Read, verify, and traverse git commit graphs.
A [commit graph][Graph] acts as a cache is a set of [graph files][file::File] each storing various commits in a way that accelerates lookups considerably compared to traversing the git history by usual means.
A [Graph] is generated as each [File][file::File] only contains a subset of all commits in the git commit
history to avoid having to recreate the entire cache each time the cache should be updated, thus avoiding to traverse
the git history that is already present in the [Graph].