Add GIT_BLAME_USE_MAILMAP flag (#676)
Add GIT_BLAME_USE_MAILMAP flag (#676)

The `GIT_BLAME_USE_MAILMAP` blame option flag was introduced in libgit2 v0.28

Change type: #minor
clns/git2go,libgit2/git2go,clns/git2go,libgit2/git2go,clns/git2go,libgit2/git2go