[PATCH 00/15] [RFC] Upstreaming the Scalar command

@@ -198,12 +198,12 @@ static int set_recommended_config(void)
 	return 0;
 }
 
-static int start_maintenance(void)
+static int toggle_maintenance(int enable)
 {
-	return run_git("maintenance", "start", NULL);
+	return run_git("maintenance", enable ? "start" : "unregister", NULL);
 }
 
-static int add_enlistment(void)
+static int add_or_remove_enlistment(int add)
 {
 	int res;
 

@@ -214,24 +214,39 @@ static int add_enlistment(void)
 		      "scalar.repo", the_repository->worktree, NULL);
 
 	/*
-	 * If the setting is already there, then do nothing.
+	 * If we want to add and the setting is already there, then do nothing.
+	 * If we want to remove and the setting is not there, then do nothing.
 	 */
-	if (!res)
+	if ((add && !res) || (!add && res))
 		return 0;
 
-	return run_git("config", "--global", "--add",
+	return run_git("config", "--global", add ? "--add" : "--unset",
+		       add ? "--no-fixed-value" : "--fixed-value",
 		       "scalar.repo", the_repository->worktree, NULL);
 }
 
 static int register_dir(void)
 {
-	int res = add_enlistment();
+	int res = add_or_remove_enlistment(1);
 
 	if (!res)
 		res = set_recommended_config();
 
 	if (!res)
-		res = start_maintenance();
+		res = toggle_maintenance(1);
+
+	return res;
+}
+
+static int unregister_dir(void)
+{
+	int res = 0;
+
+	if (toggle_maintenance(0) < 0)
+		res = -1;
+
+	if (add_or_remove_enlistment(0) < 0)
+		res = -1;
 
 	return res;
 }

@@ -254,11 +269,30 @@ static int cmd_register(int argc, const char **argv)
 	return register_dir();
 }
 
+static int cmd_unregister(int argc, const char **argv)
+{
+	struct option options[] = {
+		OPT_END(),
+	};
+	const char * const usage[] = {
+		N_("scalar unregister [<enlistment>]"),
+		NULL
+	};
+
+	argc = parse_options(argc, argv, NULL, options,
+			     usage, 0);
+
+	setup_enlistment_directory(argc, argv, usage, options, NULL);
+
+	return unregister_dir();
+}
+
 static struct {
 	const char *name;
 	int (*fn)(int, const char **);
 } builtins[] = {
 	{ "register", cmd_register },
+	{ "unregister", cmd_unregister },
 	{ NULL, NULL},
 };
 

@@ -9,6 +9,7 @@ SYNOPSIS
 --------
 [verse]
 scalar register [<enlistment>]
+scalar unregister [<enlistment>]
 
 DESCRIPTION
 -----------

@@ -45,6 +46,13 @@ Note: when this subcommand is called in a worktree that is called `src/`, its
 parent directory is considered to be the Scalar enlistment. If the worktree is
 _not_ called `src/`, it itself will be considered to be the Scalar enlistment.
 
+Unregister
+~~~~~~~~~~
+
+unregister [<enlistment>]::
+	Remove the specified repository from the list of repositories
+	registered with Scalar and stop the scheduled background maintenance.
+
 SEE ALSO
 --------
 linkgit:git-maintenance[1].

@@ -7,6 +7,7 @@
 #include "parse-options.h"
 #include "config.h"
 #include "run-command.h"
+#include "refs.h"
 
 /*
  * Remove the deepest subdirectory in the provided path string. Path must not

@@ -251,6 +252,205 @@ static int unregister_dir(void)
 	return res;
 }
 
+/* printf-style interface, expects `<key>=<value>` argument */
+static int set_config(const char *fmt, ...)
+{
+	struct strbuf buf = STRBUF_INIT;
+	char *value;
+	int res;
+	va_list args;
+
+	va_start(args, fmt);
+	strbuf_vaddf(&buf, fmt, args);
+	va_end(args);
+
+	value = strchr(buf.buf, '=');
+	if (value)
+		*(value++) = '\0';
+	res = git_config_set_gently(buf.buf, value);
+	strbuf_release(&buf);
+
+	return res;
+}
+
+static char *remote_default_branch(const char *url)
+{
+	struct child_process cp = CHILD_PROCESS_INIT;
+	struct strbuf out = STRBUF_INIT;
+
+	cp.git_cmd = 1;
+	strvec_pushl(&cp.args, "ls-remote", "--symref", url, "HEAD", NULL);
+	if (!pipe_command(&cp, NULL, 0, &out, 0, NULL, 0)) {
+		const char *line = out.buf;
+
+		while (*line) {
+			const char *eol = strchrnul(line, '\n'), *p;
+			size_t len = eol - line;
+			char *branch;
+
+			if (!skip_prefix(line, "ref: ", &p) ||
+			    !strip_suffix_mem(line, &len, "\tHEAD")) {
+				line = eol + (*eol == '\n');
+				continue;
+			}
+
+			eol = line + len;
+			if (skip_prefix(p, "refs/heads/", &p)) {
+				branch = xstrndup(p, eol - p);
+				strbuf_release(&out);
+				return branch;
+			}
+
+			error(_("remote HEAD is not a branch: '%.*s'"),
+			      (int)(eol - p), p);
+			strbuf_release(&out);
+			return NULL;
+		}
+	}
+	warning(_("failed to get default branch name from remote; "
+		  "using local default"));
+	strbuf_reset(&out);
+
+	child_process_init(&cp);
+	cp.git_cmd = 1;
+	strvec_pushl(&cp.args, "symbolic-ref", "--short", "HEAD", NULL);
+	if (!pipe_command(&cp, NULL, 0, &out, 0, NULL, 0)) {
+		strbuf_trim(&out);
+		return strbuf_detach(&out, NULL);
+	}
+
+	strbuf_release(&out);
+	error(_("failed to get default branch name"));
+	return NULL;
+}
+
+static int cmd_clone(int argc, const char **argv)
+{
+	const char *branch = NULL;
+	int full_clone = 0;
+	struct option clone_options[] = {
+		OPT_STRING('b', "branch", &branch, N_("<branch>"),
+			   N_("branch to checkout after clone")),
+		OPT_BOOL(0, "full-clone", &full_clone,
+			 N_("when cloning, create full working directory")),
+		OPT_END(),
+	};
+	const char * const clone_usage[] = {
+		N_("scalar clone [<options>] [--] <repo> [<dir>]"),
+		NULL
+	};
+	const char *url;
+	char *enlistment = NULL, *dir = NULL;
+	struct strbuf buf = STRBUF_INIT;
+	int res;
+
+	argc = parse_options(argc, argv, NULL, clone_options, clone_usage, 0);
+
+	if (argc == 2) {
+		url = argv[0];
+		enlistment = xstrdup(argv[1]);
+	} else if (argc == 1) {
+		url = argv[0];
+
+		strbuf_addstr(&buf, url);
+		/* Strip trailing slashes, if any */
+		while (buf.len > 0 && is_dir_sep(buf.buf[buf.len - 1]))
+			strbuf_setlen(&buf, buf.len - 1);
+		/* Strip suffix `.git`, if any */
+		strbuf_strip_suffix(&buf, ".git");
+
+		enlistment = find_last_dir_sep(buf.buf);
+		if (!enlistment) {
+			die(_("cannot deduce worktree name from '%s'"), url);
+		}
+		enlistment = xstrdup(enlistment + 1);
+	} else {
+		usage_msg_opt(_("You must specify a repository to clone."),
+			      clone_usage, clone_options);
+	}
+
+	if (is_directory(enlistment))
+		die(_("directory '%s' exists already"), enlistment);
+
+	dir = xstrfmt("%s/src", enlistment);
+
+	strbuf_reset(&buf);
+	if (branch)
+		strbuf_addf(&buf, "init.defaultBranch=%s", branch);
+	else {
+		char *b = repo_default_branch_name(the_repository, 1);
+		strbuf_addf(&buf, "init.defaultBranch=%s", b);
+		free(b);
+	}
+
+	if ((res = run_git("-c", buf.buf, "init", "--", dir, NULL)))
+		goto cleanup;
+
+	if (chdir(dir) < 0) {
+		res = error_errno(_("could not switch to '%s'"), dir);
+		goto cleanup;
+	}
+
+	setup_git_directory();
+
+	/* common-main already logs `argv` */
+	trace2_def_repo(the_repository);
+
+	if (!branch && !(branch = remote_default_branch(url))) {
+		res = error(_("failed to get default branch for '%s'"), url);
+		goto cleanup;
+	}
+
+	if (set_config("remote.origin.url=%s", url) ||
+	    set_config("remote.origin.fetch="
+		       "+refs/heads/*:refs/remotes/origin/*") ||
+	    set_config("remote.origin.promisor=true") ||
+	    set_config("remote.origin.partialCloneFilter=blob:none")) {
+		res = error(_("could not configure remote in '%s'"), dir);
+		goto cleanup;
+	}
+
+	if (!full_clone &&
+	    (res = run_git("sparse-checkout", "init", "--cone", NULL)))
+		goto cleanup;
+
+	if (set_recommended_config())
+		return error(_("could not configure '%s'"), dir);
+
+	if ((res = run_git("fetch", "--quiet", "origin", NULL))) {
+		warning(_("partial clone failed; attempting full clone"));
+
+		if (set_config("remote.origin.promisor") ||
+		    set_config("remote.origin.partialCloneFilter")) {
+			res = error(_("could not configure for full clone"));
+			goto cleanup;
+		}
+
+		if ((res = run_git("fetch", "--quiet", "origin", NULL)))
+			goto cleanup;
+	}
+
+	if ((res = set_config("branch.%s.remote=origin", branch)))
+		goto cleanup;
+	if ((res = set_config("branch.%s.merge=refs/heads/%s",
+			      branch, branch)))
+		goto cleanup;
+
+	strbuf_reset(&buf);
+	strbuf_addf(&buf, "origin/%s", branch);
+	res = run_git("checkout", "-f", "-t", buf.buf, NULL);
+	if (res)
+		goto cleanup;
+
+	res = register_dir();
+
+cleanup:
+	free(enlistment);
+	free(dir);
+	strbuf_release(&buf);
+	return res;
+}
+
 static int cmd_list(int argc, const char **argv)
 {
 	if (argc != 1)

@@ -347,6 +547,7 @@ static struct {
 	const char *name;
 	int (*fn)(int, const char **);
 } builtins[] = {
+	{ "clone", cmd_clone },
 	{ "list", cmd_list },
 	{ "register", cmd_register },
 	{ "unregister", cmd_unregister },

@@ -8,6 +8,7 @@ scalar - an opinionated repository management tool
 SYNOPSIS
 --------
 [verse]
+scalar clone [--branch <main-branch>] [--full-clone] <url> [<enlistment>]
 scalar list
 scalar register [<enlistment>]
 scalar unregister [<enlistment>]

@@ -29,12 +30,37 @@ an existing Git worktree with Scalar whose name is not `src`, the enlistment
 will be identical to the worktree.
 
 The `scalar` command implements various subcommands, and different options
-depending on the subcommand. With the exception of `list`, all subcommands
-expect to be run in an enlistment.
+depending on the subcommand. With the exception of `clone` and `list`, all
+subcommands expect to be run in an enlistment.
 
 COMMANDS
 --------
 
+Clone
+~~~~~
+
+clone [<options>] <url> [<enlistment>]::
+	Clones the specified repository, similar to linkgit:git-clone[1]. By
+	default, only commit and tree objects are cloned. Once finished, the
+	worktree is located at `<enlistment>/src`.
++
+The sparse-checkout feature is enabled (except when run with `--full-clone`)
+and the only files present are those in the top-level directory. Use
+`git sparse-checkout set` to expand the set of directories you want to see,
+or `git sparse-checkout disable` to expand to all files (see
+linkgit:git-sparse-checkout[1] for more details). You can explore the
+subdirectories outside your sparse-checkout by using `git ls-tree
+HEAD[:<directory>]`.
+
+-b <name>::
+--branch <name>::
+	Instead of checking out the branch pointed to by the cloned
+	repository's HEAD, check out the `<name>` branch instead.
+
+--[no-]full-clone::
+	A sparse-checkout is initialized by default. This behavior can be
+	turned off via `--full-clone`.
+
 List
 ~~~~
 

@@ -64,7 +90,7 @@ unregister [<enlistment>]::
 
 SEE ALSO
 --------
-linkgit:git-maintenance[1].
+linkgit:git-clone[1], linkgit:git-maintenance[1].
 
 Scalar
 ---

@@ -10,6 +10,9 @@ PATH=$PWD/..:$PATH
 
 . ../../../t/test-lib.sh
 
+GIT_TEST_MAINT_SCHEDULER="crontab:test-tool crontab ../cron.txt,launchctl:true,schtasks:true"
+export GIT_TEST_MAINT_SCHEDULER
+
 test_expect_success 'scalar shows a usage' '
 	test_expect_code 129 scalar -h
 '

@@ -29,4 +32,33 @@ test_expect_success 'scalar unregister' '
 	! grep -F "$(pwd)/vanish/src" scalar.repos
 '
 
+test_expect_success 'set up repository to clone' '
+	test_commit first &&
+	test_commit second &&
+	test_commit third &&
+	git switch -c parallel first &&
+	mkdir -p 1/2 &&
+	test_commit 1/2/3 &&
+	git config uploadPack.allowFilter true &&
+	git config uploadPack.allowAnySHA1InWant true
+'
+
+test_expect_success 'scalar clone' '
+	second=$(git rev-parse --verify second:second.t) &&
+	scalar clone "file://$(pwd)" cloned &&
+	(
+		cd cloned/src &&
+
+		git config --get --global --fixed-value maintenance.repo \
+			"$(pwd)" &&
+
+		test_path_is_missing 1/2 &&
+		test_must_fail git rev-list --missing=print $second &&
+		git rev-list $second &&
+		git cat-file blob $second >actual &&
+		echo "second" >expect &&
+		test_cmp expect actual
+	)
+'
+
 test_done

@@ -251,6 +251,16 @@ static int unregister_dir(void)
 	return res;
 }
 
+static int cmd_list(int argc, const char **argv)
+{
+	if (argc != 1)
+		die(_("`scalar list` does not take arguments"));
+
+	if (run_git("config", "--global", "--get-all", "scalar.repo", NULL) < 0)
+		return -1;
+	return 0;
+}
+
 static int cmd_register(int argc, const char **argv)
 {
 	struct option options[] = {

@@ -337,6 +347,7 @@ static struct {
 	const char *name;
 	int (*fn)(int, const char **);
 } builtins[] = {
+	{ "list", cmd_list },
 	{ "register", cmd_register },
 	{ "unregister", cmd_unregister },
 	{ NULL, NULL},

@@ -8,6 +8,7 @@ scalar - an opinionated repository management tool
 SYNOPSIS
 --------
 [verse]
+scalar list
 scalar register [<enlistment>]
 scalar unregister [<enlistment>]
 

@@ -28,11 +29,19 @@ an existing Git worktree with Scalar whose name is not `src`, the enlistment
 will be identical to the worktree.
 
 The `scalar` command implements various subcommands, and different options
-depending on the subcommand.
+depending on the subcommand. With the exception of `list`, all subcommands
+expect to be run in an enlistment.
 
 COMMANDS
 --------
 
+List
+~~~~
+
+list::
+	List enlistments that are currently registered by Scalar. This
+	subcommand does not need to be run inside an enlistment.
+
 Register
 ~~~~~~~~
 

@@ -269,6 +269,24 @@ static int cmd_register(int argc, const char **argv)
 	return register_dir();
 }
 
+static int remove_deleted_enlistment(struct strbuf *path)
+{
+	int res = 0;
+	strbuf_realpath_forgiving(path, path->buf, 1);
+
+	if (run_git("config", "--global",
+		    "--unset", "--fixed-value",
+		    "scalar.repo", path->buf, NULL) < 0)
+		res = -1;
+
+	if (run_git("config", "--global",
+		    "--unset", "--fixed-value",
+		    "maintenance.repo", path->buf, NULL) < 0)
+		res = -1;
+
+	return res;
+}
+
 static int cmd_unregister(int argc, const char **argv)
 {
 	struct option options[] = {

@@ -282,6 +300,34 @@ static int cmd_unregister(int argc, const char **argv)
 	argc = parse_options(argc, argv, NULL, options,
 			     usage, 0);
 
+	/*
+	 * Be forgiving when the enlistment or worktree does not even exist any
+	 * longer; This can be the case if a user deleted the worktree by
+	 * mistake and _still_ wants to unregister the thing.
+	 */
+	if (argc == 1) {
+		struct strbuf src_path = STRBUF_INIT, workdir_path = STRBUF_INIT;
+
+		strbuf_addf(&src_path, "%s/src/.git", argv[0]);
+		strbuf_addf(&workdir_path, "%s/.git", argv[0]);
+		if (!is_directory(src_path.buf) && !is_directory(workdir_path.buf)) {
+			/* remove possible matching registrations */
+			int res = -1;
+
+			strbuf_strip_suffix(&src_path, "/.git");
+			res = remove_deleted_enlistment(&src_path) && res;
+
+			strbuf_strip_suffix(&workdir_path, "/.git");
+			res = remove_deleted_enlistment(&workdir_path) && res;
+
+			strbuf_release(&src_path);
+			strbuf_release(&workdir_path);
+			return res;
+		}
+		strbuf_release(&src_path);
+		strbuf_release(&workdir_path);
+	}
+
 	setup_enlistment_directory(argc, argv, usage, options, NULL);
 
 	return unregister_dir();

@@ -14,4 +14,19 @@ test_expect_success 'scalar shows a usage' '
 	test_expect_code 129 scalar -h
 '
 
+test_expect_success 'scalar unregister' '
+	git init vanish/src &&
+	scalar register vanish/src &&
+	git config --get --global --fixed-value \
+		maintenance.repo "$(pwd)/vanish/src" &&
+	scalar list >scalar.repos &&
+	grep -F "$(pwd)/vanish/src" scalar.repos &&
+	rm -rf vanish/src/.git &&
+	scalar unregister vanish &&
+	test_must_fail git config --get --global --fixed-value \
+		maintenance.repo "$(pwd)/vanish/src" &&
+	scalar list >scalar.repos &&
+	! grep -F "$(pwd)/vanish/src" scalar.repos
+'
+
 test_done

@@ -327,12 +327,15 @@ static char *remote_default_branch(const char *url)
 static int cmd_clone(int argc, const char **argv)
 {
 	const char *branch = NULL;
-	int full_clone = 0;
+	int full_clone = 0, single_branch = 0;
 	struct option clone_options[] = {
 		OPT_STRING('b', "branch", &branch, N_("<branch>"),
 			   N_("branch to checkout after clone")),
 		OPT_BOOL(0, "full-clone", &full_clone,
 			 N_("when cloning, create full working directory")),
+		OPT_BOOL(0, "single-branch", &single_branch,
+			 N_("only download metadata for the branch that will "
+			    "be checked out")),
 		OPT_END(),
 	};
 	const char * const clone_usage[] = {

@@ -403,7 +406,9 @@ static int cmd_clone(int argc, const char **argv)
 
 	if (set_config("remote.origin.url=%s", url) ||
 	    set_config("remote.origin.fetch="
-		       "+refs/heads/*:refs/remotes/origin/*") ||
+		       "+refs/heads/%s:refs/remotes/origin/%s",
+		       single_branch ? branch : "*",
+		       single_branch ? branch : "*") ||
 	    set_config("remote.origin.promisor=true") ||
 	    set_config("remote.origin.partialCloneFilter=blob:none")) {
 		res = error(_("could not configure remote in '%s'"), dir);

@@ -8,7 +8,7 @@ scalar - an opinionated repository management tool
 SYNOPSIS
 --------
 [verse]
-scalar clone [--branch <main-branch>] [--full-clone] <url> [<enlistment>]
+scalar clone [--single-branch] [--branch <main-branch>] [--full-clone] <url> [<enlistment>]
 scalar list
 scalar register [<enlistment>]
 scalar unregister [<enlistment>]

@@ -57,6 +57,16 @@ HEAD[:<directory>]`.
 	Instead of checking out the branch pointed to by the cloned
 	repository's HEAD, check out the `<name>` branch instead.
 
+--[no-]single-branch::
+	Clone only the history leading to the tip of a single branch, either
+	specified by the `--branch` option or the primary branch remote's
+	`HEAD` points at.
++
+Further fetches into the resulting repository will only update the
+remote-tracking branch for the branch this option was used for the initial
+cloning. If the HEAD at the remote did not point at any branch when
+`--single-branch` clone was made, no remote-tracking branch is created.
+
 --[no-]full-clone::
 	A sparse-checkout is initialized by default. This behavior can be
 	turned off via `--full-clone`.

@@ -45,13 +45,17 @@ test_expect_success 'set up repository to clone' '
 
 test_expect_success 'scalar clone' '
 	second=$(git rev-parse --verify second:second.t) &&
-	scalar clone "file://$(pwd)" cloned &&
+	scalar clone "file://$(pwd)" cloned --single-branch &&
 	(
 		cd cloned/src &&
 
 		git config --get --global --fixed-value maintenance.repo \
 			"$(pwd)" &&
 
+		git for-each-ref --format="%(refname)" refs/remotes/origin/ >actual &&
+		echo "refs/remotes/origin/parallel" >expect &&
+		test_cmp expect actual &&
+
 		test_path_is_missing 1/2 &&
 		test_must_fail git rev-list --missing=print $second &&
 		git rev-list $second &&

@@ -484,6 +484,69 @@ static int cmd_register(int argc, const char **argv)
 	return register_dir();
 }
 
+static int cmd_run(int argc, const char **argv)
+{
+	struct option options[] = {
+		OPT_END(),
+	};
+	struct {
+		const char *arg, *task;
+	} tasks[] = {
+		{ "config", NULL },
+		{ "commit-graph", "commit-graph" },
+		{ "fetch", "prefetch" },
+		{ "loose-objects", "loose-objects" },
+		{ "pack-files", "incremental-repack" },
+		{ NULL, NULL }
+	};
+	struct strbuf buf = STRBUF_INIT;
+	const char *usagestr[] = { NULL, NULL };
+	int i;
+
+	strbuf_addstr(&buf, N_("scalar run <task> [<enlistment>]\nTasks:\n"));
+	for (i = 0; tasks[i].arg; i++)
+		strbuf_addf(&buf, "\t%s\n", tasks[i].arg);
+	usagestr[0] = buf.buf;
+
+	argc = parse_options(argc, argv, NULL, options,
+			     usagestr, 0);
+
+	if (!argc)
+		usage_with_options(usagestr, options);
+
+	if (!strcmp("all", argv[0])) {
+		i = -1;
+	} else {
+		for (i = 0; tasks[i].arg && strcmp(tasks[i].arg, argv[0]); i++)
+			; /* keep looking for the task */
+
+		if (i > 0 && !tasks[i].arg) {
+			error(_("no such task: '%s'"), argv[0]);
+			usage_with_options(usagestr, options);
+		}
+	}
+
+	argc--;
+	argv++;
+	setup_enlistment_directory(argc, argv, usagestr, options, NULL);
+	strbuf_release(&buf);
+
+	if (i == 0)
+		return register_dir();
+
+	if (i > 0)
+		return run_git("maintenance", "run",
+			       "--task", tasks[i].task, NULL);
+
+	if (register_dir())
+		return -1;
+	for (i = 1; tasks[i].arg; i++)
+		if (run_git("maintenance", "run",
+			    "--task", tasks[i].task, NULL))
+			return -1;
+	return 0;
+}
+
 static int remove_deleted_enlistment(struct strbuf *path)
 {
 	int res = 0;

@@ -556,6 +619,7 @@ static struct {
 	{ "list", cmd_list },
 	{ "register", cmd_register },
 	{ "unregister", cmd_unregister },
+	{ "run", cmd_run },
 	{ NULL, NULL},
 };
 

@@ -12,6 +12,7 @@ scalar clone [--single-branch] [--branch <main-branch>] [--full-clone] <url> [<e
 scalar list
 scalar register [<enlistment>]
 scalar unregister [<enlistment>]
+scalar run ( all | config | commit-graph | fetch | loose-objects | pack-files ) [<enlistment>]
 
 DESCRIPTION
 -----------

@@ -98,6 +99,24 @@ unregister [<enlistment>]::
 	Remove the specified repository from the list of repositories
 	registered with Scalar and stop the scheduled background maintenance.
 
+Run
+~~~
+
+scalar run ( all | config | commit-graph | fetch | loose-objects | pack-files ) [<enlistment>]::
+	Run the given maintenance task (or all tasks, if `all` was specified).
+	Except for `all` and `config`, this subcommand simply hands off to
+	linkgit:git-maintenance[1] (mapping `fetch` to `prefetch` and
+	`pack-files` to `incremental-repack`).
++
+These tasks are run automatically as part of the scheduled maintenance,
+as soon as the repository is registered with Scalar. It should therefore
+not be necessary to run this subcommand manually.
++
+The `config` task is specific to Scalar and configures all those
+opinionated default settings that make Git work more efficiently with
+large repositories. As this task is run as part of `scalar clone`
+automatically, explicit invocations of this task are rarely needed.
+
 SEE ALSO
 --------
 linkgit:git-clone[1], linkgit:git-maintenance[1].

@@ -108,18 +108,20 @@ static int run_git(const char *arg, ...)
 	return res;
 }
 
-static int set_recommended_config(void)
+static int set_recommended_config(int reconfigure)
 {
 	struct {
 		const char *key;
 		const char *value;
+		int overwrite_on_reconfigure;
 	} config[] = {
-		{ "am.keepCR", "true" },
-		{ "core.FSCache", "true" },
-		{ "core.multiPackIndex", "true" },
-		{ "core.preloadIndex", "true" },
+		/* Required */
+		{ "am.keepCR", "true", 1 },
+		{ "core.FSCache", "true", 1 },
+		{ "core.multiPackIndex", "true", 1 },
+		{ "core.preloadIndex", "true", 1 },
 #ifndef WIN32
-		{ "core.untrackedCache", "true" },
+		{ "core.untrackedCache", "true", 1 },
 #else
 		/*
 		 * Unfortunately, Scalar's Functional Tests demonstrated

@@ -133,28 +135,29 @@ static int set_recommended_config(void)
 		 * Therefore, with a sad heart, we disable this very useful
 		 * feature on Windows.
 		 */
-		{ "core.untrackedCache", "false" },
+		{ "core.untrackedCache", "false", 1 },
 #endif
-		{ "core.logAllRefUpdates", "true" },
-		{ "credential.https://dev.azure.com.useHttpPath", "true" },
-		{ "credential.validate", "false" }, /* GCM4W-only */
-		{ "gc.auto", "0" },
-		{ "gui.GCWarning", "false" },
-		{ "index.threads", "true" },
-		{ "index.version", "4" },
-		{ "merge.stat", "false" },
-		{ "merge.renames", "true" },
-		{ "pack.useBitmaps", "false" },
-		{ "pack.useSparse", "true" },
-		{ "receive.autoGC", "false" },
-		{ "reset.quiet", "true" },
-		{ "feature.manyFiles", "false" },
-		{ "feature.experimental", "false" },
-		{ "fetch.unpackLimit", "1" },
-		{ "fetch.writeCommitGraph", "false" },
+		{ "core.logAllRefUpdates", "true", 1 },
+		{ "credential.https://dev.azure.com.useHttpPath", "true", 1 },
+		{ "credential.validate", "false", 1 }, /* GCM4W-only */
+		{ "gc.auto", "0", 1 },
+		{ "gui.GCWarning", "false", 1 },
+		{ "index.threads", "true", 1 },
+		{ "index.version", "4", 1 },
+		{ "merge.stat", "false", 1 },
+		{ "merge.renames", "true", 1 },
+		{ "pack.useBitmaps", "false", 1 },
+		{ "pack.useSparse", "true", 1 },
+		{ "receive.autoGC", "false", 1 },
+		{ "reset.quiet", "true", 1 },
+		{ "feature.manyFiles", "false", 1 },
+		{ "feature.experimental", "false", 1 },
+		{ "fetch.unpackLimit", "1", 1 },
+		{ "fetch.writeCommitGraph", "false", 1 },
 #ifdef WIN32
-		{ "http.sslBackend", "schannel" },
+		{ "http.sslBackend", "schannel", 1 },
 #endif
+		/* Optional */
 		{ "status.aheadBehind", "false" },
 		{ "commitGraph.generationVersion", "1" },
 		{ "core.autoCRLF", "false" },

@@ -166,7 +169,8 @@ static int set_recommended_config(void)
 	char *value;
 
 	for (i = 0; config[i].key; i++) {
-		if (git_config_get_string(config[i].key, &value)) {
+		if ((reconfigure && config[i].overwrite_on_reconfigure) ||
+		    git_config_get_string(config[i].key, &value)) {
 			trace2_data_string("scalar", the_repository, config[i].key, "created");
 			if (git_config_set_gently(config[i].key,
 						  config[i].value) < 0)

@@ -231,7 +235,7 @@ static int register_dir(void)
 	int res = add_or_remove_enlistment(1);
 
 	if (!res)
-		res = set_recommended_config();
+		res = set_recommended_config(0);
 
 	if (!res)
 		res = toggle_maintenance(1);

@@ -419,7 +423,7 @@ static int cmd_clone(int argc, const char **argv)
 	    (res = run_git("sparse-checkout", "init", "--cone", NULL)))
 		goto cleanup;
 
-	if (set_recommended_config())
+	if (set_recommended_config(0))
 		return error(_("could not configure '%s'"), dir);
 
 	if ((res = run_git("fetch", "--quiet", "origin", NULL))) {

@@ -484,6 +488,24 @@ static int cmd_register(int argc, const char **argv)
 	return register_dir();
 }
 
+static int cmd_reconfigure(int argc, const char **argv)
+{
+	struct option options[] = {
+		OPT_END(),
+	};
+	const char * const usage[] = {
+		N_("scalar reconfigure [<enlistment>]"),
+		NULL
+	};
+
+	argc = parse_options(argc, argv, NULL, options,
+			     usage, 0);
+
+	setup_enlistment_directory(argc, argv, usage, options, NULL);
+
+	return set_recommended_config(1);
+}
+
 static int cmd_run(int argc, const char **argv)
 {
 	struct option options[] = {

@@ -620,6 +642,7 @@ static struct {
 	{ "register", cmd_register },
 	{ "unregister", cmd_unregister },
 	{ "run", cmd_run },
+	{ "reconfigure", cmd_reconfigure },
 	{ NULL, NULL},
 };
 

@@ -13,6 +13,7 @@ scalar list
 scalar register [<enlistment>]
 scalar unregister [<enlistment>]
 scalar run ( all | config | commit-graph | fetch | loose-objects | pack-files ) [<enlistment>]
+scalar reconfigure <enlistment>
 
 DESCRIPTION
 -----------

@@ -117,6 +118,13 @@ opinionated default settings that make Git work more efficiently with
 large repositories. As this task is run as part of `scalar clone`
 automatically, explicit invocations of this task are rarely needed.
 
+Reconfigure
+~~~~~~~~~~~
+
+After a Scalar upgrade, or when the configuration of a Scalar enlistment
+was somehow corrupted or changed by mistake, this subcommand allows to
+reconfigure the enlistment.
+
 SEE ALSO
 --------
 linkgit:git-clone[1], linkgit:git-maintenance[1].

@@ -65,4 +65,12 @@ test_expect_success 'scalar clone' '
 	)
 '
 
+test_expect_success 'scalar reconfigure' '
+	git init one/src &&
+	scalar register one &&
+	git -C one/src config core.preloadIndex false &&
+	scalar reconfigure one &&
+	test true = "$(git -C one/src config core.preloadIndex)"
+'
+
 test_done

@@ -488,22 +488,77 @@ static int cmd_register(int argc, const char **argv)
 	return register_dir();
 }
 
+static int get_scalar_repos(const char *key, const char *value, void *data)
+{
+	struct string_list *list = data;
+
+	if (!strcmp(key, "scalar.repo"))
+		string_list_append(list, value);
+
+	return 0;
+}
+
 static int cmd_reconfigure(int argc, const char **argv)
 {
+	int all = 0;
 	struct option options[] = {
+		OPT_BOOL('a', "all", &all,
+			 N_("reconfigure all registered enlistments")),
 		OPT_END(),
 	};
 	const char * const usage[] = {
-		N_("scalar reconfigure [<enlistment>]"),
+		N_("scalar reconfigure [--all | <enlistment>]"),
 		NULL
 	};
+	struct string_list scalar_repos = STRING_LIST_INIT_DUP;
+	int i, res = 0;
+	struct repository r = { NULL };
+	struct strbuf commondir = STRBUF_INIT, gitdir = STRBUF_INIT;
 
 	argc = parse_options(argc, argv, NULL, options,
 			     usage, 0);
 
-	setup_enlistment_directory(argc, argv, usage, options, NULL);
+	if (!all) {
+		setup_enlistment_directory(argc, argv, usage, options, NULL);
+
+		return set_recommended_config(1);
+	}
+
+	if (argc > 0)
+		usage_msg_opt(_("--all or <enlistment>, but not both"),
+			      usage, options);
+
+	git_config(get_scalar_repos, &scalar_repos);
 
-	return set_recommended_config(1);
+	for (i = 0; i < scalar_repos.nr; i++) {
+		const char *dir = scalar_repos.items[i].string;
+
+		strbuf_reset(&commondir);
+		strbuf_reset(&gitdir);
+
+		if (chdir(dir) < 0) {
+			warning_errno(_("could not switch to '%s'"), dir);
+			res = -1;
+		} else if (discover_git_directory(&commondir, &gitdir) < 0) {
+			warning_errno(_("git repository gone in '%s'"), dir);
+			res = -1;
+		} else {
+			git_config_clear();
+
+			the_repository = &r;
+			r.commondir = commondir.buf;
+			r.gitdir = gitdir.buf;
+
+			if (set_recommended_config(1) < 0)
+				res = -1;
+		}
+	}
+
+	string_list_clear(&scalar_repos, 1);
+	strbuf_release(&commondir);
+	strbuf_release(&gitdir);
+
+	return res;
 }
 
 static int cmd_run(int argc, const char **argv)

@@ -13,7 +13,7 @@ scalar list
 scalar register [<enlistment>]
 scalar unregister [<enlistment>]
 scalar run ( all | config | commit-graph | fetch | loose-objects | pack-files ) [<enlistment>]
-scalar reconfigure <enlistment>
+scalar reconfigure [ --all | <enlistment> ]
 
 DESCRIPTION
 -----------

@@ -32,8 +32,8 @@ an existing Git worktree with Scalar whose name is not `src`, the enlistment
 will be identical to the worktree.
 
 The `scalar` command implements various subcommands, and different options
-depending on the subcommand. With the exception of `clone` and `list`, all
-subcommands expect to be run in an enlistment.
+depending on the subcommand. With the exception of `clone`, `list` and
+`reconfigure --all`, all subcommands expect to be run in an enlistment.
 
 COMMANDS
 --------

@@ -125,6 +125,9 @@ After a Scalar upgrade, or when the configuration of a Scalar enlistment
 was somehow corrupted or changed by mistake, this subcommand allows to
 reconfigure the enlistment.
 
+With the `--all` option, all enlistments currently registered with Scalar
+will be reconfigured. Use this option after each Scalar upgrade.
+
 SEE ALSO
 --------
 linkgit:git-clone[1], linkgit:git-maintenance[1].

@@ -70,6 +70,9 @@ test_expect_success 'scalar reconfigure' '
 	scalar register one &&
 	git -C one/src config core.preloadIndex false &&
 	scalar reconfigure one &&
+	test true = "$(git -C one/src config core.preloadIndex)" &&
+	git -C one/src config core.preloadIndex false &&
+	scalar reconfigure -a &&
 	test true = "$(git -C one/src config core.preloadIndex)"
 '
 

@@ -8,6 +8,8 @@
 #include "config.h"
 #include "run-command.h"
 #include "refs.h"
+#include "dir.h"
+#include "packfile.h"
 
 /*
  * Remove the deepest subdirectory in the provided path string. Path must not

@@ -328,6 +330,33 @@ static char *remote_default_branch(const char *url)
 	return NULL;
 }
 
+static int delete_enlistment(struct strbuf *enlistment)
+{
+#ifdef WIN32
+	struct strbuf parent = STRBUF_INIT;
+#endif
+
+	if (unregister_dir())
+		die(_("failed to unregister repository"));
+
+#ifdef WIN32
+	/*
+	 * Change the current directory to one outside of the enlistment so
+	 * that we may delete everything underneath it.
+	 */
+	strbuf_addbuf(&parent, enlistment);
+	strbuf_parent_directory(&parent);
+	if (chdir(parent.buf) < 0)
+		die_errno(_("could not switch to '%s'"), parent.buf);
+	strbuf_release(&parent);
+#endif
+
+	if (remove_dir_recursively(enlistment, 0))
+		die(_("failed to delete enlistment directory"));
+
+	return 0;
+}
+
 static int cmd_clone(int argc, const char **argv)
 {
 	const char *branch = NULL;