Fix for issue #876

[s4v4g3]

Normalize path after joining submodule path and the relative path to the git dir, to eliminate path length errors on Windows

[codecov-io]

Codecov Report

Merging #877 into master will not change coverage.
The diff coverage is 100%.

@@ Coverage Diff @@## master #877 +/- ##
=======================================
Coverage 94.79% 94.79% =======================================
Files 59 59 Lines 9607 9607 =======================================
Hits 9107 9107 Misses 500 500

Impacted Files	Coverage Δ
git/repo/fun.py	92.55% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 11fd713...7cc1f08. Read the comment docs.

[jeking3]

There was an environmental error on the Windows python 2.7 job. Please amend --no-edit and force push your PR to kick another build. I would do it myself but only the owner of the AppVeyor account can do that.