURSOR)
                        wattrset(view->win, get_line_attr(LINE_MAIN_DELIM));
                waddch(view->win, '~');
        } else {
                waddstr(view->win, commit->author);
        }

        col += AUTHOR_COLS;
        if (type != LINE_CURSOR)
                wattrset(view->win, A_NORMAL);

        mvwaddch(view->win, lineno, col, ACS_LTEE);
        wmove(view->win, lineno, col + 2);
        col += 2;

        if (commit->refs) {
                size_t i = 0;

                do {
                        if (type == LINE_CURSOR)
                                ;
                        else if (commit->refs[i]->tag)
                                wattrset(view->win, get_line_attr(LINE_MAIN_TAG));
                        else
                                wattrset(view->win, get_line_attr(LINE_MAIN_REF));
                        waddstr(view->win, "[");
                        waddstr(view->win, commit->refs[i]->name);
                        waddstr(view->win, "]");
                        if (type != LINE_CURSOR)
                                wattrset(view->win, A_NORMAL);
                        waddstr(view->win, " ");
                        col += strlen(commit->refs[i]->name) + STRING_SIZE("[] ");
                } while (commit->refs[i++]->next);
        }

        if (type != LINE_CURSOR)
                wattrset(view->win, get_line_attr(type));

        {
                int titlelen = strlen(commit->title);

                if (col + titlelen > view->width)
                        titlelen = view->width - col;

                waddnstr(view->win, commit->title, titlelen);
        }

        return TRUE;
}

/* Reads git log --pretty=raw output and parses it into the commit struct. */
static bool
main_read(struct view *view, struct line *prev, char *line)
{
        enum line_type type = get_line_type(line);
        struct commit *commit;

        switch (type) {
        case LINE_COMMIT:
                commit = calloc(1, sizeof(struct commit));
                if (!commit)
                        return FALSE;

                line += STRING_SIZE("commit ");

                view->line[view->lines++].data = commit;
                string_copy(commit->id, line);
                commit->refs = get_refs(commit->id);
                break;

        case LINE_AUTHOR:
        {
                char *ident = line + STRING_SIZE("author ");
                char *end = strchr(ident, '<');

                if (!prev)
                        break;

                commit = prev->data;

                if (end) {
                        for (; end > ident && isspace(end[-1]); end--) ;
                        *end = 0;
                }

                string_copy(commit->author, ident);

                /* Parse epoch and timezone */
                if (end) {
                        char *secs = strchr(end + 1, '>');
                        char *zone;
                        time_t time;

                        if (!secs || secs[1] != ' ')
                                break;

                        secs += 2;
                        time = (time_t) atol(secs);
                        zone = strchr(secs, ' ');
                        if (zone && strlen(zone) == STRING_SIZE(" +0700")) {
                                long tz;

                                zone++;
                                tz  = ('0' - zone[1]) * 60 * 60 * 10;
                                tz += ('0' - zone[2]) * 60 * 60;
                                tz += ('0' - zone[3]) * 60;
                                tz += ('0' - zone[4]) * 60;

                                if (zone[0] == '-')
                                        tz = -tz;

                                time -= tz;
                        }
                        gmtime_r(&time, &commit->time);
                }
                break;
        }
        default:
                if (!prev)
                        break;

                commit = prev->data;

                /* Fill in the commit title if it has not already been set. */
                if (commit->title[0])
                        break;

                /* Require titles to start with a non-space character at the
                 * offset used by git log. */
                /* FIXME: More gracefull handling of titles; append "..." to
                 * shortened titles, etc. */
                if (strncmp(line, "    ", 4) ||
                    isspace(line[4]))
                        break;

                string_copy(commit->title, line + 4);
        }

        return TRUE;
}

static bool
main_enter(struct view *view, struct line *line)
{
        enum open_flags flags = display[0] == view ? OPEN_SPLIT : OPEN_DEFAULT;

        open_view(view, REQ_VIEW_DIFF, flags);
        return TRUE;
}

static struct view_ops main_ops = {
        "commit",
        main_draw,
        main_read,
        main_enter,
};


/**
 * KEYS
 * ----
 * Below the default key bindings are shown.
 **/

struct keymap {
        int alias;
        int request;
};

static struct keymap keymap[] = {
        /**
         * View switching
         * ~~~~~~~~~~~~~~
         * m::
         *      Switch to main view.
         * d::
         *      Switch to diff view.
         * l::
         *      Switch to log view.
         * p::
         *      Switch to pager view.
         * h::
         *      Show man page.
         **/
        { 'm',          REQ_VIEW_MAIN },
        { 'd',          REQ_VIEW_DIFF },
        { 'l',          REQ_VIEW_LOG },
        { 'p',          REQ_VIEW_PAGER },
        { 'h',          REQ_VIEW_HELP },

        /**
         * View manipulation
         * ~~~~~~~~~~~~~~~~~
         * q::
         *      Close view, if multiple views are open it will jump back to the
         *      previous view in the view stack. If it is the last open view it
         *      will quit. Use 'Q' to quit all views at once.
         * Enter::
         *      This key is "context sensitive" depending on what view you are
         *      currently in. When in log view on a commit line or in the main
         *      view, split the view and show the commit diff. In the diff view
         *      pressing Enter will simply scroll the view one line down.
         * Tab::
         *      Switch to next view.
         * Up::
         *      This key is "context sensitive" and will move the cursor one
         *      line up. However, uf you opened a diff view from the main view
         *      (split- or full-screen) it will change the cursor to point to
         *      the previous commit in the main view and update the diff view
         *      to display it.
         * Down::
         *      Similar to 'Up' but will move down.
         **/
        { 'q',          REQ_VIEW_CLOSE },
        { KEY_TAB,      REQ_VIEW_NEXT },
        { KEY_RETURN,   REQ_ENTER },
        { KEY_UP,       REQ_PREVIOUS },
        { KEY_DOWN,     REQ_NEXT },

        /**
         * Cursor navigation
         * ~~~~~~~~~~~~~~~~~
         * j::
         *      Move cursor one line up.
         * k::
         *      Move cursor one line down.
         * PgUp::
         * b::
         * -::
         *      Move cursor one page up.
         * PgDown::
         * Space::
         *      Move cursor one page down.
         * Home::
         *      Jump to first line.
         * End::
         *      Jump to last line.
         **/
        { 'k',          REQ_MOVE_UP },
        { 'j',          REQ_MOVE_DOWN },
        { KEY_HOME,     REQ_MOVE_FIRST_LINE },
        { KEY_END,      REQ_MOVE_LAST_LINE },
        { KEY_NPAGE,    REQ_MOVE_PAGE_DOWN },
        { ' ',          REQ_MOVE_PAGE_DOWN },
        { KEY_PPAGE,    REQ_MOVE_PAGE_UP },
        { 'b',          REQ_MOVE_PAGE_UP },
        { '-',          REQ_MOVE_PAGE_UP },

        /**
         * Scrolling
         * ~~~~~~~~~
         * Insert::
         *      Scroll view one line up.
         * Delete::
         *      Scroll view one line down.
         * w::
         *      Scroll view one page up.
         * s::
         *      Scroll view one page down.
         **/
        { KEY_IC,       REQ_SCROLL_LINE_UP },
        { KEY_DC,       REQ_SCROLL_LINE_DOWN },
        { 'w',          REQ_SCROLL_PAGE_UP },
        { 's',          REQ_SCROLL_PAGE_DOWN },

        /**
         * Misc
         * ~~~~
         * Q::
         *      Quit.
         * r::
         *      Redraw screen.
         * z::
         *      Stop all background loading. This can be useful if you use
         *      tig(1) in a repository with a long history without limiting
         *      the revision log.
         * v::
         *      Show version.
         * n::
         *      Toggle line numbers on/off.
         * ':'::
         *      Open prompt. This allows you to specify what git command
         *      to run. Example:
         *
         *      :log -p
         **/
        { 'Q',          REQ_QUIT },
        { 'z',          REQ_STOP_LOADING },
        { 'v',          REQ_SHOW_VERSION },
        { 'r',          REQ_SCREEN_REDRAW },
        { 'n',          REQ_TOGGLE_LINE_NUMBERS },
        { ':',          REQ_PROMPT },

        /* wgetch() with nodelay() enabled returns ERR when there's no input. */
        { ERR,          REQ_SCREEN_UPDATE },

        /* Use the ncurses SIGWINCH handler. */
        { KEY_RESIZE,   REQ_SCREEN_RESIZE },
};

static enum request
get_request(int key)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(keymap); i++)
                if (keymap[i].alias == key)
                        return keymap[i].request;

        return (enum request) key;
}


/*
 * Unicode / UTF-8 handling
 *
 * NOTE: Much of the following code for dealing with unicode is derived from
 * ELinks' UTF-8 code developed by Scrool <scroolik@gmail.com>. Origin file is
 * src/intl/charset.c from the utf8 branch commit elinks-0.11.0-g31f2c28.
 */

/* I've (over)annotated a lot of code snippets because I am not entirely
 * confident that the approach taken by this small UTF-8 interface is correct.
 * --jonas */

static inline int
unicode_width(unsigned long c)
{
        if (c >= 0x1100 &&
           (c <= 0x115f                         /* Hangul Jamo */
            || c == 0x2329
            || c == 0x232a
            || (c >= 0x2e80  && c <= 0xa4cf && c != 0x303f)
                                                /* CJK ... Yi */
            || (c >= 0xac00  && c <= 0xd7a3)    /* Hangul Syllables */
            || (c >= 0xf900  && c <= 0xfaff)    /* CJK Compatibility Ideographs */
            || (c >= 0xfe30  && c <= 0xfe6f)    /* CJK Compatibility Forms */
            || (c >= 0xff00  && c <= 0xff60)    /* Fullwidth Forms */
            || (c >= 0xffe0  && c <= 0xffe6)
            || (c >= 0x20000 && c <= 0x2fffd)
            || (c >= 0x30000 && c <= 0x3fffd)))
                return 2;

        return 1;
}

/* Number of bytes used for encoding a UTF-8 character indexed by first byte.
 * Illegal bytes are set one. */
static const unsigned char utf8_bytes[256] = {
        1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
        1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
        1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
        1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
        1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
        1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
        2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2,
        3,3,3,3,3,3,3,3, 3,3,3,3,3,3,3,3, 4,4,4,4,4,4,4,4, 5,5,5,5,6,6,1,1,
};

/* Decode UTF-8 multi-byte representation into a unicode character. */
static inline unsigned long
utf8_to_unicode(const char *string, size_t length)
{
        unsigned long unicode;

        switch (length) {
        case 1:
                unicode  =   string[0];
                break;
        case 2:
                unicode  =  (string[0] & 0x1f) << 6;
                unicode +=  (string[1] & 0x3f);
                break;
        case 3:
                unicode  =  (string[0] & 0x0f) << 12;
                unicode += ((string[1] & 0x3f) << 6);
                unicode +=  (string[2] & 0x3f);
                break;
        case 4:
                unicode  =  (string[0] & 0x0f) << 18;
                unicode += ((string[1] & 0x3f) << 12);
                unicode += ((string[2] & 0x3f) << 6);
                unicode +=  (string[3] & 0x3f);
                break;
        case 5:
                unicode  =  (string[0] & 0x0f) << 24;
                unicode += ((string[1] & 0x3f) << 18);
                unicode += ((string[2] & 0x3f) << 12);
                unicode += ((string[3] & 0x3f) << 6);
                unicode +=  (string[4] & 0x3f);
                break;
        case 6:
                unicode  =  (string[0] & 0x01) << 30;
                unicode += ((string[1] & 0x3f) << 24);
                unicode += ((string[2] & 0x3f) << 18);
                unicode += ((string[3] & 0x3f) << 12);
                unicode += ((string[4] & 0x3f) << 6);
                unicode +=  (string[5] & 0x3f);
                break;
        default:
                die("Invalid unicode length");
        }

        /* Invalid characters could return the special 0xfffd value but NUL
         * should be just as good. */
        return unicode > 0xffff ? 0 : unicode;
}

/* Calculates how much of string can be shown within the given maximum width
 * and sets trimmed parameter to non-zero value if all of string could not be
 * shown.
 *
 * Additionally, adds to coloffset how many many columns to move to align with
 * the expected position. Takes into account how multi-byte and double-width
 * characters will effect the cursor position.
 *
 * Returns the number of bytes to output from string to satisfy max_width. */
static size_t
utf8_length(const char *string, size_t max_width, int *coloffset, int *trimmed)
{
        const char *start = string;
        const char *end = strchr(string, '\0');
        size_t mbwidth = 0;
        size_t width = 0;

        *trimmed = 0;

        while (string < end) {
                int c = *(unsigned char *) string;
                unsigned char bytes = utf8_bytes[c];
                size_t ucwidth;
                unsigned long unicode;

                if (string + bytes > end)
                        break;

                /* Change representation to figure out whether
                 * it is a single- or double-width character. */

                unicode = utf8_to_unicode(string, bytes);
                /* FIXME: Graceful handling of invalid unicode character. */
                if (!unicode)
                        break;

                ucwidth = unicode_width(unicode);
                width  += ucwidth;
                if (width > max_width) {
                        *trimmed = 1;
                        break;
                }

                /* The column offset collects the differences between the
                 * number of bytes encoding a character and the number of
                 * columns will be used for rendering said character.
                 *
                 * So if some character A is encoded in 2 bytes, but will be
                 * represented on the screen using only 1 byte this will and up
                 * adding 1 to the multi-byte column offset.
                 *
                 * Assumes that no double-width character can be encoding in
                 * less than two bytes. */
                if (bytes > ucwidth)
                        mbwidth += bytes - ucwidth;

                string  += bytes;
        }

        *coloffset += mbwidth;

        return string - start;
}


/*
 * Status management
 */

/* Whether or not the curses interface has been initialized. */
static bool cursed = FALSE;

/* The status window is used for polling keystrokes. */
static WINDOW *status_win;

/* Update status and title window. */
static void
report(const char *msg, ...)
{
        static bool empty = TRUE;
        struct view *view = display[current_view];

        if (!empty || *msg) {
                va_list args;

                va_start(args, msg);

                werase(status_win);
                wmove(status_win, 0, 0);
                if (*msg) {
                        vwprintw(status_win, msg, args);
                        empty = FALSE;
                } else {
                        empty = TRUE;
                }
                wrefresh(status_win);

                va_end(args);
        }

        update_view_title(view);

        /* Move the cursor to the right-most column of the cursor line.
         *
         * XXX: This could turn out to be a bit expensive, but it ensures that
         * the cursor does not jump around. */
        if (view->lines) {
                wmove(view->win, view->lineno - view->offset, view->width - 1);
                wrefresh(view->win);
        }
}

/* Controls when nodelay should be in effect when polling user input. */
static void
set_nonblocking_input(bool loading)
{
        static unsigned int loading_views;

        if ((loading == FALSE && loading_views-- == 1) ||
            (loading == TRUE  && loading_views++ == 0))
                nodelay(status_win, loading);
}

static void
init_display(void)
{
        int x, y;

        /* Initialize the curses library */
        if (isatty(STDIN_FILENO)) {
                cursed = !!initscr();
        } else {
                /* Leave stdin and stdout alone when acting as a pager. */
                FILE *io = fopen("/dev/tty", "r+");

                cursed = !!newterm(NULL, io, io);
        }

        if (!cursed)
                die("Failed to initialize curses");

        nonl();         /* Tell curses not to do NL->CR/NL on output */
        cbreak();       /* Take input chars one at a time, no wait for \n */
        noecho();       /* Don't echo input */
        leaveok(stdscr, TRUE);

        if (has_colors())
                init_colors();

        getmaxyx(stdscr, y, x);
        status_win = newwin(1, 0, y - 1, 0);
        if (!status_win)
                die("Failed to create status window");

        /* Enable keyboard mapping */
        keypad(status_win, TRUE);
        wbkgdset(status_win, get_line_attr(LINE_STATUS));
}


/*
 * Repository references
 */

static struct ref *refs;
static size_t refs_size;

/* Id <-> ref store */
static struct ref ***id_refs;
static size_t id_refs_size;

static struct ref **
get_refs(char *id)
{
        struct ref ***tmp_id_refs;
        struct ref **ref_list = NULL;
        size_t ref_list_size = 0;
        size_t i;

        for (i = 0; i < id_refs_size; i++)
                if (!strcmp(id, id_refs[i][0]->id))
                        return id_refs[i];

        tmp_id_refs = realloc(id_refs, (id_refs_size + 1) * sizeof(*id_refs));
        if (!tmp_id_refs)
                return NULL;

        id_refs = tmp_id_refs;

        for (i = 0; i < refs_size; i++) {
                struct ref **tmp;

                if (strcmp(id, refs[i].id))
                        continue;

                tmp = realloc(ref_list, (ref_list_size + 1) * sizeof(*ref_list));
                if (!tmp) {
                        if (ref_list)
                                free(ref_list);
                        return NULL;
                }

                ref_list = tmp;
                if (ref_list_size > 0)
                        ref_list[ref_list_size - 1]->next = 1;
                ref_list[ref_list_size] = &refs[i];

                /* XXX: The properties of the commit chains ensures that we can
                 * safely modify the shared ref. The repo references will
                 * always be similar for the same id. */
                ref_list[ref_list_size]->next = 0;
                ref_list_size++;
        }

        if (ref_list)
                id_refs[id_refs_size++] = ref_list;

        return ref_list;
}

static int
load_refs(void)
{
        const char *cmd_env = getenv("TIG_LS_REMOTE");
        const char *cmd = cmd_env && *cmd_env ? cmd_env : TIG_LS_REMOTE;
        FILE *pipe = popen(cmd, "r");
        char buffer[BUFSIZ];
        char *line;

        if (!pipe)
                return ERR;

        while ((line = fgets(buffer, sizeof(buffer), pipe))) {
                char *name = strchr(line, '\t');
                struct ref *ref;
                int namelen;
                bool tag = FALSE;
                bool tag_commit = FALSE;

                if (!name)
                        continue;

                *name++ = 0;
                namelen = strlen(name) - 1;

                /* Commits referenced by tags has "^{}" appended. */
                if (name[namelen - 1] == '}') {
                        while (namelen > 0 && name[namelen] != '^')
                                namelen--;
                        if (namelen > 0)
                                tag_commit = TRUE;
                }
                name[namelen] = 0;

                if (!strncmp(name, "refs/tags/", STRING_SIZE("refs/tags/"))) {
                        if (!tag_commit)
                                continue;
                        name += STRING_SIZE("refs/tags/");
                        tag = TRUE;

                } else if (!strncmp(name, "refs/heads/", STRING_SIZE("refs/heads/"))) {
                        name += STRING_SIZE("refs/heads/");

                } else if (!strcmp(name, "HEAD")) {
                        continue;
                }

                refs = realloc(refs, sizeof(*refs) * (refs_size + 1));
                if (!refs)
                        return ERR;

                ref = &refs[refs_size++];
                ref->tag = tag;
                ref->name = strdup(name);
                if (!ref->name)
                        return ERR;

                string_copy(ref->id, line);
        }

        if (ferror(pipe))
                return ERR;

        pclose(pipe);

        return OK;
}

static int
load_config(void)
{
        FILE *pipe = popen("git repo-config --list", "r");
        char buffer[BUFSIZ];
        char *name;

        if (!pipe)
                return ERR;

        while ((name = fgets(buffer, sizeof(buffer), pipe))) {
                char *value = strchr(name, '=');
                int valuelen, namelen;

                /* No boolean options, yet */
                if (!value)
                        continue;

                namelen  = value - name;

                *value++ = 0;
                valuelen = strlen(value);
                if (valuelen > 0)
                        value[valuelen - 1] = 0;

                if (!strcmp(name, "i18n.commitencoding")) {
                        string_copy(opt_encoding, value);
                }
        }

        if (ferror(pipe))
                return ERR;

        pclose(pipe);

        return OK;
}

/*
 * Main
 */

#if __GNUC__ >= 3
#define __NORETURN __attribute__((__noreturn__))
#else
#define __NORETURN
#endif

static void __NORETURN
quit(int sig)
{
        /* XXX: Restore tty modes and let the OS cleanup the rest! */
        if (cursed)
                endwin();
        exit(0);
}

static void __NORETURN
die(const char *err, ...)
{
        va_list args;

        endwin();

        va_start(args, err);
        fputs("tig: ", stderr);
        vfprintf(stderr, err, args);
        fputs("\n", stderr);
        va_end(args);

        exit(1);
}

int
main(int argc, char *argv[])
{
        struct view *view;
        enum request request;
        size_t i;

        signal(SIGINT, quit);

        if (!parse_options(argc, argv))
                return 0;

        if (load_refs() == ERR)
                die("Failed to load refs.");

        /* Require a git repository unless when running in pager mode. */
        if (refs_size == 0 && opt_request != REQ_VIEW_PAGER)
                die("Not a git repository");

        if (load_config() == ERR)
                die("Failed to load repo config.");

        for (i = 0; i < ARRAY_SIZE(views) && (view = &views[i]); i++)
                view->cmd_env = getenv(view->cmd_env);

        request = opt_request;

        init_display();

        while (view_driver(display[current_view], request)) {
                int key;
                int i;

                foreach_view (view, i)
                        update_view(view);

                /* Refresh, accept single keystroke of input */
                key = wgetch(status_win);
                request = get_request(key);

                /* Some low-level request handling. This keeps access to
                 * status_win restricted. */
                switch (request) {
                case REQ_PROMPT:
                        report(":");
                        /* Temporarily switch to line-oriented and echoed
                         * input. */
                        nocbreak();
                        echo();

                        if (wgetnstr(status_win, opt_cmd + 4, sizeof(opt_cmd) - 4) == OK) {
                                memcpy(opt_cmd, "git ", 4);
                                opt_request = REQ_VIEW_PAGER;
                        } else {
                                request = ERR;
                        }

                        noecho();
                        cbreak();
                        break;

                case REQ_SCREEN_RESIZE:
                {
                        int height, width;

                        getmaxyx(stdscr, height, width);

                        /* Resize the status view and let the view driver take
                         * care of resizing the displayed views. */
                        wresize(status_win, 1, width);
                        mvwin(status_win, height - 1, 0);
                        wrefresh(status_win);
                        break;
                }
                default:
                        break;
                }
        }

        quit(0);

        return 0;
}

/**
 * [[refspec]]
 * Revision specification
 * ----------------------
 * This section describes various ways to specify what revisions to display
 * or otherwise limit the view to. tig(1) does not itself parse the described
 * revision options so refer to the relevant git man pages for futher
 * information. Relevant man pages besides git-log(1) are git-diff(1) and
 * git-rev-list(1).
 *
 * You can tune the interaction with git by making use of the options
 * explained in this section. For example, by configuring the environment
 * variables described in the  <<view-commands, "View commands">> section.
 *
 * Limit by path name
 * ~~~~~~~~~~~~~~~~~~
 * If you are interested only in those revisions that made changes to a
 * specific file (or even several files) list the files like this:
 *
 *      $ tig log Makefile README
 *
 * To avoid ambiguity with repository references such as tag name, be sure
 * to separate file names from other git options using "\--". So if you
 * have a file named 'master' it will clash with the reference named
 * 'master', and thus you will have to use:
 *
 *      $ tig log -- master
 *
 * NOTE: For the main view, avoiding ambiguity will in some cases require
 * you to specify two "\--" options. The first will make tig(1) stop
 * option processing and the latter will be passed to git log.
 *
 * Limit by date or number
 * ~~~~~~~~~~~~~~~~~~~~~~~
 * To speed up interaction with git, you can limit the amount of commits
 * to show both for the log and main view. Either limit by date using
 * e.g. `--since=1.month` or limit by the number of commits using `-n400`.
 *
 * If you are only interested in changed that happened between two dates
 * you can use:
 *
 *      $ tig -- --after="May 5th" --before="2006-05-16 15:44"
 *
 * NOTE: If you want to avoid having to quote dates containing spaces you
 * can use "." instead, e.g. `--after=May.5th`.
 *
 * Limiting by commit ranges
 * ~~~~~~~~~~~~~~~~~~~~~~~~~
 * Alternatively, commits can be limited to a specific range, such as
 * "all commits between 'tag-1.0' and 'tag-2.0'". For example:
 *
 *      $ tig log tag-1.0..tag-2.0
 *
 * This way of commit limiting makes it trivial to only browse the commits
 * which haven't been pushed to a remote branch. Assuming 'origin' is your
 * upstream remote branch, using:
 *
 *      $ tig log origin..HEAD
 *
 * will list what will be pushed to the remote branch. Optionally, the ending
 * 'HEAD' can be left out since it is implied.
 *
 * Limiting by reachability
 * ~~~~~~~~~~~~~~~~~~~~~~~~
 * Git interprets the range specifier "tag-1.0..tag-2.0" as
 * "all commits reachable from 'tag-2.0' but not from 'tag-1.0'".
 * Where reachability refers to what commits are ancestors (or part of the
 * history) of the branch or tagged revision in question.
 *
 * If you prefer to specify which commit to preview in this way use the
 * following:
 *
 *      $ tig log tag-2.0 ^tag-1.0
 *
 * You can think of '^' as a negation operator. Using this alternate syntax,
 * it is possible to further prune commits by specifying multiple branch
 * cut offs.
 *
 * Combining revisions specification
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 * Revisions options can to some degree be combined, which makes it possible
 * to say "show at most 20 commits from within the last month that changed
 * files under the Documentation/ directory."
 *
 *      $ tig -- --since=1.month -n20 -- Documentation/
 *
 * Examining all repository references
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 * In some cases, it can be useful to query changes across all references
 * in a repository. An example is to ask "did any line of development in
 * this repository change a particular file within the last week". This
 * can be accomplished using:
 *
 *      $ tig -- --all --since=1.week -- Makefile
 *
 * BUGS
 * ----
 * Known bugs and problems:
 *
 * - In it's current state tig is pretty much UTF-8 only.
 *
 * - If the screen width is very small the main view can draw
 *   outside the current view causing bad wrapping. Same goes
 *   for title and status windows.
 *
 * - The cursor can wrap-around on the last line and cause the
 *   window to scroll.
 *
 * TODO
 * ----
 * Features that should be explored.
 *
 * - Searching.
 *
 * - Locale support.
 *
 * COPYRIGHT
 * ---------
 * Copyright (c) 2006 Jonas Fonseca <fonseca@diku.dk>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * SEE ALSO
 * --------
 * - link:http://www.kernel.org/pub/software/scm/git/docs/[git(7)],
 * - link:http://www.kernel.org/pub/software/scm/cogito/docs/[cogito(7)]
 *
 * Other git repository browsers:
*
 *  - gitk(1)
 *  - qgit(1)
 *  - gitview(1)
 **/