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

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Apr 26, 2018, 09:51 UTC
Message-ID: <nycvar.QRO.7.76.6.1804261135530.4978@tvgsbejvaqbjf.bet>
In-Reply-To: <949b5749-d721-31ea-77a1-ec6406f3083a@talktalk.net>

Hi Phillip,

On Wed, 25 Apr 2018, Phillip Wood wrote:

Show 57 quoted lines

> On 25/04/18 13:48, Johannes Schindelin wrote:
> > 
> > On Mon, 23 Apr 2018, Phillip Wood wrote:
> > 
> > > On 23/04/18 19:11, Stefan Beller wrote:
> > > >
> > > > On Sat, Apr 21, 2018 at 12:34 AM, Johannes Schindelin
> > > > <johannes.schindelin@gmx.de> wrote:
> > > > > 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.
> > > >
> > > > I looked through the patches again and think this series is good
> > > > to go.
> > >
> > > I've just realized I commented on an outdated version as the new
> > > version was posted there rather than as a reply to v1. I've just
> > > looked through it and I'm not sure it addresses the unnecessary
> > > editing of the commit message of the previous commit if a single
> > > squash command is skipped as outlined in
> > > https://public-inbox.org/git/b6512eae-e214-9699-4d69-77117a0daec3@talktalk.net/
> > 
> > I have not forgotten about this! I simply did not find the time yet,
> > is all...
> 
> I wondered if that was the case but I wanted to check as I wasn't sure
> if you'd seen the original message as it was on an obsolete version of
> the series
> 
> > The patch series still has not been merged to `next`, but I plan on
> > working on your suggested changes as an add-on commit anyway. I am not
> > quite sure yet how I want to handle the "avoid running commit for the
> > first fixup/squash in the series" problem, but I think we will have to
> > add *yet another* file that is written (in the "we already have
> > comments in the commit message" conditional block in
> > error_failed_squash())...
> 
> I wonder if creating the file in update_squash_messages() rather than
> error_failed_squash() would be a better approach as then it is easy to
> only create rebase_path_amend_type() when there has already been a
> squash or fixup.  The file is removed in the loop that picks commits in
> pick_commits() so it would be cleaned up at the beginning of the next
> pick if it's not needed.

That would be a good idea in general, but I think we have to take care of the following scenario:

	pick	<- succeeds
	squash	<- succeeds
	fixup	<- fails, will be skipped

In this case, we do need to open the editor. But in this scenario, we do not:

	pick	<- succeeds
	fixup	<- succeeds
	squash	<- fails, will be skipped

If we write the amend-type file in update_squash_messages(), we would write "squash" into it in both cases. My hope was to somehow avoid that.

I just realized that the current iteration does not fulfill that goal, as the message-fixup file would be long gone by the time error_failed_squash() was called in the latter example.

Also, I realized something else: my previous work-around for the GETTEXT_POISON case (where I fail gently when a commit message does not contain the "This is a combination of #<count> commits" count in ASCII) would be much superior if it simply would not abuse the comment in the commit message, but had a robust, non-l18ned way to count the fixup/squash commits.

My current thinking is to reconcile both problems by shunning the amend-type and instead just record the sequence of fixup/squash commits that went into HEAD, in a new file, say, current-fixups.

To answer the question how many commit messages are combined, I then simply need to count the lines in that file.

To answer the question whether a skipped fixup/squash requires the editor to be launched, I can simply look whether there is a "squash" line (ignoring the last line).

Oh, and I also forgot to test whether this is the "final fixup". If we are skipping a "fixup" in the middle of a chain, there is no need to clean the commit message to begin with.

This will take a while... ;-)

Ciao, Dscho