Merge branch 'tr/test-v-and-v-subtest-only'

Allows N instances of tests run in parallel, each running 1/N parts
of the test suite under Valgrind, to speed things up.

* tr/test-v-and-v-subtest-only:
  perf-lib: fix start/stop of perf tests
  test-lib: support running tests under valgrind in parallel
  test-lib: allow prefixing a custom string before "ok N" etc.
  test-lib: valgrind for only tests matching a pattern
  test-lib: verbose mode for only tests matching a pattern
  test-lib: self-test that --verbose works
  test-lib: rearrange start/end of test_expect_* and test_skip
  test-lib: refactor $GIT_SKIP_TESTS matching
  test-lib: enable MALLOC_* for the actual tests

t/test-lib-functions.sh

@@ -343,6 +343,7 @@ test_declared_prereq () {
 }
 
 test_expect_failure () {
+	test_start_
 	test "$#" = 3 && { test_prereq=$1; shift; } || test_prereq=
 	test "$#" = 2 ||
 	error "bug in the test script: not 2 or 3 parameters to test-expect-failure"
@@ -357,10 +358,11 @@ test_expect_failure () {
 			test_known_broken_failure_ "$1"
 		fi
 	fi
-	echo >&3 ""
+	test_finish_
 }
 
 test_expect_success () {
+	test_start_
 	test "$#" = 3 && { test_prereq=$1; shift; } || test_prereq=
 	test "$#" = 2 ||
 	error "bug in the test script: not 2 or 3 parameters to test-expect-success"
@@ -375,7 +377,7 @@ test_expect_success () {
 			test_failure_ "$@"
 		fi
 	fi
-	echo >&3 ""
+	test_finish_
 }
 
 # test_external runs external test scripts that provide continuous