Propose promoting 'contrib/rerere-train.sh' to command

> I would like to propose promoting 'contrib/rerere-train.sh' to one of the
> following:
>
>     1. A builtin c command 'builtin/rerere-train.c'
>     2. To the top level directory as a built in script 'git-rerere-train.sh'
>
> I have recently found myself writing scripts using 'contrib/rerere-train.sh'
> and I wish it was built into the command. This would make it easier to use
> rather than having to find it on different platforms. I think it could also
> benefit from some documentation.
>
> I am trying to gauge the interest in this change before spending some time on
> working on it. I would also appreciate feedback or alternative approaches to
> what I have suggested. Thank you for your time.
>
> Thanks,
> Tom Miller

> Hi Tom,
>
> On 21/12/2019 02:17, Tom Miller wrote:
>> I would like to propose promoting 'contrib/rerere-train.sh' to one of the
>> following:
>>
>>     1. A builtin c command 'builtin/rerere-train.c'
>>     2. To the top level directory as a built in script 'git-rerere-train.sh'
>>
>> I have recently found myself writing scripts using 'contrib/rerere-train.sh'
>> and I wish it was built into the command. This would make it easier to use
>> rather than having to find it on different platforms. I think it could also
>> benefit from some documentation.
>>
>> I am trying to gauge the interest in this change before spending some time on
>> working on it. I would also appreciate feedback or alternative approaches to
>> what I have suggested. Thank you for your time.
>>
>> Thanks,
>> Tom Miller
> This sounds like a useful capability (especially the documentation!).
>
> I also had aspirations that there should also be a way of exchanging the
> essence of the rerere data when conflicts (e.g. feature vs master branch
> merges) are known locally and ought to be communicable with the patch sets.
>
> see messages:
> <37ccaad0-40b4-ca63-e057-791119d7fa69@talktalk.net>
> <nycvar.QRO.7.76.6.1909261253400.15067@tvgsbejvaqbjf.bet>
>
> Philip

> I would like to propose promoting 'contrib/rerere-train.sh' to one of the
> following:
> 
>     1. A builtin c command 'builtin/rerere-train.c'
>     2. To the top level directory as a built in script 'git-rerere-train.sh'
> 
> I have recently found myself writing scripts using 'contrib/rerere-train.sh'
> and I wish it was built into the command. This would make it easier to use
> rather than having to find it on different platforms. I think it could also
> benefit from some documentation.
> 
> I am trying to gauge the interest in this change before spending some time on
> working on it. I would also appreciate feedback or alternative approaches to
> what I have suggested. Thank you for your time.

> Jeff King <peff@peff.net> writes:
> 
> > The situations where I need rerere-train don't come up often, but when
> > they do, it has always worked easily and without hiccups for me. So
> > perhaps there are lurking gotchas that Junio might know about, but AFAIK
> > the quality is high enough for it to be part of normal Git.
> 
> I actually suspect that rewriting has a high chance of initially
> degrading the quality, so we should take a two step approach if we
> really want it as part of the core distribution.  As to the UI, I
> think "git rerere train a..b" would be a good one, but if the
> scripted version is of high quality (I haven't looked at it for a
> long time---even though I used it for a couple of times a year in
> recent years), perhaps we can add it as "git-rerere--train"
> subcommand that is spawned from "builtin/rerere.c" for the first
> cut?

> On Sat, Dec 21, 2019 at 03:52:53PM -0800, Junio C Hamano wrote:
>
> 
> > Jeff King <peff@peff.net> writes:
> > 
> > > The situations where I need rerere-train don't come up often, but when
> > > they do, it has always worked easily and without hiccups for me. So
> > > perhaps there are lurking gotchas that Junio might know about, but AFAIK
> > > the quality is high enough for it to be part of normal Git.
> > 
> > I actually suspect that rewriting has a high chance of initially
> > degrading the quality, so we should take a two step approach if we
> > really want it as part of the core distribution.  As to the UI, I
> > think "git rerere train a..b" would be a good one, but if the
> > scripted version is of high quality (I haven't looked at it for a
> > long time---even though I used it for a couple of times a year in
> > recent years), perhaps we can add it as "git-rerere--train"
> > subcommand that is spawned from "builtin/rerere.c" for the first
> > cut?
>
> 
> Yeah, I'd be pretty happy with that, too.
>
> 
> I just suspect its ultimate fate is conversion to C, given the general
> trend. And converting it to C that just calls out to other git commands
> via run_command would presumably behave just like the original, leaving
> the more challenging and error-prone conversion for later. Hopefully any
> upgrade to "real Git command" would include some tests, though. :)
>
> 
> -Peff

> On Sun Dec 22, 2019 at 2:58 AM, Jeff King wrote:
> > On Sat, Dec 21, 2019 at 03:52:53PM -0800, Junio C Hamano wrote:
> >
> >
> > > Jeff King <peff@peff.net> writes:
> > >
> > > > The situations where I need rerere-train don't come up often, but when
> > > > they do, it has always worked easily and without hiccups for me. So
> > > > perhaps there are lurking gotchas that Junio might know about, but AFAIK
> > > > the quality is high enough for it to be part of normal Git.
> > >
> > > I actually suspect that rewriting has a high chance of initially
> > > degrading the quality, so we should take a two step approach if we
> > > really want it as part of the core distribution.  As to the UI, I
> > > think "git rerere train a..b" would be a good one, but if the
> > > scripted version is of high quality (I haven't looked at it for a
> > > long time---even though I used it for a couple of times a year in
> > > recent years), perhaps we can add it as "git-rerere--train"
> > > subcommand that is spawned from "builtin/rerere.c" for the first
> > > cut?
> >
> >
> > Yeah, I'd be pretty happy with that, too.
> >
> >
> > I just suspect its ultimate fate is conversion to C, given the general
> > trend. And converting it to C that just calls out to other git commands
> > via run_command would presumably behave just like the original, leaving
> > the more challenging and error-prone conversion for later. Hopefully any
> > upgrade to "real Git command" would include some tests, though. :)
> >
> >
> > -Peff
>
> Thanks for the feedback everyone! This is roughly the feedback I
> expected. I think moving the shell version first will give more time to
> focus on getting a strong test harness in place and a some decent
> documentation. I happy with doing this in a multi phase approach as it
> introduces less risk. When I get to the point of writing it in C I will
> try to do the work internally by looking at commits as Jeff has
> suggested, and fall back to run commands if I have to.