t/README: clarify test_must_fail description

Some have found the wording of the description to be somewhat ambiguous
with respect to when it is desirable to use test_must_fail instead of
"! <git-command>".  Tweak the wording somewhat to hopefully clarify that
it is _because_ test_must_fail can detect segmentation fault that it is
desirable to use it instead of "! <git-command>".

Signed-off-by: Brandon Casey <casey@nrlssc.navy.mil>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/README b/t/README
index 0e4e8d8862c96383a6f6f22a1b6bb01044925620..fecb76e599cee2643e4f6c05c44fa2585e807284 100644 (file)
--- a/t/README
+++ b/t/README
@@ -275,6 +275,14 @@ library for your script to use.
    Merges the given rev using the given message.  Like test_commit,
    creates a tag and calls test_tick before committing.
 
+ - test_must_fail <git-command>
+
+   Run a git command and ensure it fails in a controlled way.  Use
+   this instead of "! <git-command>".  When git-command dies due to a
+   segfault, test_must_fail diagnoses it as an error; "! <git-command>"
+   treats it as just another expected failure, which would let such a
+   bug go unnoticed.
+
 Tips for Writing Tests
 ----------------------