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Re: git rebase regression: cannot pass a shell expression directly to --exec

From
Kevin Daudt <me@ikke.info>
Date
May 16, 2017, 17:14 UTC
Message-ID
<20170516171414.GC2169@alpha.vpn.ikke.info>
In-Reply-To
<CA+zRj8Uxh1SGdVW=zz29Q4m4OnDcs665T0XtV6FiZ_qZSiG-8g@mail.gmail.com>
On Tue, May 16, 2017 at 09:59:03AM -0700, Eric Rannaud wrote:
Show 21 quoted lines
> On Tue, May 16, 2017 at 9:18 AM, Jeff King <peff@peff.net> wrote:
> > On Tue, May 16, 2017 at 12:23:02PM +0200, Johannes Schindelin wrote:
> >> It would appear to me that you used a side effect of an implementation
> >> detail: that `git rebase -i` was implemented entirely as a shell script.
> >
> > I don't think that's true at all. He expected the user-provided "--exec"
> > command to be run by a shell, which seems like a reasonable thing for
> > Git to promise (and we already make a similar promise for most
> > user-provided commands that we run).  What happens in between, be it
> 
> As a "user", my expectation was simply that the command would be run
> not just in "a shell", but in *my* shell (or the shell that calls git,
> maybe). So I don't see any portability question with respect to Git.
> My script that uses git rebase --exec may not be portable, but that's
> my problem.
> 
> When I use "git rebase --exec <cmd>" I'm basically writing a "foreach
> commit in range { <cmd> }" in my shell. Same idea with git bisect run.
> 
> A transparent optimization that tries execve() then falls back to the
> user's shell sounds like a good idea.

It does not really work that way. Git runs in a separate process that does not have access to your current shell. That's why you need to do 'export -f foo'.

If you want git to be able to ecute the foo shell function, git needs to start a _new_ shell process, which reads the environment, recognize the exported function and run that.

This is not the same as git executing the command in your shell. Not exported variables would not be available in this function (as it would be in your equivalent).

Previous: Eric RannaudNext: Eric Rannaud
Message 25 of 29 in “git rebase regression: cannot pass a shell expression directly to --exec”
  1. Eric RannaudMay 15, 2017
  2. Jeff KingMay 16, 2017
  3. Jeff KingMay 16, 2017
  4. Jonathan NiederMay 16, 2017
  5. Jeff KingMay 16, 2017
  6. Eric RannaudMay 16, 2017
  7. Brandon WilliamsMay 16, 2017
  8. Jeff KingMay 16, 2017
  9. Brandon WilliamsMay 16, 2017
  10. Linus TorvaldsMay 16, 2017
  11. [TANGENT] run-command: use vfork instead of forkEric Wong, May 16, 2017
  12. Linus TorvaldsMay 16, 2017
  13. Brandon WilliamsMay 16, 2017
  14. Johannes SchindelinMay 16, 2017
  15. Linus TorvaldsMay 16, 2017
  16. Jonathan NiederMay 16, 2017
  17. Junio C HamanoMay 16, 2017
  18. Jeff KingMay 16, 2017
  19. Jeff KingMay 16, 2017
  20. Eric RannaudMay 16, 2017
  21. Johannes SchindelinMay 16, 2017
  22. Johannes SchindelinMay 16, 2017
  23. Jeff KingMay 16, 2017
  24. Eric RannaudMay 16, 2017
  25. Kevin DaudtMay 16, 2017
  26. Eric RannaudMay 16, 2017
  27. Jeff KingMay 16, 2017
  28. Eric RannaudMay 16, 2017
  29. Jeff KingMay 16, 2017

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