Re: Bug with fixup and autosquash

From: Philip Oakley <philipoakley@iee.org>
Date: Feb 9, 2017, 23:34 UTC
Message-ID: <454E7D934160418EB4C4871ED209CBCA@PhilipOakley>
In-Reply-To: <alpine.DEB.2.20.1702092142020.3496@virtualbox>

From: "Johannes Schindelin" <Johannes.Schindelin@gmx.de>
Sent: Thursday, February 09, 2017 8:55 PM

Show 47 quoted lines

> Hi Ashutosh and Junio,
>
> On Wed, 8 Feb 2017, Junio C Hamano wrote:
>
>> Ashutosh Bapat <ashutosh.bapat@enterprisedb.com> writes:
>>
>> > I have been using git rebase heavily these days and seem to have found
>> > a bug.
>> >
>> > If there are two commit messages which have same prefix e.g.
>> > yyyyyy This is prefix
>> > xxxxxx This is prefix and message
>> >
>> > xxxxxx comitted before yyyyyy
>> >
>> > Now I commit a fixup to yyyyyy using git commit --fixup yyyyyy
>> > zzzzzz fixup! This is prefix
>> >
>> > When I run git rebase -i --autosquash, the script it shows me looks 
>> > like
>> > pick xxxxxx This is prefix and message
>> > fixup zzzzzz fixup! This is prefix
>> > pick yyyyyy This is prefix
>> >
>> > I think the correct order is
>> > pick xxxxxx This is prefix and message
>> > pick yyyyyy This is prefix
>> > fixup zzzzzz fixup! This is prefix
>> >
>> > Is that right?
>>
>> [...]
>>
>> Unfortunately, "rebase -i --autosquash" reorders the entries by
>> identifying the commit by its title, and it goes with prefix match so
>> that fix-up commits created without using --fixup option but manually
>> records the title's prefix substring can also work.
>
> This prefix match also happens to introduce a serious performance problem,
> which is why I "fixed" this issue in the rebase--helper already (which is
> the case if you are using Git for Windows, whose master branch builds on
> Linux and MacOSX as well). I quoted "fix" because my motivation was to fix
> the performance problem, not the "incorrect match" problem.
>
> The rebase--helper code (specifically, the patch moving autosquash logic
> into it: https://github.com/dscho/git/commit/7d0831637f) tries to match
> exact onelines first,

While I think this is an improvement, and will strongly support the `git commit --fixup=<commit>` option which will, if the sha1/oid is given, create the exact commit subject line.

However it would also be useful if the actual commit subject line could have a similar format option, so that those who use say the git gui (rather than the cli) for the commit message, could easily create the `!fixup <commit>` message which would allow a broader range of ways of spelling the commit (e.g. giving a sha1(min length) that is within the rebase todo list).

Show 17 quoted lines

> and falls back to prefix matching only after that.
>
> Now that the sequencer-i patch series is in `master`, the next step is to
> send the patch series introducing the rebase--helper. The patch series
> including the fix discussed above relies on that one. Meaning that it will
> take a while to get through the mill.
>
> So please do not hold your breath until this feature/fix hits an official
> Git version. If you need it[*1*] faster, feel free to build Git for
> Windows' master and run with that for a while.
>
> Ciao,
> Johannes
>
> Footnote: By "it" I mean "the feature/fix", not "an official Git version"
> nor "your breath".
>

-- Philip