use git rev-parse to look for config file

[bdauvergne]

It fixes config file finding when in a separate worktree.

If fixes the issue with worktree reported in #719 (comment)

[Byron]

It looks like there is test breakage directly related to this commit.
Could you have a look?

[Byron]

Thanks a lot for the contribution - I would love to merge, but can't as long as there is test breakage. Maybe it's an easy fix.

[bdauvergne]

I tried a work-around but i'm not sure of it, there is some circular dependency between the search got the .git directory in Repo and the initialization of the self.git command wrapper (the git command should be able to find the .git itself, but the late initialization has maybe some use).

[bdauvergne]

And it works (I don't know the problem with appveyor, I do not think it's related to my patch).

[codecov-io]

Codecov Report

Merging #894 into master will decrease coverage by 0.02%.
The diff coverage is 95.45%.

@@ Coverage Diff @@## master #894 +/- ##
==========================================
- Coverage 93.6% 93.57% -0.03% 
==========================================
Files 59 59 Lines 9769 9787 +18 ==========================================
+ Hits 9144 9158 +14 - Misses 625 629 +4

Impacted Files	Coverage Δ
git/repo/base.py	93.57% <95.45%> (-0.6%)	⬇️

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[Byron]

Thanks so much! I am glad you could find the time.
In the next days, GitPython 3 will be released and include the fix.