[RFC/PATCH 3/4v2] test-lib: provide lazy TIME_COMMAND prereq

[Michael J Gruber <git@drmicha.warpmail.net>]

Some test want to use the time command (not the shell builtin) and test
for its availability at /usr/bin/time.

Provide a lazy prereq TIME_COMMAND which tests for $TEST_COMMAND_PATH,
which can be set from config.mak. It defaults to /usr/bin/time.

Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
---
Here's what the make variable version could look like.
1/4 and 4/4 would stay as is, 2/4 could be dropped.

 t/Makefile    | 5 +++--
 t/test-lib.sh | 4 ++++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/t/Makefile b/t/Makefile
index 88e289f..52b4039 100644
--- a/t/Makefile
+++ b/t/Makefile
@@ -13,6 +13,7 @@ TAR ?= $(TAR)
 RM ?= rm -f
 PROVE ?= prove
 DEFAULT_TEST_TARGET ?= test
+TIME_COMMAND_PATH ?= /usr/bin/time
 
 # Shell quote;
 SHELL_PATH_SQ = $(subst ','\'',$(SHELL_PATH))
@@ -27,11 +28,11 @@ test: pre-clean $(TEST_LINT)
 	$(MAKE) aggregate-results-and-cleanup
 
 prove: pre-clean $(TEST_LINT)
-	@echo "*** prove ***"; GIT_CONFIG=.git/config $(PROVE) --exec '$(SHELL_PATH_SQ)' $(GIT_PROVE_OPTS) $(T) :: $(GIT_TEST_OPTS)
+	@echo "*** prove ***"; GIT_CONFIG=.git/config TIME_COMMAND_PATH=$(TIME_COMMAND_PATH) $(PROVE) --exec '$(SHELL_PATH_SQ)' $(GIT_PROVE_OPTS) $(T) :: $(GIT_TEST_OPTS)
 	$(MAKE) clean-except-prove-cache
 
 $(T):
-	@echo "*** $@ ***"; GIT_CONFIG=.git/config '$(SHELL_PATH_SQ)' $@ $(GIT_TEST_OPTS)
+	@echo "*** $@ ***"; GIT_CONFIG=.git/config TIME_COMMAND_PATH=$(TIME_COMMAND_PATH) '$(SHELL_PATH_SQ)' $@ $(GIT_TEST_OPTS)
 
 pre-clean:
 	$(RM) -r test-results
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 489bc80..173eb13 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -738,6 +738,10 @@ test_lazy_prereq UTF8_NFD_TO_NFC '
 	esac
 '
 
+test_lazy_prereq TIME_COMMAND '
+	test -x "$TIME_COMMAND_PATH"
+'
+
 # When the tests are run as root, permission tests will report that
 # things are writable when they shouldn't be.
 test -w / || test_set_prereq SANITY
-- 
1.8.0.rc2.304.g9f3ac5c