t/Makefile: introduce TEST_SHELL_PATHjk/test-suite-tracing

You may want to run the test suite with a different shell
than you use to build Git. For instance, you may build with
SHELL_PATH=/bin/sh (because it's faster, or it's what you
expect to exist on systems where the build will be used) but
want to run the test suite with bash (e.g., since that
allows using "-x" reliably across the whole test suite).
There's currently no good way to do this.

You might think that doing two separate make invocations,
like:

  make &&
  make -C t SHELL_PATH=/bin/bash

would work. And it _almost_ does. The second make will see
our bash SHELL_PATH, and we'll use that to run the
individual test scripts (or tell prove to use it to do so).
So far so good.

But this breaks down when "--tee" or "--verbose-log" is
used. Those options cause the test script to actually
re-exec itself using $SHELL_PATH. But wait, wouldn't our
second make invocation have set SHELL_PATH correctly in the
environment?

Yes, but test-lib.sh sources GIT-BUILD-OPTIONS, which we
built during the first "make". And that overrides the
environment, giving us the original SHELL_PATH again.

Let's introduce a new variable that lets you specify a
specific shell to be run for the test scripts. Note that we
have to touch both the main and t/ Makefiles, since we have
to record it in GIT-BUILD-OPTIONS in one, and use it in the
latter.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

3 files changed, 13 insertions, 3 deletions

diff --git a/Makefile b/Makefile
index ee9d5eb11e..ed96453b5c 100644
--- a/Makefile
+++ b/Makefile
@@ -425,6 +425,10 @@ all::
 #
 # to say "export LESS=FRX (and LV=-c) if the environment variable
 # LESS (and LV) is not set, respectively".
+#
+# Define TEST_SHELL_PATH if you want to use a shell besides SHELL_PATH for
+# running the test scripts (e.g., bash has better support for "set -x"
+# tracing).
 
 GIT-VERSION-FILE: FORCE
 	@$(SHELL_PATH) ./GIT-VERSION-GEN
@@ -727,6 +731,8 @@ endif
 export PERL_PATH
 export PYTHON_PATH
 
+TEST_SHELL_PATH = $(SHELL_PATH)
+
 LIB_FILE = libgit.a
 XDIFF_LIB = xdiff/lib.a
 VCSSVN_LIB = vcs-svn/lib.a
@@ -1721,6 +1727,7 @@ prefix_SQ = $(subst ','\'',$(prefix))
 gitwebdir_SQ = $(subst ','\'',$(gitwebdir))
 
 SHELL_PATH_SQ = $(subst ','\'',$(SHELL_PATH))
+TEST_SHELL_PATH_SQ = $(subst ','\'',$(TEST_SHELL_PATH))
 PERL_PATH_SQ = $(subst ','\'',$(PERL_PATH))
 PYTHON_PATH_SQ = $(subst ','\'',$(PYTHON_PATH))
 TCLTK_PATH_SQ = $(subst ','\'',$(TCLTK_PATH))
@@ -2351,6 +2358,7 @@ GIT-LDFLAGS: FORCE
 # and the first level quoting from the shell that runs "echo".
 GIT-BUILD-OPTIONS: FORCE
 	@echo SHELL_PATH=\''$(subst ','\'',$(SHELL_PATH_SQ))'\' >$@+
+	@echo TEST_SHELL_PATH=\''$(subst ','\'',$(TEST_SHELL_PATH_SQ))'\' >>$@+
 	@echo PERL_PATH=\''$(subst ','\'',$(PERL_PATH_SQ))'\' >>$@+
 	@echo DIFF=\''$(subst ','\'',$(subst ','\'',$(DIFF)))'\' >>$@+
 	@echo PYTHON_PATH=\''$(subst ','\'',$(PYTHON_PATH_SQ))'\' >>$@+
diff --git a/t/Makefile b/t/Makefile
index 1bb06c36f2..96317a35f4 100644
--- a/t/Makefile
+++ b/t/Makefile
@@ -8,6 +8,7 @@
 
 #GIT_TEST_OPTS = --verbose --debug
 SHELL_PATH ?= $(SHELL)
+TEST_SHELL_PATH ?= $(SHELL_PATH)
 PERL_PATH ?= /usr/bin/perl
 TAR ?= $(TAR)
 RM ?= rm -f
@@ -23,6 +24,7 @@ endif
 
 # Shell quote;
 SHELL_PATH_SQ = $(subst ','\'',$(SHELL_PATH))
+TEST_SHELL_PATH_SQ = $(subst ','\'',$(TEST_SHELL_PATH))
 PERL_PATH_SQ = $(subst ','\'',$(PERL_PATH))
 TEST_RESULTS_DIRECTORY_SQ = $(subst ','\'',$(TEST_RESULTS_DIRECTORY))
 
@@ -42,11 +44,11 @@ failed:
 	test -z "$$failed" || $(MAKE) $$failed
 
 prove: pre-clean $(TEST_LINT)
-	@echo "*** prove ***"; $(PROVE) --exec '$(SHELL_PATH_SQ)' $(GIT_PROVE_OPTS) $(T) :: $(GIT_TEST_OPTS)
+	@echo "*** prove ***"; $(PROVE) --exec '$(TEST_SHELL_PATH_SQ)' $(GIT_PROVE_OPTS) $(T) :: $(GIT_TEST_OPTS)
 	$(MAKE) clean-except-prove-cache
 
 $(T):
-	@echo "*** $@ ***"; '$(SHELL_PATH_SQ)' $@ $(GIT_TEST_OPTS)
+	@echo "*** $@ ***"; '$(TEST_SHELL_PATH_SQ)' $@ $(GIT_TEST_OPTS)
 
 pre-clean:
 	$(RM) -r '$(TEST_RESULTS_DIRECTORY_SQ)'
diff --git a/t/test-lib.sh b/t/test-lib.sh
index b8dd5e79ac..1ae0fc02d0 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -80,7 +80,7 @@ done,*)
 	# from any previous runs.
 	>"$GIT_TEST_TEE_OUTPUT_FILE"
 
-	(GIT_TEST_TEE_STARTED=done ${SHELL_PATH} "$0" "$@" 2>&1;
+	(GIT_TEST_TEE_STARTED=done ${TEST_SHELL_PATH} "$0" "$@" 2>&1;
 	 echo $? >"$BASE.exit") | tee -a "$GIT_TEST_TEE_OUTPUT_FILE"
 	test "$(cat "$BASE.exit")" = 0
 	exit