for-each-repo: work correctly in a worktree

When run in a worktree, the GIT_DIR directory is set in a different way
than in a typical repository. Show this by updating t0068 to include a
worktree and add a test that runs from that worktree. This requires
moving the repo.key config into a global config instead of the base test
repository's local config (demonstrating that it worked with
non-worktree Git repositories).

We need to be careful to unset the local Git environment variables and
let the child process rediscover them, while also reinstating those
variables in the parent process afterwards. Update run_command_on_repo()
to store, unset, then reset the non-NULL variables. But...

...we also need to be careful to not un-set environment variables around
-c config options or --no-replace-objects. A detailed comment includes
the justification for these filters.

Reported-by: Matthew Gabeler-Lee <fastcat@gmail.com>
Signed-off-by: Derrick Stolee <stolee@gmail.com>

Author: derrickstolee

builtin/for-each-repo.c

@@ -2,6 +2,7 @@
 
 #include "builtin.h"
 #include "config.h"
+#include "environment.h"
 #include "gettext.h"
 #include "parse-options.h"
 #include "path.h"
@@ -15,10 +16,29 @@ static const char * const for_each_repo_usage[] = {
 
 static int run_command_on_repo(const char *path, int argc, const char ** argv)
 {
-	int i;
+	int i = 0;
 	struct child_process child = CHILD_PROCESS_INIT;
 	char *abspath = interpolate_path(path, 0);
 
+	while (local_repo_env[i]) {
+		/*
+		 * Preserve pre-builtin options:
+		 * - CONFIG_ENVIRONMENT, CONFIG_DATA_ENVIRONMENT, and
+		 *   CONFIG_COUNT_ENVIRONMENT persist -c <name>=<value>
+		 *   and --config-env=<name>=<envvar> options.
+		 * - NO_REPLACE_OBJECTS_ENVIRONMENT persists the
+		 *   --no-replace-objects option.
+		 *
+		 * Note that the following options are not in local_repo_env:
+		 * - EXEC_PATH_ENVIRONMENT persists --exec-path option.
+		 */
+		if (strncmp(local_repo_env[i], "CONFIG_", 7) &&
+		    strcmp(local_repo_env[i], NO_REPLACE_OBJECTS_ENVIRONMENT))
+			strvec_push(&child.env, local_repo_env[i]);
+
+		i++;
+	}
+
 	child.git_cmd = 1;
 	strvec_pushl(&child.args, "-C", abspath, NULL);
 

t/t0068-for-each-repo.sh

@@ -10,7 +10,7 @@ TEST_NO_CREATE_REPO=1
 test_expect_success 'run based on configured value' '
 	git init one &&
 	git init two &&
-	git init three &&
+	git -C two worktree add --orphan ../three &&
 	git init ~/four &&
 	git -C two commit --allow-empty -m "DID NOT RUN" &&
 	git config --global run.key "$TRASH_DIRECTORY/one" &&
@@ -35,7 +35,17 @@ test_expect_success 'run based on configured value' '
 	git -C three log -1 --pretty=format:%s >message &&
 	grep again message &&
 	git -C ~/four log -1 --pretty=format:%s >message &&
-	grep again message
+	grep again message &&
+
+	git -C three for-each-repo --config=run.key -- commit --allow-empty -m "ran from worktree" &&
+	git -C one log -1 --pretty=format:%s >message &&
+	grep worktree message &&
+	git -C two log -1 --pretty=format:%s >message &&
+	! grep worktree message &&
+	git -C three log -1 --pretty=format:%s >message &&
+	grep worktree message &&
+	git -C ~/four log -1 --pretty=format:%s >message &&
+	grep worktree message
 '
 
 test_expect_success 'do nothing on empty config' '