From: "Lars Hjemli" <hjemli@gmail.com>
To: "Andreas Ericsson" <ae@op5.se>
Cc: "Junio C Hamano" <gitster@pobox.com>, git@vger.kernel.org
Subject: Re: [PATCH] git-merge: add option --no-ff
Date: Mon, 17 Sep 2007 15:16:54 +0200 [thread overview]
Message-ID: <8c5c35580709170616i49a8836hb60423c5eebf601d@mail.gmail.com> (raw)
In-Reply-To: <46EE7584.8010202@op5.se>
On 9/17/07, Andreas Ericsson <ae@op5.se> wrote:
> Lars Hjemli wrote:
> > This new option forces all merges to create a "true" merge commit, i.e. a
> > commit with multiple parents.
> >
> > Although a fast-forward would normally be The Right Thing, it isn't when the
> > branches to be merged originated in subversion and the merge commit will
> > be pushed back by means of 'git svn dcommit'. In these cases, a fast-
> > forward merge simply will not work.
> >
> > If there is no `-s` option, a built-in list of strategies
> > is used instead (`git-merge-recursive` when merging a single
> > head, `git-merge-octopus` otherwise).
> > +
> > +--no-ff::
> > + Force the creation of a merge commit even when the merge would
> > + have resolved as a fast-forward operation.
>
> + Although a fast-forward would normally be The Right Thing, it isn't when the
> + branches to be merged originated in subversion and the merge commit will
> + be pushed back by means of 'git svn dcommit'. In these cases, a fast-
> + forward merge simply will not work.
>
> Otherwise someone will sit down and try to figure out why this is necessary.
True.
> I'm having trouble understanding why this is needed, but I'll take your word
> for it ;-)
I'll try to explain:
When 'git-svn dcommit' decides which commits it should push back
subversion, it scans the output from 'git-log --first-parent HEAD'
looking for embedded 'git-svn-id' lines. These lines contain the url
of the upstream subversion repository + the subversion revision
number. So the problem with fast-forward merges of subversion branches
is that the output from 'git-log --first-parent HEAD' will show
commits from the wrong subversion branch (the fast-forwarded commits).
This could maybe be fixed in git-svn if it learned a different way of
discovering the upstream subversion branch, but then it would make
git-svn commit n revisions to subversion (again, the fast-forwarded
commits) instead of a single merge-commit. This would look (in
subversion) like a series of n cherry-picks from the merged branch.
Btw: maybe the --no-ff section in merge-options.txt could just link to
git-svn.txt, which in turn could have some lengthy explanation about
merge --no-ff/dcommit behaviour?
--
larsh
next prev parent reply other threads:[~2007-09-17 13:17 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-17 12:17 [PATCH] git-merge: add option --no-ff Lars Hjemli
2007-09-17 12:39 ` Andreas Ericsson
2007-09-17 13:16 ` Lars Hjemli [this message]
2007-09-17 13:23 ` Johannes Schindelin
2007-09-17 13:37 ` Chris Shoemaker
2007-09-17 13:40 ` Lars Hjemli
2007-09-17 13:52 ` Johannes Schindelin
2007-09-17 13:38 ` Lars Hjemli
2007-09-17 13:57 ` Johannes Schindelin
2007-09-17 14:12 ` Lars Hjemli
2007-09-17 15:05 ` Johannes Schindelin
2007-09-17 15:17 ` Lars Hjemli
2007-09-17 16:23 ` Lars Hjemli
2007-09-18 0:50 ` Eric Wong
2007-09-18 1:09 ` Junio C Hamano
2007-09-18 1:39 ` Eric Wong
2007-09-18 6:12 ` Lars Hjemli
2007-09-18 6:23 ` Eric Wong
2007-09-18 6:53 ` Junio C Hamano
2007-09-18 7:30 ` Sam Vilain
2007-09-18 9:12 ` Sam Vilain
2007-09-18 11:19 ` Lars Hjemli
2007-09-18 11:50 ` Sam Vilain
2007-09-18 12:03 ` Lars Hjemli
2007-09-18 13:22 ` Sam Vilain
2007-09-18 14:01 ` Lars Hjemli
2007-09-18 14:34 ` Sam Vilain
2007-09-18 12:29 ` Johannes Schindelin
2007-09-18 12:38 ` Lars Hjemli
2007-09-18 8:02 ` Lars Hjemli
2007-09-18 22:51 ` Peter Baumann
2007-09-19 7:09 ` Lars Hjemli
2007-09-17 16:07 ` Chris Shoemaker
2007-09-17 16:14 ` Lars Hjemli
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