Merge branch 'mk/grep-pcre'

* mk/grep-pcre:
  git-grep: Fix problems with recently added tests
  git-grep: Update tests (mainly for -P)
  Makefile: Pass USE_LIBPCRE down in GIT-BUILD-OPTIONS
  git-grep: update tests now regexp type is "last one wins"
  git-grep: do not die upon -F/-P when grep.extendedRegexp is set.
  git-grep: Bail out when -P is used with -F or -E
  grep: Add basic tests
  configure: Check for libpcre
  git-grep: Learn PCRE
  grep: Extract compile_regexp_failed() from compile_regexp()
  grep: Fix a typo in a comment
  grep: Put calls to fixmatch() and regmatch() into patmatch()
  contrib/completion: --line-number to git grep
  Documentation: Add --line-number to git-grep synopsis

contrib/completion/git-completion.bash

@@ -1441,8 +1441,9 @@ _git_grep ()
 		__gitcomp "
 			--cached
 			--text --ignore-case --word-regexp --invert-match
-			--full-name
+			--full-name --line-number
 			--extended-regexp --basic-regexp --fixed-strings
+			--perl-regexp
 			--files-with-matches --name-only
 			--files-without-match
 			--max-depth