Handle branch names with slashes

Teach stgit to handle branch names with slashes in them; that is,
branches living in a subdirectory of .git/refs/heads.

I had to change the patch@branch/top command-line syntax to
patch@branch//top, in order to get sane parsing. The /top variant is
still available for repositories that have no slashy branches; it is
disabled as soon as there exists at least one subdirectory of
refs/heads. Preferably, this compatibility hack can be killed some
time in the future.

Signed-off-by: Karl Hasselström <kha@treskal.com>

diff --git a/stgit/commands/branch.py b/stgit/commands/branch.py
index 2218bbb..d348409 100644 (file)
--- a/stgit/commands/branch.py
+++ b/stgit/commands/branch.py
@@ -172,7 +172,10 @@ def func(parser, options, args):
         if len(args) != 0:
             parser.error('incorrect number of arguments')
 
         if len(args) != 0:
             parser.error('incorrect number of arguments')
 

-        branches = os.listdir(os.path.join(basedir.get(), 'refs', 'heads'))
+        branches = []
+        basepath = os.path.join(basedir.get(), 'refs', 'heads')
+        for path, files, dirs in walk_tree(basepath):
+            branches += [os.path.join(path, f) for f in files]

         branches.sort()
 
         if branches:
         branches.sort()
 
         if branches:

diff --git a/stgit/commands/common.py b/stgit/commands/common.py
index c6ca514..9b97eb6 100644 (file)
--- a/stgit/commands/common.py
+++ b/stgit/commands/common.py
@@ -18,7 +18,7 @@ along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 """
 
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 """
 

-import sys, os, re
+import sys, os, os.path, re

 from optparse import OptionParser, make_option
 
 from stgit.utils import *
 from optparse import OptionParser, make_option
 
 from stgit.utils import *


@@ -34,54 +34,74 @@ class CmdException(Exception):
 
 
 # Utility functions
 
 
 # Utility functions

+class RevParseException(Exception):
+    """Revision spec parse error."""
+    pass
+
+def parse_rev(rev):
+    """Parse a revision specification into its
+    patchname@branchname//patch_id parts. If no branch name has a slash
+    in it, also accept / instead of //."""
+    files, dirs = list_files_and_dirs(os.path.join(basedir.get(),
+                                                   'refs', 'heads'))
+    if len(dirs) != 0:
+        # We have branch names with / in them.
+        branch_chars = r'[^@]'
+        patch_id_mark = r'//'
+    else:
+        # No / in branch names.
+        branch_chars = r'[^@/]'
+        patch_id_mark = r'(/|//)'
+    patch_re = r'(?P<patch>[^@/]+)'
+    branch_re = r'@(?P<branch>%s+)' % branch_chars
+    patch_id_re = r'%s(?P<patch_id>[a-z.]*)' % patch_id_mark
+
+    # Try //patch_id.
+    m = re.match(r'^%s$' % patch_id_re, rev)
+    if m:
+        return None, None, m.group('patch_id')
+
+    # Try path[@branch]//patch_id.
+    m = re.match(r'^%s(%s)?%s$' % (patch_re, branch_re, patch_id_re), rev)
+    if m:
+        return m.group('patch'), m.group('branch'), m.group('patch_id')
+
+    # Try patch[@branch].
+    m = re.match(r'^%s(%s)?$' % (patch_re, branch_re), rev)
+    if m:
+        return m.group('patch'), m.group('branch'), None
+
+    # No, we can't parse that.
+    raise RevParseException
+

 def git_id(rev):
     """Return the GIT id
     """
     if not rev:
         return None
 def git_id(rev):
     """Return the GIT id
     """
     if not rev:
         return None

-    
-    rev_list = rev.split('/')
-    if len(rev_list) == 2:
-        patch_id = rev_list[1]
-        if not patch_id:
-            patch_id = 'top'
-    elif len(rev_list) == 1:
-        patch_id = 'top'
-    else:
-        patch_id = None
-
-    patch_branch = rev_list[0].split('@')
-    if len(patch_branch) == 1:
-        series = crt_series
-    elif len(patch_branch) == 2:
-        series = stack.Series(patch_branch[1])
-    else:
-        raise CmdException, 'Unknown id: %s' % rev
-
-    patch_name = patch_branch[0]
-    if not patch_name:
-        patch_name = series.get_current()
-        if not patch_name:
-            raise CmdException, 'No patches applied'
-
-    # patch
-    if patch_name in series.get_applied() \
-           or patch_name in series.get_unapplied():
-        if patch_id == 'top':
-            return series.get_patch(patch_name).get_top()
-        elif patch_id == 'bottom':
-            return series.get_patch(patch_name).get_bottom()
-        # Note we can return None here.
-        elif patch_id == 'top.old':
-            return series.get_patch(patch_name).get_old_top()
-        elif patch_id == 'bottom.old':
-            return series.get_patch(patch_name).get_old_bottom()
-
-    # base
-    if patch_name == 'base' and len(rev_list) == 1:
-        return read_string(series.get_base_file())
-
-    # anything else failed
+    try:
+        patch, branch, patch_id = parse_rev(rev)
+        if branch == None:
+            series = crt_series
+        else:
+            series = stack.Series(branch)
+        if patch == None:
+            patch = series.get_current()
+            if not patch:
+                raise CmdException, 'No patches applied'
+        if patch in series.get_applied() or patch in series.get_unapplied():
+            if patch_id in ['top', '', None]:
+                return series.get_patch(patch).get_top()
+            elif patch_id == 'bottom':
+                return series.get_patch(patch).get_bottom()
+            elif patch_id == 'top.old':
+                return series.get_patch(patch).get_old_top()
+            elif patch_id == 'bottom.old':
+                return series.get_patch(patch).get_old_bottom()
+        if patch == 'base' and patch_id == None:
+            return read_string(series.get_base_file())
+    except RevParseException:
+        pass

     return git.rev_parse(rev + '^{commit}')
 
 def check_local_changes():
     return git.rev_parse(rev + '^{commit}')
 
 def check_local_changes():

diff --git a/stgit/commands/diff.py b/stgit/commands/diff.py
index 7dc6c5d..d765784 100644 (file)
--- a/stgit/commands/diff.py
+++ b/stgit/commands/diff.py
@@ -33,12 +33,12 @@ or a tree-ish object and another tree-ish object. File names can also
 be given to restrict the diff output. The tree-ish object can be a
 standard git commit, tag or tree. In addition to these, the command
 also supports 'base', representing the bottom of the current stack,
 be given to restrict the diff output. The tree-ish object can be a
 standard git commit, tag or tree. In addition to these, the command
 also supports 'base', representing the bottom of the current stack,

-and '[patch]/[bottom | top]' for the patch boundaries (defaulting to
+and '[patch][//[bottom | top]]' for the patch boundaries (defaulting to

 the current one):
 
 the current one):
 

-rev = '([patch]/[bottom | top]) | <tree-ish> | base'
+rev = '([patch][//[bottom | top]]) | <tree-ish> | base'

 
 

-If neither bottom or top are given but a '/' is present, the command
+If neither bottom nor top are given but a '//' is present, the command

 shows the specified patch (defaulting to the current one)."""
 
 options = [make_option('-r', metavar = 'rev1[:[rev2]]', dest = 'revs',
 shows the specified patch (defaulting to the current one)."""
 
 options = [make_option('-r', metavar = 'rev1[:[rev2]]', dest = 'revs',


@@ -55,10 +55,14 @@ def func(parser, options, args):
         rev_list = options.revs.split(':')
         rev_list_len = len(rev_list)
         if rev_list_len == 1:
         rev_list = options.revs.split(':')
         rev_list_len = len(rev_list)
         if rev_list_len == 1:

-            if rev_list[0][-1] == '/':
+            rev = rev_list[0]
+            if rev[-1] == '/':

                 # the whole patch
                 # the whole patch

-                rev1 = rev_list[0] + 'bottom'
-                rev2 = rev_list[0] + 'top'
+                rev = rev[:-1]
+                if rev[-1] == '/':
+                    rev = rev[:-1]
+                rev1 = rev + '//bottom'
+                rev2 = rev + '//top'

             else:
                 rev1 = rev_list[0]
                 rev2 = None
             else:
                 rev1 = rev_list[0]
                 rev2 = None

diff --git a/stgit/commands/files.py b/stgit/commands/files.py
index 0694d83..b33bd2a 100644 (file)
--- a/stgit/commands/files.py
+++ b/stgit/commands/files.py
@@ -53,8 +53,8 @@ def func(parser, options, args):
     else:
         parser.error('incorrect number of arguments')
 
     else:
         parser.error('incorrect number of arguments')
 

-    rev1 = git_id('%s/bottom' % patch)
-    rev2 = git_id('%s/top' % patch)
+    rev1 = git_id('%s//bottom' % patch)
+    rev2 = git_id('%s//top' % patch)

 
     if options.stat:
         print git.diffstat(rev1 = rev1, rev2 = rev2)
 
     if options.stat:
         print git.diffstat(rev1 = rev1, rev2 = rev2)

diff --git a/stgit/commands/id.py b/stgit/commands/id.py
index 1cf6ea6..284589a 100644 (file)
--- a/stgit/commands/id.py
+++ b/stgit/commands/id.py
@@ -28,7 +28,7 @@ usage = """%prog [options] [id]
 
 Print the hash value of a GIT id (defaulting to HEAD). In addition to
 the standard GIT id's like heads and tags, this command also accepts
 
 Print the hash value of a GIT id (defaulting to HEAD). In addition to
 the standard GIT id's like heads and tags, this command also accepts

-'base[@<branch>]' and '[<patch>[@<branch>]][/(bottom | top)]'. If no
+'base[@<branch>]' and '[<patch>[@<branch>]][//[bottom | top]]'. If no

 'top' or 'bottom' are passed and <patch> is a valid patch name, 'top'
 will be used by default."""
 
 'top' or 'bottom' are passed and <patch> is a valid patch name, 'top'
 will be used by default."""
 

diff --git a/stgit/commands/mail.py b/stgit/commands/mail.py
index 5e01ea1..3928b81 100644 (file)
--- a/stgit/commands/mail.py
+++ b/stgit/commands/mail.py
@@ -324,10 +324,10 @@ def __build_message(tmpl, patch, patch_nr, total_nr, msg_id, ref_id, options):
                  'shortdescr':   short_descr,
                  'longdescr':    long_descr,
                  'endofheaders': headers_end,
                  'shortdescr':   short_descr,
                  'longdescr':    long_descr,
                  'endofheaders': headers_end,

-                 'diff':         git.diff(rev1 = git_id('%s/bottom' % patch),
-                                          rev2 = git_id('%s/top' % patch)),
-                 'diffstat':     git.diffstat(rev1 = git_id('%s/bottom'%patch),
-                                              rev2 = git_id('%s/top' % patch)),
+                 'diff':         git.diff(rev1 = git_id('%s//bottom' % patch),
+                                          rev2 = git_id('%s//top' % patch)),
+                 'diffstat':     git.diffstat(rev1 = git_id('%s//bottom'%patch),
+                                              rev2 = git_id('%s//top' % patch)),

                  'date':         email.Utils.formatdate(localtime = True),
                  'version':      version_str,
                  'patchnr':      patch_nr_str,
                  'date':         email.Utils.formatdate(localtime = True),
                  'version':      version_str,
                  'patchnr':      patch_nr_str,

diff --git a/stgit/git.py b/stgit/git.py
index 2884f36..716609c 100644 (file)
--- a/stgit/git.py
+++ b/stgit/git.py
@@ -225,7 +225,8 @@ def get_head():
 def get_head_file():
     """Returns the name of the file pointed to by the HEAD link
     """
 def get_head_file():
     """Returns the name of the file pointed to by the HEAD link
     """

-    return os.path.basename(_output_one_line('git-symbolic-ref HEAD'))
+    return strip_prefix('refs/heads/',
+                        _output_one_line('git-symbolic-ref HEAD'))

 
 def set_head_file(ref):
     """Resets HEAD to point to a new ref
 
 def set_head_file(ref):
     """Resets HEAD to point to a new ref


@@ -233,7 +234,8 @@ def set_head_file(ref):
     # head cache flushing is needed since we might have a different value
     # in the new head
     __clear_head_cache()
     # head cache flushing is needed since we might have a different value
     # in the new head
     __clear_head_cache()

-    if __run('git-symbolic-ref HEAD', [ref]) != 0:
+    if __run('git-symbolic-ref HEAD',
+             [os.path.join('refs', 'heads', ref)]) != 0:

         raise GitException, 'Could not set head to "%s"' % ref
 
 def __set_head(val):
         raise GitException, 'Could not set head to "%s"' % ref
 
 def __set_head(val):


@@ -272,6 +274,7 @@ def rev_parse(git_id):
 def branch_exists(branch):
     """Existence check for the named branch
     """
 def branch_exists(branch):
     """Existence check for the named branch
     """

+    branch = os.path.join('refs', 'heads', branch)

     for line in _output_lines('git-rev-parse --symbolic --all 2>&1'):
         if line.strip() == branch:
             return True
     for line in _output_lines('git-rev-parse --symbolic --all 2>&1'):
         if line.strip() == branch:
             return True


@@ -282,12 +285,11 @@ def branch_exists(branch):
 def create_branch(new_branch, tree_id = None):
     """Create a new branch in the git repository
     """
 def create_branch(new_branch, tree_id = None):
     """Create a new branch in the git repository
     """

-    new_head = os.path.join('refs', 'heads', new_branch)
-    if branch_exists(new_head):
+    if branch_exists(new_branch):

         raise GitException, 'Branch "%s" already exists' % new_branch
 
     current_head = get_head()
         raise GitException, 'Branch "%s" already exists' % new_branch
 
     current_head = get_head()

-    set_head_file(new_head)
+    set_head_file(new_branch)

     __set_head(current_head)
 
     # a checkout isn't needed if new branch points to the current head
     __set_head(current_head)
 
     # a checkout isn't needed if new branch points to the current head


@@ -297,22 +299,22 @@ def create_branch(new_branch, tree_id = None):
     if os.path.isfile(os.path.join(basedir.get(), 'MERGE_HEAD')):
         os.remove(os.path.join(basedir.get(), 'MERGE_HEAD'))
 
     if os.path.isfile(os.path.join(basedir.get(), 'MERGE_HEAD')):
         os.remove(os.path.join(basedir.get(), 'MERGE_HEAD'))
 

-def switch_branch(name):
+def switch_branch(new_branch):

     """Switch to a git branch
     """
     global __head
 
     """Switch to a git branch
     """
     global __head
 

-    new_head = os.path.join('refs', 'heads', name)
-    if not branch_exists(new_head):
-        raise GitException, 'Branch "%s" does not exist' % name
+    if not branch_exists(new_branch):
+        raise GitException, 'Branch "%s" does not exist' % new_branch

 
 

-    tree_id = rev_parse(new_head + '^{commit}')
+    tree_id = rev_parse(os.path.join('refs', 'heads', new_branch)
+                        + '^{commit}')

     if tree_id != get_head():
         refresh_index()
         if __run('git-read-tree -u -m', [get_head(), tree_id]) != 0:
             raise GitException, 'git-read-tree failed (local changes maybe?)'
         __head = tree_id
     if tree_id != get_head():
         refresh_index()
         if __run('git-read-tree -u -m', [get_head(), tree_id]) != 0:
             raise GitException, 'git-read-tree failed (local changes maybe?)'
         __head = tree_id

-    set_head_file(new_head)
+    set_head_file(new_branch)

 
     if os.path.isfile(os.path.join(basedir.get(), 'MERGE_HEAD')):
         os.remove(os.path.join(basedir.get(), 'MERGE_HEAD'))
 
     if os.path.isfile(os.path.join(basedir.get(), 'MERGE_HEAD')):
         os.remove(os.path.join(basedir.get(), 'MERGE_HEAD'))


@@ -320,25 +322,23 @@ def switch_branch(name):
 def delete_branch(name):
     """Delete a git branch
     """
 def delete_branch(name):
     """Delete a git branch
     """

-    branch_head = os.path.join('refs', 'heads', name)
-    if not branch_exists(branch_head):
+    if not branch_exists(name):

         raise GitException, 'Branch "%s" does not exist' % name
         raise GitException, 'Branch "%s" does not exist' % name

-    os.remove(os.path.join(basedir.get(), branch_head))
+    remove_file_and_dirs(os.path.join(basedir.get(), 'refs', 'heads'),
+                         name)

 
 def rename_branch(from_name, to_name):
     """Rename a git branch
     """
 
 def rename_branch(from_name, to_name):
     """Rename a git branch
     """

-    from_head = os.path.join('refs', 'heads', from_name)
-    if not branch_exists(from_head):
+    if not branch_exists(from_name):

         raise GitException, 'Branch "%s" does not exist' % from_name
         raise GitException, 'Branch "%s" does not exist' % from_name

-    to_head = os.path.join('refs', 'heads', to_name)
-    if branch_exists(to_head):
+    if branch_exists(to_name):

         raise GitException, 'Branch "%s" already exists' % to_name
 
     if get_head_file() == from_name:
         raise GitException, 'Branch "%s" already exists' % to_name
 
     if get_head_file() == from_name:

-        set_head_file(to_head)
-    os.rename(os.path.join(basedir.get(), from_head), \
-              os.path.join(basedir.get(), to_head))
+        set_head_file(to_name)
+    rename(os.path.join(basedir.get(), 'refs', 'heads'),
+           from_name, to_name)

 
 def add(names):
     """Add the files or recursively add the directory contents
 
 def add(names):
     """Add the files or recursively add the directory contents

diff --git a/stgit/stack.py b/stgit/stack.py
index f83161b..49b50e7 100644 (file)
--- a/stgit/stack.py
+++ b/stgit/stack.py
@@ -443,8 +443,7 @@ class Series:
 
         os.makedirs(self.__patch_dir)
 
 
         os.makedirs(self.__patch_dir)
 

-        if not os.path.isdir(bases_dir):
-            os.makedirs(bases_dir)
+        create_dirs(bases_dir)

 
         create_empty_file(self.__applied_file)
         create_empty_file(self.__unapplied_file)
 
         create_empty_file(self.__applied_file)
         create_empty_file(self.__unapplied_file)


@@ -502,11 +501,14 @@ class Series:
         git.rename_branch(self.__name, to_name)
 
         if os.path.isdir(self.__series_dir):
         git.rename_branch(self.__name, to_name)
 
         if os.path.isdir(self.__series_dir):

-            os.rename(self.__series_dir, to_stack.__series_dir)
+            rename(os.path.join(self.__base_dir, 'patches'),
+                   self.__name, to_stack.__name)

         if os.path.exists(self.__base_file):
         if os.path.exists(self.__base_file):

-            os.rename(self.__base_file, to_stack.__base_file)
+            rename(os.path.join(self.__base_dir, 'refs', 'bases'),
+                   self.__name, to_stack.__name)

         if os.path.exists(self.__refs_dir):
         if os.path.exists(self.__refs_dir):

-            os.rename(self.__refs_dir, to_stack.__refs_dir)
+            rename(os.path.join(self.__base_dir, 'refs', 'patches'),
+                   self.__name, to_stack.__name)

 
         self.__init__(to_name)
 
 
         self.__init__(to_name)
 


@@ -560,16 +562,19 @@ class Series:
             else:
                 print 'Patch directory %s is not empty.' % self.__name
             if not os.listdir(self.__series_dir):
             else:
                 print 'Patch directory %s is not empty.' % self.__name
             if not os.listdir(self.__series_dir):

-                os.rmdir(self.__series_dir)
+                remove_dirs(os.path.join(self.__base_dir, 'patches'),
+                            self.__name)

             else:
                 print 'Series directory %s is not empty.' % self.__name
             if not os.listdir(self.__refs_dir):
             else:
                 print 'Series directory %s is not empty.' % self.__name
             if not os.listdir(self.__refs_dir):

-                os.rmdir(self.__refs_dir)
+                remove_dirs(os.path.join(self.__base_dir, 'refs', 'patches'),
+                            self.__name)

             else:
                 print 'Refs directory %s is not empty.' % self.__refs_dir
 
         if os.path.exists(self.__base_file):
             else:
                 print 'Refs directory %s is not empty.' % self.__refs_dir
 
         if os.path.exists(self.__base_file):

-            os.remove(self.__base_file)
+            remove_file_and_dirs(
+                os.path.join(self.__base_dir, 'refs', 'bases'), self.__name)

 
     def refresh_patch(self, files = None, message = None, edit = False,
                       show_patch = False,
 
     def refresh_patch(self, files = None, message = None, edit = False,
                       show_patch = False,

diff --git a/stgit/utils.py b/stgit/utils.py
index 5749b3b..68b8f58 100644 (file)
--- a/stgit/utils.py
+++ b/stgit/utils.py
@@ -1,6 +1,8 @@
 """Common utility functions
 """
 
 """Common utility functions
 """
 

+import errno, os, os.path
+

 __copyright__ = """
 Copyright (C) 2005, Catalin Marinas <catalin.marinas@gmail.com>
 
 __copyright__ = """
 Copyright (C) 2005, Catalin Marinas <catalin.marinas@gmail.com>
 


@@ -18,6 +20,12 @@ along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 """
 
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 """
 

+def mkdir_file(filename, mode):
+    """Opens filename with the given mode, creating the directory it's
+    in if it doesn't already exist."""
+    create_dirs(os.path.dirname(filename))
+    return file(filename, mode)
+

 def read_string(filename, multiline = False):
     """Reads the first line from a file
     """
 def read_string(filename, multiline = False):
     """Reads the first line from a file
     """


@@ -32,7 +40,7 @@ def read_string(filename, multiline = False):
 def write_string(filename, line, multiline = False):
     """Writes 'line' to file and truncates it
     """
 def write_string(filename, line, multiline = False):
     """Writes 'line' to file and truncates it
     """

-    f = file(filename, 'w+')
+    f = mkdir_file(filename, 'w+')

     if multiline:
         f.write(line)
     else:
     if multiline:
         f.write(line)
     else:


@@ -42,7 +50,7 @@ def write_string(filename, line, multiline = False):
 def append_strings(filename, lines):
     """Appends 'lines' sequence to file
     """
 def append_strings(filename, lines):
     """Appends 'lines' sequence to file
     """

-    f = file(filename, 'a+')
+    f = mkdir_file(filename, 'a+')

     for line in lines:
         print >> f, line
     f.close()
     for line in lines:
         print >> f, line
     f.close()


@@ -50,14 +58,14 @@ def append_strings(filename, lines):
 def append_string(filename, line):
     """Appends 'line' to file
     """
 def append_string(filename, line):
     """Appends 'line' to file
     """

-    f = file(filename, 'a+')
+    f = mkdir_file(filename, 'a+')

     print >> f, line
     f.close()
 
 def insert_string(filename, line):
     """Inserts 'line' at the beginning of the file
     """
     print >> f, line
     f.close()
 
 def insert_string(filename, line):
     """Inserts 'line' at the beginning of the file
     """

-    f = file(filename, 'r+')
+    f = mkdir_file(filename, 'r+')

     lines = f.readlines()
     f.seek(0); f.truncate()
     print >> f, line
     lines = f.readlines()
     f.seek(0); f.truncate()
     print >> f, line


@@ -67,4 +75,74 @@ def insert_string(filename, line):
 def create_empty_file(name):
     """Creates an empty file
     """
 def create_empty_file(name):
     """Creates an empty file
     """

-    file(name, 'w+').close()
+    mkdir_file(name, 'w+').close()
+
+def list_files_and_dirs(path):
+    """Return the sets of filenames and directory names in a
+    directory."""
+    files, dirs = [], []
+    for fd in os.listdir(path):
+        full_fd = os.path.join(path, fd)
+        if os.path.isfile(full_fd):
+            files.append(fd)
+        elif os.path.isdir(full_fd):
+            dirs.append(fd)
+    return files, dirs
+
+def walk_tree(basedir):
+    """Starting in the given directory, iterate through all its
+    subdirectories. For each subdirectory, yield the name of the
+    subdirectory (relative to the base directory), the list of
+    filenames in the subdirectory, and the list of directory names in
+    the subdirectory."""
+    subdirs = ['']
+    while subdirs:
+        subdir = subdirs.pop()
+        files, dirs = list_files_and_dirs(os.path.join(basedir, subdir))
+        for d in dirs:
+            subdirs.append(os.path.join(subdir, d))
+        yield subdir, files, dirs
+
+def strip_prefix(prefix, string):
+    """Return string, without the prefix. Blow up if string doesn't
+    start with prefix."""
+    assert string.startswith(prefix)
+    return string[len(prefix):]
+
+def remove_dirs(basedir, dirs):
+    """Starting at join(basedir, dirs), remove the directory if empty,
+    and try the same with its parent, until we find a nonempty
+    directory or reach basedir."""
+    path = dirs
+    while path:
+        try:
+            os.rmdir(os.path.join(basedir, path))
+        except OSError:
+            return # can't remove nonempty directory
+        path = os.path.dirname(path)
+
+def remove_file_and_dirs(basedir, file):
+    """Remove join(basedir, file), and then remove the directory it
+    was in if empty, and try the same with its parent, until we find a
+    nonempty directory or reach basedir."""
+    os.remove(os.path.join(basedir, file))
+    remove_dirs(basedir, os.path.dirname(file))
+
+def create_dirs(directory):
+    """Create the given directory, if the path doesn't already exist."""
+    if directory:
+        create_dirs(os.path.dirname(directory))
+        try:
+            os.mkdir(directory)
+        except OSError, e:
+            if e.errno != errno.EEXIST:
+                raise e
+
+def rename(basedir, file1, file2):
+    """Rename join(basedir, file1) to join(basedir, file2), not
+    leaving any empty directories behind and creating any directories
+    necessary."""
+    full_file2 = os.path.join(basedir, file2)
+    create_dirs(os.path.dirname(full_file2))
+    os.rename(os.path.join(basedir, file1), full_file2)
+    remove_dirs(basedir, os.path.dirname(file1))