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-rerere.c

@@ -6,7 +6,7 @@
 #include "xdiff-interface.h"
 
 static const char git_rerere_usage[] =
-"git-rerere [clear | status | diff | gc]";
+"git rerere [clear | status | diff | gc]";
 
 /* these values are days */
 static int cutoff_noresolve = 15;