RFR: 868: Skara should ignore .gitconfig and /etc/gitconfig

[Magnus Ihse Bursie]

Skara is already ignoring .hgrc for mercurial, but the corresponding solution for git was never put in place.

I also fixed a problem where an error condition would cause an infinite loop, which I ran into during testing.

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Commit messages:
 - 868: Skara should ignore .gitconfig and /etc/gitconfig

Changes: https://git.openjdk.java.net/skara/pull/997/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=997&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-868
  Stats: 48 lines in 5 files changed: 40 ins; 0 del; 8 mod
  Patch: https://git.openjdk.java.net/skara/pull/997.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/997/head:pull/997

PR: https://git.openjdk.java.net/skara/pull/997