t/Makefile: run unit tests alongside shell tests

Add a wrapper script to allow `prove` to run both shell tests and unit
tests from a single invocation. This avoids issues around running prove
twice in CI, as discussed in [1].

Additionally, this moves the unit tests into the main dev workflow, so
that errors can be spotted more quickly. Accordingly, we remove the
separate unit tests step for Linux CI. (We leave the Windows CI
unit-test step as-is, because the sharding scheme there involves
selecting specific test files rather than running `make test`.)

[1] https://lore.kernel.org/git/pull.1613.git.1699894837844.gitgitgadget@gmail.com/

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

Author: peff

ci/run-build-and-tests.sh

@@ -50,8 +50,6 @@ if test -n "$run_tests"
 then
 	group "Run tests" make test ||
 	handle_failed_tests
-	group "Run unit tests" \
-		make DEFAULT_UNIT_TEST_TARGET=unit-tests-prove unit-tests
 fi
 check_unignored_build_artifacts
 

t/Makefile

@@ -68,7 +68,7 @@ failed:
 	test -z "$$failed" || $(MAKE) $$failed
 
 prove: pre-clean check-chainlint $(TEST_LINT)
-	@echo "*** prove ***"; $(CHAINLINTSUPPRESS) $(PROVE) --exec '$(TEST_SHELL_PATH_SQ)' $(GIT_PROVE_OPTS) $(T) :: $(GIT_TEST_OPTS)
+	@echo "*** prove (shell & unit tests) ***"; $(CHAINLINTSUPPRESS) TEST_SHELL_PATH='$(TEST_SHELL_PATH_SQ)' $(PROVE) --exec ./run-test.sh $(GIT_PROVE_OPTS) $(T) $(UNIT_TESTS) :: $(GIT_TEST_OPTS)
 	$(MAKE) clean-except-prove-cache
 
 $(T):

t/run-test.sh

@@ -0,0 +1,18 @@
+#!/bin/sh
+
+# A simple wrapper to run shell tests via TEST_SHELL_PATH,
+# or exec unit tests directly.
+
+case "$1" in
+*.sh)
+	if test -z "${TEST_SHELL_PATH}"
+	then
+		echo >&2 "ERROR: TEST_SHELL_PATH is empty or not set"
+		exit 1
+	fi
+	exec "${TEST_SHELL_PATH}" "$@"
+	;;
+*)
+	exec "$@"
+	;;
+esac