[filter-repo PATCH] filter-repo: add new --replace-message option

[Gwyneth Morgan <gwymor@tilde.club>]

Like --replace-text, add an option --replace-message which replaces text
in commit message bodies, so that users can easily replace text without
constructing a --message-callback.
---
 Documentation/git-filter-repo.txt | 19 +++++++-
 git-filter-repo                   | 12 ++++-
 t/t9390-filter-repo.sh            |  1 +
 t/t9390/basic-message             | 78 +++++++++++++++++++++++++++++++
 t/t9390/sample-message            |  2 +
 5 files changed, 110 insertions(+), 2 deletions(-)
 create mode 100644 t/t9390/basic-message
 create mode 100644 t/t9390/sample-message

diff --git a/Documentation/git-filter-repo.txt b/Documentation/git-filter-repo.txt
index 2798378..7a71375 100644
--- a/Documentation/git-filter-repo.txt
+++ b/Documentation/git-filter-repo.txt
@@ -181,6 +181,10 @@ Renaming of refs (see also --refname-callback)
 Filtering of commit messages (see also --message-callback)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+--replace-message <expressions_file>::
+	A file with expressions that, if found in commit messages, will
+	be replaced. This file uses the same syntax as --replace-text.
+
 --preserve-commit-hashes::
 	By default, since commits are rewritten and thus gain new
 	hashes, references to old commit hashes in commit messages are
@@ -894,7 +898,20 @@ YYYY-MM-DD.  In the expressions file, there are a few things to note:
     beginning and ends of lines rather than the beginning and end of file.
     See https://docs.python.org/3/library/re.html for details.
 
-See also the `--blob-callback` from <<CALLBACKS>>.
+See also the `--blob-callback` from <<CALLBACKS>>.  Similarly, if you
+want to modify commit messages, you can do so with the same syntax.  For
+example, with a file named expressions.txt containing
+
+--------------------------------------------------
+foo==>bar
+--------------------------------------------------
+
+then running
+--------------------------------------------------
+git filter-repo --replace-message expressions.txt
+--------------------------------------------------
+
+will replace `foo` in commit messages with `bar`.
 
 Refname based filtering
 ~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/git-filter-repo b/git-filter-repo
index b91bd96..5fe0f91 100755
--- a/git-filter-repo
+++ b/git-filter-repo
@@ -1843,6 +1843,10 @@ EXAMPLES
 
     messages = parser.add_argument_group(title=_("Filtering of commit messages "
                                                "(see also --message-callback)"))
+    messages.add_argument('--replace-message', metavar='EXPRESSIONS_FILE',
+        help=_("A file with expressions that, if found in commit messages, "
+               "will be replaced. This file uses the same syntax as "
+               "--replace-text."))
     messages.add_argument('--preserve-commit-hashes', action='store_true',
         help=_("By default, since commits are rewritten and thus gain new "
                "hashes, references to old commit hashes in commit messages "
@@ -2189,6 +2193,8 @@ EXAMPLES
       args.mailmap = MailmapInfo(args.mailmap)
     if args.replace_text:
       args.replace_text = FilteringOptions.get_replace_text(args.replace_text)
+    if args.replace_message:
+      args.replace_message = FilteringOptions.get_replace_text(args.replace_message)
     if args.strip_blobs_with_ids:
       with open(args.strip_blobs_with_ids, 'br') as f:
         args.strip_blobs_with_ids = set(f.read().split())
@@ -3374,9 +3380,13 @@ class RepoFilter(object):
     if not self._args.preserve_commit_hashes:
       commit.message = self._hash_re.sub(self._translate_commit_hash,
                                          commit.message)
+    if self._args.replace_message:
+      for literal, replacement in self._args.replace_message['literals']:
+        commit.message = commit.message.replace(literal, replacement)
+      for regex,   replacement in self._args.replace_message['regexes']:
+        commit.message = regex.sub(replacement, commit.message)
     if self._message_callback:
       commit.message = self._message_callback(commit.message)
-
     # Change the author & committer according to mailmap rules
     args = self._args
     if args.mailmap:
diff --git a/t/t9390-filter-repo.sh b/t/t9390-filter-repo.sh
index 3f567e7..6d2d985 100755
--- a/t/t9390-filter-repo.sh
+++ b/t/t9390-filter-repo.sh
@@ -39,6 +39,7 @@ filter_testcase basic basic-filename --invert-paths --path-glob 't*en*'
 filter_testcase basic basic-numbers  --invert-paths --path-regex 'f.*e.*e'
 filter_testcase basic basic-mailmap  --mailmap ../t9390/sample-mailmap
 filter_testcase basic basic-replace  --replace-text ../t9390/sample-replace
+filter_testcase basic basic-message  --replace-message ../t9390/sample-message
 filter_testcase empty empty-keepme   --path keepme
 filter_testcase empty more-empty-keepme --path keepme --prune-empty=always \
 		                                   --prune-degenerate=always
diff --git a/t/t9390/basic-message b/t/t9390/basic-message
new file mode 100644
index 0000000..4ac1968
--- /dev/null
+++ b/t/t9390/basic-message
@@ -0,0 +1,78 @@
+feature done
+blob
+mark :1
+data 8
+initial
+
+reset refs/heads/B
+commit refs/heads/B
+mark :2
+author Little O. Me <me@little.net> 1535228562 -0700
+committer Little O. Me <me@little.net> 1535228562 -0700
+data 9
+Modified
+M 100644 :1 filename
+M 100644 :1 ten
+M 100644 :1 twenty
+
+blob
+mark :3
+data 11
+twenty-mod
+
+commit refs/heads/B
+mark :4
+author Little 'ol Me <me@laptop.(none)> 1535229544 -0700
+committer Little 'ol Me <me@laptop.(none)> 1535229544 -0700
+data 18
+add the number 20
+from :2
+M 100644 :3 twenty
+
+blob
+mark :5
+data 8
+ten-mod
+
+commit refs/heads/A
+mark :6
+author Little O. Me <me@machine52.little.net> 1535229523 -0700
+committer Little O. Me <me@machine52.little.net> 1535229523 -0700
+data 8
+add ten
+from :2
+M 100644 :5 ten
+
+commit refs/heads/master
+mark :7
+author Lit.e Me <me@fire.com> 1535229559 -0700
+committer Lit.e Me <me@fire.com> 1535229580 -0700
+data 24
+Merge branch 'A' into B
+from :4
+merge :6
+M 100644 :5 ten
+
+blob
+mark :8
+data 6
+final
+
+commit refs/heads/master
+mark :9
+author Little Me <me@bigcompany.com> 1535229601 -0700
+committer Little Me <me@bigcompany.com> 1535229601 -0700
+data 9
+whatever
+from :7
+M 100644 :8 filename
+M 100644 :8 ten
+M 100644 :8 twenty
+
+tag v1.0
+from :9
+tagger Little John <second@merry.men> 1535229618 -0700
+data 5
+v1.0
+
+done
diff --git a/t/t9390/sample-message b/t/t9390/sample-message
new file mode 100644
index 0000000..a374d61
--- /dev/null
+++ b/t/t9390/sample-message
@@ -0,0 +1,2 @@
+Initial==>Modified
+regex:tw.nty==>the number 20
-- 
2.32.0