commits-to-changelog script.

This script converts git commit messages to ChangeLog entries.  That
will hopefully allow us to forego adding ChangeLog entries in our
commits, which always leads to merge conflicts.

diff --git a/scripts/commits-to-changelog.py b/scripts/commits-to-changelog.py
new file mode 100755 (executable)
index 0000000..ef8ed09
--- /dev/null
+++ b/scripts/commits-to-changelog.py
@@ -0,0 +1,254 @@
+#!/usr/bin/python
+
+from optparse import OptionParser
+import subprocess
+import re
+import os.path
+import fnmatch
+import os
+
+# subtract 8 for the leading tabstop
+fill_column = 74 - 8
+
+path_to_root = None
+
+all_changelogs = {}
+
+def git (command, *args):
+    return subprocess.Popen (["git", command] + list (args), stdout = subprocess.PIPE).communicate () [0]
+
+def changelog_path (changelog):
+    global path_to_root
+    if not path_to_root:
+        path_to_root = git ("rev-parse", "--show-cdup").strip ()
+    (pathname, filename) = changelog
+    return path_to_root + "./" + pathname + "/" + filename
+
+def changelog_for_file (filename):
+    while filename != "":
+        dirname = os.path.dirname (filename)
+        if dirname in all_changelogs:
+            return (dirname, all_changelogs [dirname])
+        filename = dirname
+    assert False
+
+def changelogs_for_file_pattern (pattern, changed_files):
+    changelogs = set ()
+    for filename in changed_files:
+        suffix = filename
+        while suffix != "":
+            # FIXME: fnmatch doesn't support the {x,y} pattern
+            if fnmatch.fnmatch (suffix, pattern):
+                changelogs.add (changelog_for_file (filename))
+            (_, _, suffix) = suffix.partition ("/")
+    return changelogs
+
+def format_paragraph (paragraph):
+    lines = []
+    words = paragraph.split ()
+    current = words [0]
+    for word in words [1:]:
+        if len (current) + 1 + len (word) <= fill_column:
+            current += " " + word
+        else:
+            lines.append ("\t" + current)
+            current = word
+    lines.append ("\t" + current)
+    return lines
+
+def format_changelog_paragraph (files, paragraph):
+    files_string = ""
+    for (filename, entity) in files:
+        if len (files_string) > 0:
+            files_string += ", "
+        files_string += filename
+        if entity:
+            files_string += " (" + entity + ")"
+    return format_paragraph ("* " + files_string + ": " + paragraph)
+
+def append_paragraph (lines, paragraph):
+    if len (lines):
+        lines.append ("")
+    lines += paragraph
+
+def format_changelog_entries (commit, changed_files, prefix, file_entries):
+    changelogs = set ()
+    for f in changed_files:
+        changelogs.add (changelog_for_file (f))
+    marked_changelogs = set ()
+
+    author_line = git ("log", "-n1", "--date=short", "--format=%ad  %an  <%ae>", commit).strip ()
+
+    paragraphs = {}
+    for changelog in changelogs:
+        paragraphs [changelog] = [author_line]
+
+    for (files, comments) in file_entries:
+        changelog_entries = {}
+        for (filename, entity) in files:
+            entry_changelogs = changelogs_for_file_pattern (filename, changed_files)
+            if len (entry_changelogs) == 0:
+                print "Warning: could not match file %s in commit %s" % (filename, commit)
+            for changelog in entry_changelogs:
+                if changelog not in changelog_entries:
+                    changelog_entries [changelog] = []
+                changelog_entries [changelog].append ((filename, entity))
+                marked_changelogs.add (changelog)
+
+        for (changelog, files) in changelog_entries.items ():
+            append_paragraph (paragraphs [changelog], format_changelog_paragraph (files, comments [0]))
+            for paragraph in comments [1:]:
+                append_paragraph (paragraphs [changelog], format_paragraph (paragraph))
+
+    unmarked_changelogs = changelogs - marked_changelogs
+    for changelog in unmarked_changelogs:
+        if len (prefix) == 0:
+            print "Warning: empty entry in %s for commit %s" % (changelog_path (changelog), commit)
+            append_paragraph (paragraphs [changelog], format_paragraph ("FIXME: empty entry!"))
+        for paragraph in prefix:
+            append_paragraph (paragraphs [changelog], format_paragraph (paragraph))
+
+    return paragraphs
+
+def debug_print_commit (commit, raw_message, prefix, file_entries, changed_files, changelog_entries):
+    print "===================== Commit"
+    print commit
+    print "--------------------- RAW"
+    print raw_message
+    print "--------------------- Prefix"
+    for line in prefix:
+        print line
+    print "--------------------- File entries"
+    for (files, comments) in file_entries:
+        files_str = ""
+        for (filename, entity) in files:
+            if len (files_str):
+                files_str = files_str + ", "
+            files_str = files_str + filename
+            if entity:
+                files_str = files_str + " (" + entity + ")"
+        print files_str
+        for line in comments:
+            print "  " + line
+    print "--------------------- Files touched"
+    for f in changed_files:
+        print f
+    print "--------------------- ChangeLog entries"
+    for ((dirname, filename), lines) in changelog_entries.items ():
+        print "%s/%s:" % (dirname, filename)
+        for line in lines:
+            print line
+
+def process_commit (commit):
+    changed_files = map (lambda l: l.split () [2], git ("diff-tree", "--numstat", commit).splitlines () [1:])
+    if len (filter (lambda f: re.search ("(^|/)Change[Ll]og$", f), changed_files)):
+        return
+    raw_message = git ("log", "-n1", "--format=%B", commit)
+    # filter SVN migration message
+    message = re.sub ("(^|\n)svn path=[^\n]+revision=\d+(?=$|\n)", "", raw_message)
+    # filter ChangeLog headers
+    message = re.sub ("(^|\n)\d+-\d+-\d+[ \t]+((\w|[.-])+[ \t]+)+<[^\n>]+>(?=$|\n)", "", message)
+    # filter leading whitespace
+    message = re.sub ("^\s+", "", message)
+    # filter trailing whitespace
+    message = re.sub ("\s+$", "", message)
+    # paragraphize - first remove whitespace at beginnings and ends of lines
+    message = re.sub ("[ \t]*\n[ \t]*", "\n", message)
+    # paragraphize - now replace three or more consecutive newlines with two
+    message = re.sub ("\n\n\n+", "\n\n", message)
+    # paragraphize - replace single newlines with a space
+    message = re.sub ("(?<!\n)\n(?!\n)", " ", message)
+    # paragraphize - finally, replace double newlines with single ones
+    message = re.sub ("\n\n", "\n", message)
+
+    # A list of paragraphs (strings without newlines) that occur
+    # before the first file comments
+    prefix = []
+
+    # A list of tuples of the form ([(filename, entity), ...], [paragraph, ...]).
+    #
+    # Each describes a file comment, containing multiple paragraphs.
+    # Those paragraphs belong to a list of files, each with an
+    # optional entity (usually a function name).
+    file_entries = []
+
+    current_files = None
+    current_files_comments = None
+
+    for line in message.splitlines ():
+        if re.match ("\*\s[^:]+:", line):
+            if current_files:
+                file_entries.append ((current_files, current_files_comments))
+
+            (files, _, comments) = line.partition (":")
+
+            current_files_comments = [comments.strip ()]
+
+            current_files = []
+            for f in re.split ("\s*,\s*", files [1:].strip ()):
+                m = re.search ("\(([^()]+)\)$", f)
+                if m:
+                    filename = f [:m.start (0)].strip ()
+                    entity = m.group (1).strip ()
+                else:
+                    filename = f
+                    entity = None
+                current_files.append ((filename, entity))
+        else:
+            if current_files:
+                current_files_comments.append (line)
+            else:
+                prefix.append (line)
+    if current_files:
+        file_entries.append ((current_files, current_files_comments))
+
+    changelog_entries = format_changelog_entries (commit, changed_files, prefix, file_entries)
+
+    #debug_print_commit (commit, raw_message, prefix, file_entries, changed_files, changelog_entries)
+
+    return changelog_entries
+
+def start_changelog (changelog):
+    full_path = changelog_path (changelog)
+    old_name = full_path + ".old"
+    os.rename (full_path, old_name)
+    return open (full_path, "w")
+
+def finish_changelog (changelog, file):
+    old_file = open (changelog_path (changelog) + ".old")
+    file.write (old_file.read ())
+    old_file.close ()
+    file.close ()
+
+def append_lines (file, lines):
+    for line in lines:
+        file.write (line + "\n")
+    file.write ("\n")
+
+def main ():
+    usage = "usage: %prog [options] <start-commit>"
+    parser = OptionParser (usage)
+    (options, args) = parser.parse_args ()
+    if len (args) != 1:
+        parser.error ("incorrect number of arguments")
+    start_commit = args [0]
+
+    for filename in git ("ls-tree", "-r", "--name-only", "HEAD").splitlines ():
+        if re.search ("(^|/)Change[Ll]og$", filename):
+            (path, name) = os.path.split (filename)
+            all_changelogs [path] = name
+
+    commits = git ("rev-list", "--no-merges", "HEAD", "^%s" % start_commit).splitlines ()
+
+    touched_changelogs = {}
+    for commit in commits:
+        entries = process_commit (commit)
+        for (changelog, lines) in entries.items ():
+            if changelog not in touched_changelogs:
+                touched_changelogs [changelog] = start_changelog (changelog)
+            append_lines (touched_changelogs [changelog], lines)
+    for (changelog, file) in touched_changelogs.items ():
+        finish_changelog (changelog, file)
+
+if __name__ == "__main__":
+    main ()