Re: [RFC][GSoC] Project proposal: convert interactive rebase to C

From: Alban Gruin <alban.gruin@gmail.com>
Date: Mar 21, 2018, 11:04 UTC
Message-ID: <46112353.MVnaADNoVi@andromeda>
In-Reply-To: <nycvar.QRO.7.76.6.1803201720090.55@ZVAVAG-6OXH6DA.rhebcr.pbec.zvpebfbsg.pbz>

Hi Johannes,

Le mardi 20 mars 2018 17:29:28 CET, vous avez écrit :

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> > Weeks 1 & 2 — May 14, 2018 – May 28, 2018
> > First, I would refactor --preserve-merges in its own shell script, as
> > described in Dscho’s email.
> 
> Could you go into detail a bit here? Like, describe what parts of the
> git-rebase--interactive.sh script would need to be duplicated, which ones
> would be truly moved, etc
>

It would lead to duplicate a good chunk of git_rebase__interactive(), apparently. The moved parts would be everything in `if test t = "$preserve_merges"; then …; fi` statements. That is, about 50 lines of shell code.

Judging by that, beginning by that is probably not the right thing to do. Also, somebody is already working on that[1].

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> > Weeks 3 & 4 — May 18, 2018 – June 11, 2018
> > Then, I would start to rewrite git-rebase--interactive, and get rid of
> > git-
> > rebase--helper.
> 
> I think this is a bit premature, as the rebase--helper would not only
> serve the --interactive part, but in later conversions also --am and
> --merge, and only in the very end, when git-rebase.sh gets converted,
> would we be able to simply rename the rebase--helper to rebase.
>

Yes, Christian Couder told me that it would not be a good methodology too.

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> Also, I have a hunch that there is actually almost nothing left to rewrite
> after my sequencer improvements that made it into Git v2.13.0, together
> with the upcoming changes (which are on top of the --recreate-merges patch
> series, hence I did not send them to the mailing list yet) in
> https://github.com/dscho/git/commit/c261f17a4a3e

One year ago, you said[2] that converting this script "will fill up 3 month, very easily". Is this not accurate anymore?

> 
> So I would like to see more details here... ;-)

Yep, I’m working on that.

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> > Weeks 5 to 9 — June 11, 2018 – July 15, 2018
> > During this period, I would continue to rewrite git-rebase--interactive.
> 
> It would be good if the proposal said what parts of the conversion are
> tricky, to merit spending a month on them.
> 
> > Weeks 10 & 11 — July 16, 2018 – July 29, 2018
> > In the second half of July, I would look for bugs in the new code, test
> > it,
> > and improve its coverage.
> 
> As I mentioned in a related mail, the test suite coverage would be most
> sensibly extended *before* starting to rewrite code in C, as it helps
> catching bugs early and avoids having to merge buggy code that needs to be
> fixed immediately.

Makes sense.

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> 
> > Weeks 12 — July 30, 2018 – August 5, 2018
> > In the last week, I would polish the code where needed, in order to
> > improve for performance or to make the code more readable.
> 
> Thank you for sharing this draft with us!
> Johannes

I’ll send a new draft as soon as possible (hopefully this afternoon).

Thank you for your enthousiasm :) Alban

[1] https://public-inbox.org/git/20180320204507.12623-1-wink@saville.com/ [2] https://public-inbox.org/git/alpine.DEB. 2.20.1703231827060.3767@virtualbox/