RFR: 868: Skara should ignore .gitconfig and /etc/gitconfig [v3]

[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.

Magnus Ihse Bursie has updated the pull request incrementally with one additional commit since the last revision:

  Add unit test to verify that we block user/system configs.

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Changes:
  - all: https://git.openjdk.java.net/skara/pull/997/files
  - new: https://git.openjdk.java.net/skara/pull/997/files/d7a13059..96e82612

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=skara&pr=997&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=skara&pr=997&range=01-02

  Stats: 55 lines in 3 files changed: 45 ins; 3 del; 7 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