Merge branch 'jk/grep-no-index-fix' into maint

The code to parse the command line "git grep <patterns>... <rev> [[--] <pathspec>...]" has been cleaned up, and a handful of bugs have been fixed (e.g. we used to check "--" if it is a rev). * jk/grep-no-index-fix: grep: treat revs the same for --untracked as for --no-index grep: do not diagnose misspelt revs with --no-index grep: avoid resolving revision names in --no-index case grep: fix "--" rev/pathspec disambiguation grep: re-order rev-parsing loop grep: do not unnecessarily query repo for "--" grep: move thread initialization a little lower