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Re: [PATCH] rebase: use reflog to find common base with upstream

From
John Keeping <john@keeping.me.uk>
Date
Oct 21, 2013, 11:24 UTC
Message-ID
<20131021112408.GA24317@serenity.lan>
In-Reply-To
<CANiSa6gqGKAyLwwPVoZ_gzN85_06aTCfkdRRscNNZYs7g1rL0A@mail.gmail.com>
On Sun, Oct 20, 2013 at 10:03:29PM -0700, Martin von Zweigbergk wrote:
Show 36 quoted lines
> On Wed, Oct 16, 2013 at 11:53 AM, John Keeping <john@keeping.me.uk> wrote:
> > Commit 15a147e (rebase: use @{upstream} if no upstream specified,
> > 2011-02-09) says:
> >
> >         Make it default to 'git rebase @{upstream}'. That is also what
> >         'git pull [--rebase]' defaults to, so it only makes sense that
> >         'git rebase' defaults to the same thing.
> >
> > but that isn't actually the case.  Since commit d44e712 (pull: support
> > rebased upstream + fetch + pull --rebase, 2009-07-19), pull has actually
> > chosen the most recent reflog entry which is an ancestor of the current
> > branch if it can find one.
> 
> It is exactly this inconsistency between "git rebase" and "git pull
> --rebase" that confused me enough to make me send my first email to
> this list almost 4 years ago [1], so thanks for working on this! I
> finished that thread with:
> 
>   Would it make sense to teach "git rebase" the same tricks as "git
> pull --rebase"?
> 
> Then it took me a year before I sent a patch not unlike this one [2].
> To summarize, the patch did not get accepted then because it makes
> rebase a little slower (or a lot slower in some cases). "git pull
> --rebase" is of course at least as slow in the same cases, but because
> it often involves connecting to a remote host, people would probably
> blame the connection rather than git itself even in those rare (?)
> cases.
> 
> I think
> 
>   git merge-base HEAD $(git rev-list -g "$upstream_name")
> 
> is roughly correct and hopefully fast enough. That can lead to too
> long a command line, so I was planning on teaching merge-base a
> --stdin option, but never got around to it.

I'm not sure we should worry about the additional overhead here. In the common case, we should hit a common ancestor within the first couple of reflog entries; and in the case that will be slow, it's likely that there are a lot of differences between the branches so the cherry comparison phase will take a while anyway.

Previous: Martin von ZweigbergkNext: Martin von Zweigbergk
Message 5 of 35 in “rebase: use reflog to find common base with upstream”
  1. rebase: use reflog to find common base with upstreamJohn Keeping, Oct 16, 2013
  2. Jonathan NiederOct 16, 2013
  3. John KeepingOct 16, 2013
  4. Martin von ZweigbergkOct 21, 2013
  5. John KeepingOct 21, 2013
  6. Martin von ZweigbergkOct 22, 2013
  7. Junio C HamanoOct 24, 2013
  8. 0/2 finding the fork point from reflog entriesJunio C Hamano, Oct 24, 2013
  9. 1/2 merge-base: use OPT_CMDMODE and clarify the command line parsingJunio C Hamano, Oct 24, 2013
  10. 2/2 merge-base: "--reflog" mode finds fork point from reflog entriesJunio C Hamano, Oct 24, 2013
  11. Eric SunshineOct 24, 2013
  12. Junio C HamanoOct 24, 2013
  13. Eric SunshineOct 24, 2013
  14. Junio C HamanoOct 24, 2013
  15. 2/2 merge-base: "--reflog" mode finds fork point from reflog entriesJunio C Hamano, Oct 24, 2013
  16. Johannes SixtOct 25, 2013
  17. John KeepingOct 25, 2013
  18. Johannes SixtOct 25, 2013
  19. Junio C HamanoOct 25, 2013
  20. 2/2 merge-base: teach "--fork-point" modeJunio C Hamano, Oct 25, 2013
  21. Eric SunshineOct 25, 2013
  22. Martin von ZweigbergkOct 26, 2013
  23. Junio C HamanoOct 28, 2013
  24. John KeepingOct 26, 2013
  25. Junio C HamanoOct 28, 2013
  26. John KeepingOct 29, 2013
  27. Junio C HamanoOct 29, 2013
  28. John KeepingOct 24, 2013
  29. Junio C HamanoOct 24, 2013
  30. John KeepingOct 24, 2013
  31. John KeepingOct 24, 2013
  32. John KeepingOct 24, 2013
  33. Junio C HamanoOct 25, 2013
  34. Martin von ZweigbergkOct 22, 2013
  35. John KeepingOct 24, 2013

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