Simplify Proxy.git_commit_create() implementation
Reintroduce obsolete method to avoid breaking change
Rename Filter into CommitFilter
Rename GitSortOptions into CommitSortStrategies
Rename StashOptions into StashModifiers
Rename DiffOptions into DiffModifiers
Rename CheckoutOptions into CheckoutModifiers
Standardize comments style
Cleanup usings
Make build.libgit2sharp.sh executable
Favor Constants.Signature over BaseFixture.DummySignature
Make RelWithDebInfo the default libgit2 build flavor
Refactor Travis build script
Make Stash expose Base, Index and Untracked commits
Update libgit2 binaries to bd67979

https://github.com/libgit2/libgit2/compare/9d9fff3...bd67979
Teach UpdateLibgit2ToSha.ps1 to take arbitrary libgit2 library name.
Update UniqueIdentifer.targets to be called from arbitrary directory