Problem: filetype: .git-blame-ignore-revs file is not recognized
Solution: Detect .git-blame-ignore-revs file as gitrevlist filetype,
include syntax and filetype plugins (Fionn Fitzmaurice)
A Git revision list is
> a list of object names (i.e. one unabbreviated SHA-1 per line)...,
> comments (#), empty lines, and any leading and trailing whitespace are
> ignored.
(from Git's fsck.skipList documentation).
The default output of git rev-list will match this. It is also suitable
as input to git blame --ignore-revs-file.
This adds filetype detection matching .git-blame-ignore-revs files,
syntax highlighting and basic filetype settings.
closes: vim/vim#20702a8d5be9284
Co-authored-by: Fionn Fitzmaurice <fionn@github.com>
