rev-parse: let some options run outside repository

Once upon a time, you could use "--local-env-vars" and
"--resolve-git-dir" outside of any git repository, but they
had to come first on the command line. Commit 68889b4
(rev-parse: remove restrictions on some options, 2013-07-21)
put them into the normal option-parsing loop, fixing the
latter. But it inadvertently broke the former, as we call
setup_git_directory() before starting that loop.

We can note that those options don't care even conditionally
about whether we are in a git repo. So it's fine if we
simply wait to setup the repo until we see an option that
needs it.

However, there is one special exception we should make:
historically, rev-parse will set up the repository and read
config even if there are _no_ options. Some of the
tests in t1300 rely on this to check "git -c $config"
parsing. That's not mirroring real-world use, and we could
tweak the test.  But t0002 uses a bare "git rev-parse" to
check "are we in a git repository?". It's plausible that
real-world scripts are relying on this.

So let's cover this case specially, and treat an option-less
"rev-parse" as "see if we're in a repo".

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

Author: peff

builtin/rev-parse.c

@@ -505,6 +505,7 @@ N_("git rev-parse --parseopt [<options>] -- [<args>...]\n"
 int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 {
 	int i, as_is = 0, verify = 0, quiet = 0, revs_count = 0, type = 0;
+	int did_repo_setup = 0;
 	int has_dashdash = 0;
 	int output_prefix = 0;
 	unsigned char sha1[20];
@@ -528,11 +529,40 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 		}
 	}
 
-	prefix = setup_git_directory();
-	git_config(git_default_config, NULL);
+	/* No options; just report on whether we're in a git repo or not. */
+	if (argc == 1) {
+		setup_git_directory();
+		git_config(git_default_config, NULL);
+		return 0;
+	}
+
 	for (i = 1; i < argc; i++) {
 		const char *arg = argv[i];
 
+		if (!strcmp(arg, "--local-env-vars")) {
+			int i;
+			for (i = 0; local_repo_env[i]; i++)
+				printf("%s\n", local_repo_env[i]);
+			continue;
+		}
+		if (!strcmp(arg, "--resolve-git-dir")) {
+			const char *gitdir = argv[++i];
+			if (!gitdir)
+				die("--resolve-git-dir requires an argument");
+			gitdir = resolve_gitdir(gitdir);
+			if (!gitdir)
+				die("not a gitdir '%s'", argv[i]);
+			puts(gitdir);
+			continue;
+		}
+
+		/* The rest of the options require a git repository. */
+		if (!did_repo_setup) {
+			prefix = setup_git_directory();
+			git_config(git_default_config, NULL);
+			did_repo_setup = 1;
+		}
+
 		if (!strcmp(arg, "--git-path")) {
 			if (!argv[i + 1])
 				die("--git-path requires an argument");
@@ -706,12 +736,6 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 				add_ref_exclusion(&ref_excludes, arg + 10);
 				continue;
 			}
-			if (!strcmp(arg, "--local-env-vars")) {
-				int i;
-				for (i = 0; local_repo_env[i]; i++)
-					printf("%s\n", local_repo_env[i]);
-				continue;
-			}
 			if (!strcmp(arg, "--show-toplevel")) {
 				const char *work_tree = get_git_work_tree();
 				if (work_tree)
@@ -766,16 +790,6 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 				puts(get_git_common_dir());
 				continue;
 			}
-			if (!strcmp(arg, "--resolve-git-dir")) {
-				const char *gitdir = argv[++i];
-				if (!gitdir)
-					die("--resolve-git-dir requires an argument");
-				gitdir = resolve_gitdir(gitdir);
-				if (!gitdir)
-					die("not a gitdir '%s'", argv[i]);
-				puts(gitdir);
-				continue;
-			}
 			if (!strcmp(arg, "--is-inside-git-dir")) {
 				printf("%s\n", is_inside_git_dir() ? "true"
 						: "false");

t/t1515-rev-parse-outside-repo.sh

@@ -27,14 +27,14 @@ test_expect_success 'rev-parse --sq-quote' '
 	test_cmp expect actual
 '
 
-test_expect_failure 'rev-parse --local-env-vars' '
+test_expect_success 'rev-parse --local-env-vars' '
 	git rev-parse --local-env-vars >actual &&
 	# we do not want to depend on the complete list here,
 	# so just look for something plausible
 	grep ^GIT_DIR actual
 '
 
-test_expect_failure 'rev-parse --resolve-git-dir' '
+test_expect_success 'rev-parse --resolve-git-dir' '
 	git init --separate-git-dir repo dir &&
 	test_must_fail git rev-parse --resolve-git-dir . &&
 	echo "$(pwd)/repo" >expect &&