Add -F to commit search to treat keywords as strings (#28744) (#28748)

Add -F to commit search to treat keywords as strings (#28744) (#28748)

Backport #28744 by @me-heer

Fixes #28269

The [default
behavior](https://git-scm.com/docs/git-log#Documentation/git-log.txt---basic-regexp)
of --grep in git log is to interpret the keyword as a regular
expression. This causes the search to fail in the cases where the search
keyword contains a `[`, since `[` is a special character used in grep.

If we want our keywords to be interpreted as 'strings', we should use
[-F
flag](https://git-scm.com/docs/git-log#Documentation/git-log.txt---basic-regexp).

Co-authored-by: Mihir Joshi <mihir67mj@gmail.com>