Ensure we hide configured commits

[epage]

Users are able to hide specific commits from blame. I'm guessing git2 isn't doing that for us and we'll need to implement it ourselves.

[epage]

https://git-scm.com/docs/git-config#Documentation/git-config.txt-blameignoreRevsFile

Ignore revisions listed in the file, one unabbreviated object name per line, in git-blame[1]. Whitespace and comments beginning with # are ignored. This option may be repeated multiple times. Empty file names will reset the list of ignored revisions. This option will be handled before the command line option --ignore-revs-file.

[epage]

Huh, not seeing support for this in git2. Unless its a feature we have to implement on top somehow (e.g. checking the Oid and doing a second blame), I'm assuming the best we can do is to just mark the line as unblameable.