FTFY: support wordwrapping commit messages

It's common for commit messages to be wrapped at odd places. git-gui
is often to blame. Adds support for automatically fixing up these
messages if running ftfy --amend, and adds a new option --msg-only for
fixing only the commit message.

Change-Id: Ia7ea529f8cb7395d34d9b39f1192598e9a1e315b

tools/wrap-commit-msg.py

@@ -0,0 +1,69 @@
+#!/usr/bin/env python
+##  Copyright (c) 2012 The WebM project authors. All Rights Reserved.
+##
+##  Use of this source code is governed by a BSD-style license
+##  that can be found in the LICENSE file in the root of the source
+##  tree. An additional intellectual property rights grant can be found
+##  in the file PATENTS.  All contributing project authors may
+##  be found in the AUTHORS file in the root of the source tree.
+##
+"""Wraps paragraphs of text, preserving manual formatting
+
+This is like fold(1), but has the special convention of not modifying lines
+that start with whitespace. This allows you to intersperse blocks with
+special formatting, like code blocks, with written prose. The prose will
+be wordwrapped, and the manual formatting will be preserved.
+
+ * This won't handle the case of a bulleted (or ordered) list specially, so
+   manual wrapping must be done.
+
+Occasionally it's useful to put something with explicit formatting that
+doesn't look at all like a block of text inline.
+
+  indicator = has_leading_whitespace(line);
+  if (indicator)
+    preserve_formatting(line);
+
+The intent is that this docstring would make it through the transform
+and still be legible and presented as it is in the source. If additional
+cases are handled, update this doc to describe the effect.
+"""
+
+__author__ = "jkoleszar@google.com"
+import textwrap
+import sys
+
+def wrap(text):
+    if text:
+        return textwrap.fill(text, break_long_words=False) + '\n'
+    return ""
+
+
+def main(fileobj):
+    text = ""
+    output = ""
+    while True:
+        line = fileobj.readline()
+        if not line:
+            break
+
+        if line.lstrip() == line:
+            text += line
+        else:
+            output += wrap(text)
+            text=""
+            output += line
+    output += wrap(text)
+
+    # Replace the file or write to stdout.
+    if fileobj == sys.stdin:
+        fileobj = sys.stdout
+    else:
+        fileobj.truncate(0)
+    fileobj.write(output)
+
+if __name__ == "__main__":
+    if len(sys.argv) > 1:
+        main(open(sys.argv[1], "r+"))
+    else:
+        main(sys.stdin)