Merge pull request #301: Update 'git maintenance' to match upstream

This PR updates our `vfs-2.29.0` branch's version of `git maintenance` to match the latest in upstream. Unfortunately, not all of these commits made it to the `2.30` release candidate, but there are more commits from the series making it in. They will cause a conflict in the `vfs-2.30.0` rebase, so merge them in here. This also includes the `fixup!` reverts of the earlier versions.

Finally, I also noticed that we started depending on `git maintenance start` in Scalar for macOS, but we never checked that this worked with the shared object cache. It doesn't! 😨  The very tip commit of this PR includes logic to make `git maintenance run` care about `gvfs.sharedCache`. Functional test updates in Scalar will follow.

Author: derrickstolee

builtin/gc.c

@@ -1338,12 +1338,19 @@ static int write_loose_object_to_stdin(const struct object_id *oid,
 	return ++(d->count) > d->batch_size;
 }
 
+static const char *shared_object_dir = NULL;
+
 static int pack_loose(struct maintenance_run_opts *opts)
 {
 	struct repository *r = the_repository;
 	int result = 0;
 	struct write_loose_object_data data;
 	struct child_process pack_proc = CHILD_PROCESS_INIT;
+	const char *object_dir = r->objects->sources->path;
+
+	/* If set, use the shared object directory. */
+	if (shared_object_dir)
+		object_dir = shared_object_dir;
 
 	/*
 	 * Do not start pack-objects process
@@ -1361,7 +1368,7 @@ static int pack_loose(struct maintenance_run_opts *opts)
 		strvec_push(&pack_proc.args, "--quiet");
 	else
 		strvec_push(&pack_proc.args, "--no-quiet");
-	strvec_pushf(&pack_proc.args, "%s/pack/loose", r->objects->sources->path);
+	strvec_pushf(&pack_proc.args, "%s/pack/loose", object_dir);
 
 	pack_proc.in = -1;
 
@@ -1832,11 +1839,12 @@ static int task_option_parse(const struct option *opt,
 }
 
 static int maintenance_run(int argc, const char **argv, const char *prefix,
-			   struct repository *repo UNUSED)
+			   struct repository *repo)
 {
 	struct maintenance_run_opts opts = MAINTENANCE_RUN_OPTS_INIT;
 	struct string_list selected_tasks = STRING_LIST_INIT_DUP;
 	struct gc_config cfg = GC_CONFIG_INIT;
+	const char *tmp_obj_dir = NULL;
 	struct option builtin_maintenance_run_options[] = {
 		OPT_BOOL(0, "auto", &opts.auto_flag,
 			 N_("run tasks based on the state of the repository")),
@@ -1873,6 +1881,17 @@ static int maintenance_run(int argc, const char **argv, const char *prefix,
 		usage_with_options(builtin_maintenance_run_usage,
 				   builtin_maintenance_run_options);
 
+	/*
+	 * To enable the VFS for Git/Scalar shared object cache, use
+	 * the gvfs.sharedcache config option to redirect the
+	 * maintenance to that location.
+	 */
+	if (!repo_config_get_value(repo, "gvfs.sharedcache", &tmp_obj_dir) &&
+	    tmp_obj_dir) {
+		shared_object_dir = xstrdup(tmp_obj_dir);
+		setenv(DB_ENVIRONMENT, shared_object_dir, 1);
+	}
+
 	ret = maintenance_run_tasks(&opts, &cfg);
 
 	string_list_clear(&selected_tasks, 0);