Subject: Re: [REGRESSION] gitk can't be run from non-worktree folders

From: SZEDER Gábor <[email-masked]>
Date: Thu, 23 Jan 2020 18:46:02 +0100

On Thu, Jan 23, 2020 at 06:04:12PM +0100, SZEDER Gábor wrote:
> On Thu, Jan 23, 2020 at 11:36:49AM -0500, Eric Sunshine wrote:

> > > Are you sure it's a recent regression?  I have no experience with
> > > 'gitk' in Git for Windows, but on Linux this has been broken for quite
> > > some time, namely since 784b7e2f25 (gitk: Fix "External diff" with
> > > separate work tree, 2011-04-04) in the v1.7 era.  FWIW, reverting that
> > > commit on top of v2.25.0 makes 'gitk' work again in bare repositories.
> > 
> > It's a new regression introduced by 2d92ab32fd (rev-parse: make
> > --show-toplevel without a worktree an error, 2019-11-19), as far as I
> > can tell.
> 
> Oh, that's interesting.
> 
> My local commit reverting 784b7e2f25 that I build my Git with is newer
> than 2d92ab32fd, so maybe that's why I haven't recalled seeing this
> issue earlier.  I did try to bisect it, but had a real hard time with
> gitk being subtree merged, and ultimately gave up on that, and started
> to look for a commit adding '--show-toplevel' to 'gitk', which lead me
> to 784b7e2f25, I reverted it, my issue went away, which then lead me
> to the wrong conclusion.

Oh, this is interesting indeed :)

I have a couple of older Git versions lying around, so I can quickly
ballpark a revision range for a regression, without checking out and
building older versions.  This has always worked well so far, because
Git looks for its non-builtin commands in the hardcoded exec-path that
was specified at build time, while builtin commands are, well,
builtins.  Alas, 'gitk' is not a regular Git command, and it runs
whatever 'git' executable comes first in PATH, which in my case was a
recent build already containing 2d92ab32fd.

  $ ~/src/git/BUILDS/v1.8.0/bin/git --exec-path
  /home/szeder/src/git/BUILDS/v1.8.0/libexec/git-core
  $ cd .git
  $ ~/src/git/BUILDS/v1.8.0/bin/gitk
  Error in startup script: fatal: this operation must be run in a work
  tree
      while executing
  "exec git rev-parse --show-toplevel"
      invoked from within
  "set worktree [exec git rev-parse --show-toplevel]"
      (file "/home/szeder/src/git/BUILDS/v1.8.0/bin/gitk" line 11810)
  $ PATH=~/src/git/BUILDS/v1.8.0/bin:"$PATH" ~/src/git/BUILDS/v1.8.0/bin/gitk
  # Works even in the .git directory!
  $ PATH=~/src/git/BUILDS/v2.24.0/bin:"$PATH" ~/src/git/BUILDS/v2.24.0/bin/gitk
  # This works, too!

With this newly gained knowledge I added 'bin-wrappers' to $PATH when
running gitk built from 2d92ab32fd and its parent, and indeed that's
the commit that introduced this regression.