Merge branch 'sb/dashless'

* sb/dashless:
  Make usage strings dash-less
  t/: Use "test_must_fail git" instead of "! git"
  t/test-lib.sh: exit with small negagive int is ok with test_must_fail

Conflicts:
	builtin-blame.c
	builtin-mailinfo.c
	builtin-mailsplit.c
	builtin-shortlog.c
	git-am.sh
	t/t4150-am.sh
	t/t4200-rerere.sh

builtin-grep.c

@@ -498,7 +498,7 @@ static int grep_object(struct grep_opt *opt, const char **paths,
 }
 
 static const char builtin_grep_usage[] =
-"git-grep <option>* <rev>* [-e] <pattern> [<path>...]";
+"git grep <option>* <rev>* [-e] <pattern> [<path>...]";
 
 static const char emsg_invalid_context_len[] =
 "%s: invalid context length argument";