test-lib: valgrind for only tests matching a pattern

With the new --valgrind-only=<pattern> option, one can enable
--valgrind at a per-test granularity, exactly analogous to
--verbose-only from the previous commit.

The options are wired such that --valgrind implies --verbose (as
before), but --valgrind-only=<pattern> implies
--verbose-only=<pattern> unless --verbose is also in effect.

Signed-off-by: Thomas Rast <trast@inf.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 95df832..e9f3294 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -201,6 +201,9 @@
 	--valgrind=*)
 		valgrind=$(expr "z$1" : 'z[^=]*=\(.*\)')
 		shift ;;
+	--valgrind-only=*)
+		valgrind_only=$(expr "z$1" : 'z[^=]*=\(.*\)')
+		shift ;;
 	--tee)
 		shift ;; # was handled already
 	--root=*)
@@ -211,7 +214,14 @@
 	esac
 done
 
-test -n "$valgrind" && verbose=t
+if test -n "$valgrind_only"
+then
+	test -z "$valgrind" && valgrind=memcheck
+	test -z "$verbose" && verbose_only="$valgrind_only"
+elif test -n "$valgrind"
+then
+	verbose=t
+fi
 
 if test -n "$color"
 then
@@ -371,6 +381,25 @@
 	last_verbose=$verbose
 }
 
+maybe_teardown_valgrind () {
+	test -z "$GIT_VALGRIND" && return
+	GIT_VALGRIND_ENABLED=
+}
+
+maybe_setup_valgrind () {
+	test -z "$GIT_VALGRIND" && return
+	if test -z "$valgrind_only"
+	then
+		GIT_VALGRIND_ENABLED=t
+		return
+	fi
+	GIT_VALGRIND_ENABLED=
+	if match_pattern_list $test_count $valgrind_only
+	then
+		GIT_VALGRIND_ENABLED=t
+	fi
+}
+
 test_eval_ () {
 	# This is a separate function because some tests use
 	# "return" to end a test_expect_success block early.
@@ -401,10 +430,12 @@
 test_start_ () {
 	test_count=$(($test_count+1))
 	maybe_setup_verbose
+	maybe_setup_valgrind
 }
 
 test_finish_ () {
 	echo >&3 ""
+	maybe_teardown_valgrind
 	maybe_teardown_verbose
 }
 
@@ -590,6 +621,9 @@
 	export GIT_VALGRIND
 	GIT_VALGRIND_MODE="$valgrind"
 	export GIT_VALGRIND_MODE
+	GIT_VALGRIND_ENABLED=t
+	test -n "$valgrind_only" && GIT_VALGRIND_ENABLED=
+	export GIT_VALGRIND_ENABLED
 elif test -n "$GIT_TEST_INSTALLED"
 then
 	GIT_EXEC_PATH=$($GIT_TEST_INSTALLED/git --exec-path)  ||