Merge branch 'jc/grep-lookahead'

* jc/grep-lookahead: grep --no-index: allow use of "git grep" outside a git repository grep: prepare to run outside of a work tree grep: rip out pessimization to use fixmatch() grep: rip out support for external grep grep: optimize built-in grep by skipping lines that do not hit Conflicts: builtin-grep.c t/t7002-grep.sh