Merge branch 'rs/maint-grep-F' into maint

"git grep -e '$pattern'", unlike the case where the patterns are read from a file, did not treat individual lines in the given pattern argument as separate regular expressions as it should. By René Scharfe * rs/maint-grep-F: grep: stop leaking line strings with -f grep: support newline separated pattern list grep: factor out do_append_grep_pat() grep: factor out create_grep_pat()