[0/2] rebase: fix 2.11.0-era --fork-point regression

Message

Ævar Arnfjörð Bjarmason Feb. 21, 2019, 9:40 p.m. UTC

On Thu, Feb 21 2019, Jeff King wrote:

> On Thu, Feb 21, 2019 at 03:50:38PM +0100, Ævar Arnfjörð Bjarmason wrote:
>
>> > Those aren't using "--fork-point", so they're going to behave
>> > differently. The default with no arguments is basically "--fork-point
>> > @{u}".
>> 
>> Yeah, that's what it *should* do, but it's not equivalent to using
>> --fork-point manually:
>> 
>>     # my series on top of origin/master
>>     $ git rev-parse HEAD
>>     2a67977d3f70fa7fc4bce89db24a1218dc9ab2aa
>>     
>>     # Junio's origin/master upstream
>>     $ git rev-parse @{u}
>>     35ee755a8c43bcb3c2786522d423f006c23d32df
>>     
>>     # Where my fork point is
>>     $ git merge-base --fork-point @{u}
>>     35ee755a8c43bcb3c2786522d423f006c23d32df
>>     
>>     # OK
>>     $ git rebase 35ee755a8c43bcb3c2786522d423f006c23d32df
>>     Current branch master is up to date.
>>     
>>     # OK
>>     $ git rebase $(git merge-base --fork-point @{u})
>>     Current branch master is up to date.
>>     
>>     # ???
>>     $ git rebase
>>     First, rewinding head to replay your work on top of it...
>>     [...]
>
> Have you tried with "git rebase --fork-point"? It does more than just
> pass --fork-point to merge-base. It seems to also skip some of the "is
> up to date", I think due to 1e0dacdbdb (rebase: omit patch-identical
> commits with --fork-point, 2014-07-16).
>
> I'm still not clear on whether my 4f21454b55 actually changed something
> menaingful here, or if it's simply that you're getting the fork-point
> behavior more consistently.

Yes it's a regression. Here's a fix for it. As seen in 2/2 how we got
to the point of regressing was an interesting combination of factors.

Ævar Arnfjörð Bjarmason (2):
  rebase tests: test linear branch topology
  rebase: don't rebase linear topology with --fork-point

 builtin/rebase.c                  |  6 +++--
 t/t3421-rebase-topology-linear.sh | 44 +++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 2 deletions(-)