t: document 'test_must_fail ok=<signal-name>'

Since 'test_might_fail' is implemented as a thin wrapper around
'test_must_fail', it also accepts the same options.  Mention this in
the docs as well.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/README

@@ -658,7 +658,7 @@ library for your script to use.
 		test_expect_code 1 git merge "merge msg" B master
 	'
- - test_must_fail <git-command>
+ - test_must_fail [<options>] <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
@@ -666,11 +666,21 @@ library for your script to use.
    treats it as just another expected failure, which would let such a
    bug go unnoticed.
- - test_might_fail <git-command>
+   Accepts the following options:
+
+     ok=<signal-name>[,<...>]:
+       Don't treat an exit caused by the given signal as error.
+       Multiple signals can be specified as a comma separated list.
+       Currently recognized signal names are: sigpipe, success.
+       (Don't use 'success', use 'test_might_fail' instead.)
+
+ - test_might_fail [<options>] <git-command>
    Similar to test_must_fail, but tolerate success, too.  Use this
    instead of "<git-command> || :" to catch failures due to segv.
+   Accepts the same options as test_must_fail.
+
  - test_cmp <expected> <actual>
    Check whether the content of the <actual> file matches the

t/test-lib-functions.sh

@@ -610,6 +610,14 @@ list_contains () {
 #
 # Writing this as "! git checkout ../outerspace" is wrong, because
 # the failure could be due to a segv.  We want a controlled failure.
+#
+# Accepts the following options:
+#
+#   ok=<signal-name>[,<...>]:
+#     Don't treat an exit caused by the given signal as error.
+#     Multiple signals can be specified as a comma separated list.
+#     Currently recognized signal names are: sigpipe, success.
+#     (Don't use 'success', use 'test_might_fail' instead.)
 test_must_fail () {
 	case "$1" in
@@ -656,6 +664,8 @@ test_must_fail () {
 #
 # Writing "git config --unset all.configuration || :" would be wrong,
 # because we want to notice if it fails due to segv.
+#
+# Accepts the same options as test_must_fail.
 test_might_fail () {
 	test_must_fail ok=success "$@"