[PATCH v3 0/4] rebase -i: avoid stale "# This is a combination of" in commit messages

Eric Sunshine pointed out that I had such a commit message in https://public-inbox.org/git/CAPig+cRrS0_nYJJY=O6cboV630sNQHPV5QGrQdD8MW-sYzNFGQ@mail.gmail.com/ and I went on a hunt to figure out how the heck this happened.

Turns out that if there is a fixup/squash chain where the *last* command fails with merge conflicts, and we either --skip ahead or resolve the conflict to a clean tree and then --continue, our code does not do a final cleanup.

Contrary to my initial gut feeling, this bug was not introduced by my rewrite in C of the core parts of rebase -i, but it looks to me as if that bug was with us for a very long time (at least the --skip part).

The developer (read: user of rebase -i) in me says that we would want to fast-track this, but the author of rebase -i in me says that we should be cautious and cook this in `next` for a while.

Fixes since v2 (thanks, Stefan!):

- Fixed commit message of 2/4: "Thisis" -> "This is".

- Reinstated the order where the `message-squash` file is renamed to
  `message` first, and only if that succeeded, we delete the
  `message-fixup` file.

Johannes Schindelin (4):
  rebase -i: demonstrate bugs with fixup!/squash! commit messages
  rebase -i: Handle "combination of <n> commits" with GETTEXT_POISON
  sequencer: leave a tell-tale when a fixup/squash failed
  rebase --skip: clean up commit message after a failed fixup/squash

 sequencer.c                | 94 ++++++++++++++++++++++++++++----------
 t/t3418-rebase-continue.sh | 22 +++++++++
 2 files changed, 93 insertions(+), 23 deletions(-)

base-commit: fe0a9eaf31dd0c349ae4308498c33a5c3794b293
Published-As: https://github.com/dscho/git/releases/tag/clean-msg-after-fixup-continue-v3
Fetch-It-Via: git fetch https://github.com/dscho/git clean-msg-after-fixup-continue-v3

Interdiff vs v2:
 diff --git a/sequencer.c b/sequencer.c
 index 881503a6463..b8b72fd540f 100644
 --- a/sequencer.c
 +++ b/sequencer.c
 @@ -2409,6 +2409,10 @@ static int error_failed_squash(struct commit *commit,
  {
  	const char *amend_type = "squash";
  
 +	if (rename(rebase_path_squash_msg(), rebase_path_message()))
 +		return error(_("could not rename '%s' to '%s'"),
 +			rebase_path_squash_msg(), rebase_path_message());
 +
  	if (file_exists(rebase_path_fixup_msg())) {
  		unlink(rebase_path_fixup_msg());
  		amend_type = "fixup";
 @@ -2418,9 +2422,6 @@ static int error_failed_squash(struct commit *commit,
  		return error(_("could not write '%s'"),
  			     rebase_path_amend_type());
  
 -	if (rename(rebase_path_squash_msg(), rebase_path_message()))
 -		return error(_("could not rename '%s' to '%s'"),
 -			rebase_path_squash_msg(), rebase_path_message());
  	unlink(git_path_merge_msg());
  	if (copy_file(git_path_merge_msg(), rebase_path_message(), 0666))
  		return error(_("could not copy '%s' to '%s'"),