test-tool run-command testsuite: support unit tests

Teach the testsuite runner in `test-tool run-command testsuite` how to
run unit tests: if TEST_SHELL_PATH is not set, run the programs directly
from CWD, rather than defaulting to "sh" as an interpreter.

With this change, you can now use test-tool to run the unit tests:
$ make
$ cd t/unit-tests/bin
$ ../../helper/test-tool run-command testsuite

This should be helpful on Windows to allow running tests without
requiring Perl (for `prove`), as discussed in [1] and [2].

This again breaks backwards compatibility, as it is now required to set
TEST_SHELL_PATH properly for executing shell scripts, but again, as
noted in [2], there are no longer any such invocations in our codebase.

[1] https://lore.kernel.org/git/[email protected]/
[2] https://lore.kernel.org/git/[email protected]/

Signed-off-by: Josh Steadmon <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: steadmon

t/helper/test-run-command.c

@@ -158,16 +158,22 @@ static int testsuite(int argc, const char **argv)
 		.task_finished = test_finished,
 		.data = &suite,
 	};
+	struct strbuf progpath = STRBUF_INIT;
+	size_t path_prefix_len;
 
 	argc = parse_options(argc, argv, NULL, options,
 			testsuite_usage, PARSE_OPT_STOP_AT_NON_OPTION);
 
 	if (max_jobs <= 0)
 		max_jobs = online_cpus();
 
+	/*
+	 * If we run without a shell, execute the programs directly from CWD.
+	 */
 	suite.shell_path = getenv("TEST_SHELL_PATH");
 	if (!suite.shell_path)
-		suite.shell_path = "sh";
+		strbuf_addstr(&progpath, "./");
+	path_prefix_len = progpath.len;
 
 	dir = opendir(".");
 	if (!dir)
@@ -180,13 +186,17 @@ static int testsuite(int argc, const char **argv)
 
 		/* No pattern: match all */
 		if (!argc) {
-			string_list_append(&suite.tests, p);
+			strbuf_setlen(&progpath, path_prefix_len);
+			strbuf_addstr(&progpath, p);
+			string_list_append(&suite.tests, progpath.buf);
 			continue;
 		}
 
 		for (i = 0; i < argc; i++)
 			if (!wildmatch(argv[i], p, 0)) {
-				string_list_append(&suite.tests, p);
+				strbuf_setlen(&progpath, path_prefix_len);
+				strbuf_addstr(&progpath, p);
+				string_list_append(&suite.tests, progpath.buf);
 				break;
 			}
 	}
@@ -213,6 +223,7 @@ static int testsuite(int argc, const char **argv)
 
 	string_list_clear(&suite.tests, 0);
 	string_list_clear(&suite.failed, 0);
+	strbuf_release(&progpath);
 
 	return ret;
 }