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. Add tests that carefully check a
few of these environment variables, including GIT_CONFIG_GLOBAL and
GIT_CONFIG_PARAMETERS as examples. These tests do not provide full
coverage, but cover enough to prevent a bug that existed in an earlier
version of this change.

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 +16,31 @@ 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:
+		 * - GIT_CONFIG, GIT_CONFIG_GLOBAL, and GIT_CONFIG_SYSTEM
+		 *   point Git at different file locations for these scopes.
+		 * - GIT_CONFIG_PARAMETERS, and GIT_CONFIG_COUNT 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 (!starts_with(local_repo_env[i], "GIT_CONFIG") &&
+		    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

@@ -8,10 +8,12 @@ TEST_NO_CREATE_REPO=1
 . ./test-lib.sh
 
 test_expect_success 'run based on configured value' '
-	git init one &&
-	git init two &&
-	git init three &&
-	git init ~/four &&
+	git init --initial-branch=one one &&
+	git init --initial-branch=two two &&
+	git -C two worktree add --orphan ../three &&
+	git -C three checkout -b three &&
+	git init --initial-branch=four ~/four &&
+
 	git -C two commit --allow-empty -m "DID NOT RUN" &&
 	git config --global run.key "$TRASH_DIRECTORY/one" &&
 	git config --global --add run.key "$TRASH_DIRECTORY/three" &&
@@ -35,7 +37,43 @@ 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 &&
+	test_grep "ran from worktree" message &&
+	git -C two log -1 --pretty=format:%s >message &&
+	test_grep ! "ran from worktree" message &&
+	git -C three log -1 --pretty=format:%s >message &&
+	test_grep "ran from worktree" message &&
+	git -C ~/four log -1 --pretty=format:%s >message &&
+	test_grep "ran from worktree" message &&
+
+	# Test running with config values set by environment
+	cat >expect <<-EOF &&
+	ran from worktree (HEAD -> refs/heads/one)
+	ran from worktree (HEAD -> refs/heads/three)
+	ran from worktree (HEAD -> refs/heads/four)
+	EOF
+
+	GIT_CONFIG_PARAMETERS="${SQ}log.decorate=full${SQ}" \
+		git -C three for-each-repo --config=run.key -- log --format="%s%d" -1 >out &&
+	test_cmp expect out &&
+
+	cat >test-config <<-EOF &&
+	[run]
+		key = $(pwd)/one
+		key = $(pwd)/three
+		key = $(pwd)/four
+
+	[log]
+		decorate = full
+	EOF
+
+	GIT_CONFIG_GLOBAL="$(pwd)/test-config" \
+		git -C three for-each-repo --config=run.key -- log --format="%s%d" -1 >out &&
+	test_cmp expect out
 '
 
 test_expect_success 'do nothing on empty config' '