Add another commit to .git-blame-ignore-revs

git-blame-ignore-revs: OptionalObsoleteFiles.inc sorting commits

Add sorting commits. This causes (suitably configured) git blame to
ignore the moving of blocks, correcting the associated commit for ~300
lines.

Reviewed by: emaste
Differential Revision: https://reviews.freebsd.org/D42602

Sort .git-blame-ignore-revs by commit order

This makes it easier to add blocks of commits such as
4ca5df80393e1f2..c90d0600ee000e78 which do a single thing over the
course of multiple commits. Sorting by hash would require manually
inserting each one with a comment.

Reviewed by: emaste
Differential Revision: https://reviews.freebsd.org/D42601

Add git-blame ignore file

.git-blame-ignore-revs lists commit hashes that should be skipped by
`git blame` e.g. non-functional whitespace or style cleanup.

The file is populated with a few sample entries.

Reviewed by: brooks, imp
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D36525

fixup ignore revs