From: Phillip Wood Date: Sun, 02 Jun 2019 14:17:13 GMT Subject: Re: [PATCH] add -p: coalesce hunks before testing applicability Message-ID: In-Reply-To: Hi Dscho Sorry it's taken me so long to get round to replying to this On 22/03/2019 14:06, Johannes Schindelin wrote: > Hi, > > On Thu, 13 Sep 2018, Phillip Wood wrote: > >> On 03/09/2018 20:01, Jochen Sprickerhof wrote: >> >>> * Phillip Wood [2018-08-30 14:47]: >>>> When $newhunk is created it is marked as dirty to prevent >>>> coalesce_overlapping_hunks() from coalescing it. This patch does not >>>> change that. What is happening is that by calling >>>> coalesce_overlapping_hunks() the hunks that are not currently selected >>>> are filtered out and any hunks that can be coalesced are (I think that >>>> in the test that starts passing with this patch the only change is the >>>> filtering as there's only a single hunk selected). >>> >>> Agreed here. It would be enough to include the first hunk in the test to >>> make it fail again. Still I would see the patch as going in the right >>> direction as we need something like coalesce_overlapping_hunks() to make >>> the hunks applicable after the edit. >> >> Yes in the long term we want to be able to coalesce edited hunks, but I >> think it is confusing to call coalesce_overlapping_hunks() at the moment >> as it will not coalesce the edited hunks. > > Agreed. I actually have code to coalesce even edited hunks, but it is all > in C. > >>>> This is a subtle change to the test for the applicability of an >>>> edited hunk. Previously when all the hunks were used to create the >>>> test patch we could be certain that if the test patch applied then if >>>> the user later selected any unselected hunk or deselected any >>>> selected hunk then that operation would succeed. I'm not sure that is >>>> true now (but I haven't thought about it for very long). >>> >>> I'm not sure here. If we use the same test from t3701, do s(plit), >>> y(es), e(dit), it would fail later on. Can you come up with an >>> example? >> >> I think that if you split a hunk, edit the first subhunk, transforming a >> trailing context line to a deletion then try if you try to stage the >> second subhunk it will fail. With your patch the edit will succeed as >> the second subhunk is skipped when testing the edited patch. Then when >> you try to stage the second subhunk it will fail as it's leading context >> will contradict the trailing lines of the edited subhunk. With the old >> method the edit failed but didn't store up trouble for the future. > > Indeed, this is a problem I also stumbled over. > >>>> We could restore the old test condition and coalesce the hunks by >>>> copying all the hunks and setting $hunk->{USE}=1 when creating the >>>> test patch if that turns out to be useful (it would be interesting to >>>> see if the test still passes with that change). >>> >>> We set USE=1 for $newhunk already, or where would you set it? >> >> To match the old test it needs to be set on the hunks we've skipped or >> haven't got to yet so they're all in the patch that's tested after >> editing a hunk. > > The way I fixed this in the C code is by teaching the equivalent of the > `coalesce_overlapping_hunks()` function to simply ignore the equivalent of > `$hunk->{USE}`: the function signature takes an additional `use_all` > parameter, which will override the `use` field. That sounds like a good solution. Thanks for working on the conversion to C, I'll try and find time look at the code on github. Best Wishes Phillip > > Furthermore, my C code actually does the coalescing as part of the > `reassemble_patch()` function, feeding the output directly into the > `stdin` of the `git apply` process (with, or without `--check`). > > And crucially, my C code does not try to assemble a new `hunks` array, but > simply works in-place, reverting the changes if the hunk edits result in a > patch that does not apply. The Perl version probably does not need that > part, as it is pretty careless with memory (as Perl encourages to do). > > See for yourself: > https://github.com/dscho/git/commit/6f8ac4809280f2cd018683ab5199b004ada2350e#diff-f58d2179be56b196b9f35c6d24799a8eR337 > > Ciao, > Dscho > > P.S.: Yes, this is part of my work to complete Slavica's "`git add -i` > in C" project. There are quite a few loose ends to tie, but I can already > use it myself to call `git add -p`, which is what I care most about, as it > regularly takes more than one second to spin up Perl on Windows, which is > friggin' annoying, I tell ya. >