git@vger.kernel.org list mirror (unofficial, one of many)
 help / color / mirror / code / Atom feed
From: Phil Hord <phil.hord@gmail.com>
To: Jakub Narebski <jnareb@gmail.com>
Cc: "Junio C Hamano" <gitster@pobox.com>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Giuseppe Crinò" <giuscri@gmail.com>, Git <git@vger.kernel.org>
Subject: Re: Feature request: Allow to update commit ID in messages when rebasing
Date: Thu, 18 Apr 2019 11:00:23 -0700	[thread overview]
Message-ID: <CABURp0r_0pTY9JAsphm-TUBVCarK8h8SmO-v8zf7OPzf+7=SJw@mail.gmail.com> (raw)
In-Reply-To: <86o953z0b9.fsf@gmail.com>

Wouldn't we need to extend this to cherry-pick, too?  Suppose I do this:

    $ git log -2 --oneline --decorate foo
    abcd123456  (foo)   Revert 123456aaaa
    123456aaaa  Some useful commit for the future, but not now

    $ git checkout bar
    $ git cherry-pick foo^ foo

    $ git log -2 --oneline --decorate
    badc0ffee  (bar)   Revert 123456aaaa
    babeface0  Some useful commit for the future, but not now

Now when I rebase bar, the revert appears to be untwinned.

Similar problems arise for other history modifying tools like
filter-branch, fast-export, reposurgeon, bfg, etc.

I guess we can use 'git patch-id' to see if the companion commit is
still in our history, but this seems tenuous.  Can we make it work
anyway?


On Thu, Apr 18, 2019 at 10:33 AM Jakub Narebski <jnareb@gmail.com> wrote:
>
> Junio C Hamano <gitster@pobox.com> writes:
> > Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
> >> On Wed, Apr 17 2019, Giuseppe Crinò wrote:
> >>
> >>> The feature I'm asking is to add an extra-step during rebasing,
> >>> checking whether there's a reference to a commit that's not going to
> >>> be included in history and asks the user whether the heuristics is
> >>> correct and if she wants to update those references.
> >>>
> >>> Scenario: it can happen for a commit message to contain the ID of an
> >>> ancestor commit. A typical example is a commit with the message
> >>> "revert 01a9fe8". If 01a9fe8 and the commit that reverts it are
> >>> involved in a rebase the message "revert 01a9fe8" is no longer valid
> >>> -- the old 01a9fe8 has now a different hash. This will most likely be
> >>> ignored by the person who's rebasing but will let the other people
> >>> reading history confused.
> >>
> >> This would be useful. Done properly we'd need some machinery/command to
> >> extract the commit id parts from the free-text of the commit
> >> message. That would be useful for other parts of git, e.g. as discussed
> >> here:
> >> https://public-inbox.org/git/xmqqvaxp9oyp.fsf@gitster.mtv.corp.google.com/
> >
> > That's a helpful input.
> >
> > But in general we do not have an infrastructure to systematically
> > keep track of "this commit was rewritten to produce that other
> > commit", so even if a mention of an old/superseded commit can be
> > identified reliably, there is no reliable source to rewrite it to
> > the name of the corresponding commit in the new world.
> >
> > For that mapping, we'd need something like the "git change/evolve"
> > Stefan Xenos was working on, which hasn't materialized.
>
> Well, what about limiting changes and rewriting only to the commits
> being rewritten by [interactive] rebase?  I mean that we would rewrite
> "revert 01a9fe8" only if:
>
> a.) the commit with this message is undergoing rewrite
> b.) the commit 01a9fe8 is undergoing rewrite in the same command
>
> We could use the infrastructure from git-filter-branch for this.
>
> It is serious limitation, but that might be good enough for Giuseppe
> Crinò use case.  Though for example there is a question what to do if
> referred-to commit (01a9fe8 in the example) is simply dropped, or is
> gets split in two?  Ask user?
>
>
> Another possibility would be to provide a command line option to rebase
> which would automatically generate replacements (in git-replace meaning)
> from old pre-rebase name to new post-rebase name (assuming no splitting,
> no dropping commits).  This would make references just work... well, as
> long as refs/replace/* are in place (they are not copied by default).
>
> On the other hand some of our performance-improving features, like the
> commit-graph, do not work if there are replacements.
>
>
> Best,
> --
> Jakub Narębski

      parent reply	other threads:[~2019-04-18 18:32 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-17 20:35 Giuseppe Crinò
2019-04-17 20:56 ` Ævar Arnfjörð Bjarmason
2019-04-18  2:08   ` Junio C Hamano
2019-04-18 17:32     ` Jakub Narebski
2019-04-18 17:58       ` Giuseppe Crinò
2019-04-19 10:44         ` Jakub Narebski
2019-04-18 18:00       ` Phil Hord [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: http://vger.kernel.org/majordomo-info.html

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CABURp0r_0pTY9JAsphm-TUBVCarK8h8SmO-v8zf7OPzf+7=SJw@mail.gmail.com' \
    --to=phil.hord@gmail.com \
    --cc=avarab@gmail.com \
    --cc=git@vger.kernel.org \
    --cc=gitster@pobox.com \
    --cc=giuscri@gmail.com \
    --cc=jnareb@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
Code repositories for project(s) associated with this inbox:

	https://80x24.org/mirrors/git.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).