Bug#774050: CVE-2014-9390

[Emmanuel Bourg]

Here are the relevant commits to backport:

Always ignore case when forbidding .git in ObjectChecker
https://github.com/eclipse/jgit/commit/07612a6

Disallow ".git." and ".git<space>"
https://github.com/eclipse/jgit/commit/10310bf

Disallow Windows shortname "GIT~1"
https://github.com/eclipse/jgit/commit/a09b1b6

Disallow names potentially mapping to ".git" on HFS+
https://github.com/eclipse/jgit/commit/d476d2f