Fix "git p4" when "--use-client-spec" and "--detect-branches" are
used together (the command used to misdetect branches).
* pw/p4-use-client-spec-branch-detection:
git p4: make branch detection work with --use-client-spec
git p4: do wildcard decoding in stripRepoPath
git p4: set self.branchPrefixes in initialization
git p4 test: add broken --use-client-spec --detect-branches tests
git p4 test: move client_view() function to library