Revision 7b70e9efb18c2cc3f219af399bd384c5801ba1d7 authored by Jeff King on 16 April 2024, 08:35:33 UTC, committed by Johannes Schindelin on 17 April 2024, 20:29:56 UTC
The upload-pack command tries to avoid trusting the repository in which
it's run (e.g., by not running any hooks and not using any config that
contains arbitrary commands). But if the server side of a fetch or a
clone is a partial clone, then either upload-pack or its child
pack-objects may run a lazy "git fetch" under the hood. And it is very
easy to convince fetch to run arbitrary commands.

The "server" side can be a local repository owned by someone else, who
would be able to configure commands that are run during a clone with the
current user's permissions. This issue has been designated
CVE-2024-32004.

The fix in this commit's parent helps in this scenario, as well as in
related scenarios using SSH to clone, where the untrusted .git directory
is owned by a different user id. But if you received one as a zip file,
on a USB stick, etc, it may be owned by your user but still untrusted.

This has been designated CVE-2024-32465.

To mitigate the issue more completely, let's disable lazy fetching
entirely during `upload-pack`. While fetching from a partial repository
should be relatively rare, it is certainly not an unreasonable workflow.
And thus we need to provide an escape hatch.

This commit works by respecting a GIT_NO_LAZY_FETCH environment variable
(to skip the lazy-fetch), and setting it in upload-pack, but only when
the user has not already done so (which gives us the escape hatch).

The name of the variable is specifically chosen to match what has
already been added in 'master' via e6d5479e7a (git: extend
--no-lazy-fetch to work across subprocesses, 2024-02-27). Since we're
building this fix as a backport for older versions, we could cherry-pick
that patch and its earlier steps. However, we don't really need the
niceties (like a "--no-lazy-fetch" option) that it offers. By using the
same name, everything should just work when the two are eventually
merged, but here are a few notes:

  - the blocking of the fetch in e6d5479e7a is incomplete! It sets
    fetch_if_missing to 0 when we setup the repository variable, but
    that isn't enough. pack-objects in particular will call
    prefetch_to_pack() even if that variable is 0. This patch by
    contrast checks the environment variable at the lowest level before
    we call the lazy fetch, where we can be sure to catch all code
    paths.

    Possibly the setting of fetch_if_missing from e6d5479e7a can be
    reverted, but it may be useful to have. For example, some code may
    want to use that flag to change behavior before it gets to the point
    of trying to start the fetch. At any rate, that's all outside the
    scope of this patch.

  - there's documentation for GIT_NO_LAZY_FETCH in e6d5479e7a. We can
    live without that here, because for the most part the user shouldn't
    need to set it themselves. The exception is if they do want to
    override upload-pack's default, and that requires a separate
    documentation section (which is added here)

  - it would be nice to use the NO_LAZY_FETCH_ENVIRONMENT macro added by
    e6d5479e7a, but those definitions have moved from cache.h to
    environment.h between 2.39.3 and master. I just used the raw string
    literals, and we can replace them with the macro once this topic is
    merged to master.

At least with respect to CVE-2024-32004, this does render this commit's
parent commit somewhat redundant. However, it is worth retaining that
commit as defense in depth, and because it may help other issues (e.g.,
symlink/hardlink TOCTOU races, where zip files are not really an
interesting attack vector).

The tests in t0411 still pass, but now we have _two_ mechanisms ensuring
that the evil command is not run. Let's beef up the existing ones to
check that they failed for the expected reason, that we refused to run
upload-pack at all with an alternate user id. And add two new ones for
the same-user case that both the restriction and its escape hatch.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
1 parent f4aa8c8
Raw File
git.c
#include "builtin.h"
#include "config.h"
#include "exec-cmd.h"
#include "help.h"
#include "run-command.h"
#include "alias.h"
#include "shallow.h"

#define RUN_SETUP		(1<<0)
#define RUN_SETUP_GENTLY	(1<<1)
#define USE_PAGER		(1<<2)
/*
 * require working tree to be present -- anything uses this needs
 * RUN_SETUP for reading from the configuration file.
 */
#define NEED_WORK_TREE		(1<<3)
#define SUPPORT_SUPER_PREFIX	(1<<4)
#define DELAY_PAGER_CONFIG	(1<<5)
#define NO_PARSEOPT		(1<<6) /* parse-options is not used */

struct cmd_struct {
	const char *cmd;
	int (*fn)(int, const char **, const char *);
	unsigned int option;
};

const char git_usage_string[] =
	N_("git [-v | --version] [-h | --help] [-C <path>] [-c <name>=<value>]\n"
	   "           [--exec-path[=<path>]] [--html-path] [--man-path] [--info-path]\n"
	   "           [-p | --paginate | -P | --no-pager] [--no-replace-objects] [--bare]\n"
	   "           [--git-dir=<path>] [--work-tree=<path>] [--namespace=<name>]\n"
	   "           [--super-prefix=<path>] [--config-env=<name>=<envvar>]\n"
	   "           <command> [<args>]");

const char git_more_info_string[] =
	N_("'git help -a' and 'git help -g' list available subcommands and some\n"
	   "concept guides. See 'git help <command>' or 'git help <concept>'\n"
	   "to read about a specific subcommand or concept.\n"
	   "See 'git help git' for an overview of the system.");

static int use_pager = -1;

static void list_builtins(struct string_list *list, unsigned int exclude_option);

static void exclude_helpers_from_list(struct string_list *list)
{
	int i = 0;

	while (i < list->nr) {
		if (strstr(list->items[i].string, "--"))
			unsorted_string_list_delete_item(list, i, 0);
		else
			i++;
	}
}

static int match_token(const char *spec, int len, const char *token)
{
	int token_len = strlen(token);

	return len == token_len && !strncmp(spec, token, token_len);
}

static int list_cmds(const char *spec)
{
	struct string_list list = STRING_LIST_INIT_DUP;
	int i;
	int nongit;

	/*
	* Set up the repository so we can pick up any repo-level config (like
	* completion.commands).
	*/
	setup_git_directory_gently(&nongit);

	while (*spec) {
		const char *sep = strchrnul(spec, ',');
		int len = sep - spec;

		if (match_token(spec, len, "builtins"))
			list_builtins(&list, 0);
		else if (match_token(spec, len, "main"))
			list_all_main_cmds(&list);
		else if (match_token(spec, len, "others"))
			list_all_other_cmds(&list);
		else if (match_token(spec, len, "nohelpers"))
			exclude_helpers_from_list(&list);
		else if (match_token(spec, len, "alias"))
			list_aliases(&list);
		else if (match_token(spec, len, "config"))
			list_cmds_by_config(&list);
		else if (len > 5 && !strncmp(spec, "list-", 5)) {
			struct strbuf sb = STRBUF_INIT;

			strbuf_add(&sb, spec + 5, len - 5);
			list_cmds_by_category(&list, sb.buf);
			strbuf_release(&sb);
		}
		else
			die(_("unsupported command listing type '%s'"), spec);
		spec += len;
		if (*spec == ',')
			spec++;
	}
	for (i = 0; i < list.nr; i++)
		puts(list.items[i].string);
	string_list_clear(&list, 0);
	return 0;
}

static void commit_pager_choice(void)
{
	switch (use_pager) {
	case 0:
		setenv("GIT_PAGER", "cat", 1);
		break;
	case 1:
		setup_pager();
		break;
	default:
		break;
	}
}

void setup_auto_pager(const char *cmd, int def)
{
	if (use_pager != -1 || pager_in_use())
		return;
	use_pager = check_pager_config(cmd);
	if (use_pager == -1)
		use_pager = def;
	commit_pager_choice();
}

static int handle_options(const char ***argv, int *argc, int *envchanged)
{
	const char **orig_argv = *argv;

	while (*argc > 0) {
		const char *cmd = (*argv)[0];
		if (cmd[0] != '-')
			break;

		/*
		 * For legacy reasons, the "version" and "help"
		 * commands can be written with "--" prepended
		 * to make them look like flags.
		 */
		if (!strcmp(cmd, "--help") || !strcmp(cmd, "-h") ||
		    !strcmp(cmd, "--version") || !strcmp(cmd, "-v"))
			break;

		/*
		 * Check remaining flags.
		 */
		if (skip_prefix(cmd, "--exec-path", &cmd)) {
			if (*cmd == '=')
				git_set_exec_path(cmd + 1);
			else {
				puts(git_exec_path());
				trace2_cmd_name("_query_");
				exit(0);
			}
		} else if (!strcmp(cmd, "--html-path")) {
			puts(system_path(GIT_HTML_PATH));
			trace2_cmd_name("_query_");
			exit(0);
		} else if (!strcmp(cmd, "--man-path")) {
			puts(system_path(GIT_MAN_PATH));
			trace2_cmd_name("_query_");
			exit(0);
		} else if (!strcmp(cmd, "--info-path")) {
			puts(system_path(GIT_INFO_PATH));
			trace2_cmd_name("_query_");
			exit(0);
		} else if (!strcmp(cmd, "-p") || !strcmp(cmd, "--paginate")) {
			use_pager = 1;
		} else if (!strcmp(cmd, "-P") || !strcmp(cmd, "--no-pager")) {
			use_pager = 0;
			if (envchanged)
				*envchanged = 1;
		} else if (!strcmp(cmd, "--no-replace-objects")) {
			read_replace_refs = 0;
			setenv(NO_REPLACE_OBJECTS_ENVIRONMENT, "1", 1);
			if (envchanged)
				*envchanged = 1;
		} else if (!strcmp(cmd, "--git-dir")) {
			if (*argc < 2) {
				fprintf(stderr, _("no directory given for '%s' option\n" ), "--git-dir");
				usage(git_usage_string);
			}
			setenv(GIT_DIR_ENVIRONMENT, (*argv)[1], 1);
			if (envchanged)
				*envchanged = 1;
			(*argv)++;
			(*argc)--;
		} else if (skip_prefix(cmd, "--git-dir=", &cmd)) {
			setenv(GIT_DIR_ENVIRONMENT, cmd, 1);
			if (envchanged)
				*envchanged = 1;
		} else if (!strcmp(cmd, "--namespace")) {
			if (*argc < 2) {
				fprintf(stderr, _("no namespace given for --namespace\n" ));
				usage(git_usage_string);
			}
			setenv(GIT_NAMESPACE_ENVIRONMENT, (*argv)[1], 1);
			if (envchanged)
				*envchanged = 1;
			(*argv)++;
			(*argc)--;
		} else if (skip_prefix(cmd, "--namespace=", &cmd)) {
			setenv(GIT_NAMESPACE_ENVIRONMENT, cmd, 1);
			if (envchanged)
				*envchanged = 1;
		} else if (!strcmp(cmd, "--work-tree")) {
			if (*argc < 2) {
				fprintf(stderr, _("no directory given for '%s' option\n" ), "--work-tree");
				usage(git_usage_string);
			}
			setenv(GIT_WORK_TREE_ENVIRONMENT, (*argv)[1], 1);
			if (envchanged)
				*envchanged = 1;
			(*argv)++;
			(*argc)--;
		} else if (skip_prefix(cmd, "--work-tree=", &cmd)) {
			setenv(GIT_WORK_TREE_ENVIRONMENT, cmd, 1);
			if (envchanged)
				*envchanged = 1;
		} else if (!strcmp(cmd, "--super-prefix")) {
			if (*argc < 2) {
				fprintf(stderr, _("no prefix given for --super-prefix\n" ));
				usage(git_usage_string);
			}
			setenv(GIT_SUPER_PREFIX_ENVIRONMENT, (*argv)[1], 1);
			if (envchanged)
				*envchanged = 1;
			(*argv)++;
			(*argc)--;
		} else if (skip_prefix(cmd, "--super-prefix=", &cmd)) {
			setenv(GIT_SUPER_PREFIX_ENVIRONMENT, cmd, 1);
			if (envchanged)
				*envchanged = 1;
		} else if (!strcmp(cmd, "--bare")) {
			char *cwd = xgetcwd();
			is_bare_repository_cfg = 1;
			setenv(GIT_DIR_ENVIRONMENT, cwd, 0);
			free(cwd);
			setenv(GIT_IMPLICIT_WORK_TREE_ENVIRONMENT, "0", 1);
			if (envchanged)
				*envchanged = 1;
		} else if (!strcmp(cmd, "-c")) {
			if (*argc < 2) {
				fprintf(stderr, _("-c expects a configuration string\n" ));
				usage(git_usage_string);
			}
			git_config_push_parameter((*argv)[1]);
			(*argv)++;
			(*argc)--;
		} else if (!strcmp(cmd, "--config-env")) {
			if (*argc < 2) {
				fprintf(stderr, _("no config key given for --config-env\n" ));
				usage(git_usage_string);
			}
			git_config_push_env((*argv)[1]);
			(*argv)++;
			(*argc)--;
		} else if (skip_prefix(cmd, "--config-env=", &cmd)) {
			git_config_push_env(cmd);
		} else if (!strcmp(cmd, "--literal-pathspecs")) {
			setenv(GIT_LITERAL_PATHSPECS_ENVIRONMENT, "1", 1);
			if (envchanged)
				*envchanged = 1;
		} else if (!strcmp(cmd, "--no-literal-pathspecs")) {
			setenv(GIT_LITERAL_PATHSPECS_ENVIRONMENT, "0", 1);
			if (envchanged)
				*envchanged = 1;
		} else if (!strcmp(cmd, "--glob-pathspecs")) {
			setenv(GIT_GLOB_PATHSPECS_ENVIRONMENT, "1", 1);
			if (envchanged)
				*envchanged = 1;
		} else if (!strcmp(cmd, "--noglob-pathspecs")) {
			setenv(GIT_NOGLOB_PATHSPECS_ENVIRONMENT, "1", 1);
			if (envchanged)
				*envchanged = 1;
		} else if (!strcmp(cmd, "--icase-pathspecs")) {
			setenv(GIT_ICASE_PATHSPECS_ENVIRONMENT, "1", 1);
			if (envchanged)
				*envchanged = 1;
		} else if (!strcmp(cmd, "--no-optional-locks")) {
			setenv(GIT_OPTIONAL_LOCKS_ENVIRONMENT, "0", 1);
			if (envchanged)
				*envchanged = 1;
		} else if (!strcmp(cmd, "--shallow-file")) {
			(*argv)++;
			(*argc)--;
			set_alternate_shallow_file(the_repository, (*argv)[0], 1);
			if (envchanged)
				*envchanged = 1;
		} else if (!strcmp(cmd, "-C")) {
			if (*argc < 2) {
				fprintf(stderr, _("no directory given for '%s' option\n" ), "-C");
				usage(git_usage_string);
			}
			if ((*argv)[1][0]) {
				if (chdir((*argv)[1]))
					die_errno("cannot change to '%s'", (*argv)[1]);
				if (envchanged)
					*envchanged = 1;
			}
			(*argv)++;
			(*argc)--;
		} else if (skip_prefix(cmd, "--list-cmds=", &cmd)) {
			trace2_cmd_name("_query_");
			if (!strcmp(cmd, "parseopt")) {
				struct string_list list = STRING_LIST_INIT_DUP;
				int i;

				list_builtins(&list, NO_PARSEOPT);
				for (i = 0; i < list.nr; i++)
					printf("%s ", list.items[i].string);
				string_list_clear(&list, 0);
				exit(0);
			} else {
				exit(list_cmds(cmd));
			}
		} else {
			fprintf(stderr, _("unknown option: %s\n"), cmd);
			usage(git_usage_string);
		}

		(*argv)++;
		(*argc)--;
	}
	return (*argv) - orig_argv;
}

static int handle_alias(int *argcp, const char ***argv)
{
	int envchanged = 0, ret = 0, saved_errno = errno;
	int count, option_count;
	const char **new_argv;
	const char *alias_command;
	char *alias_string;

	alias_command = (*argv)[0];
	alias_string = alias_lookup(alias_command);
	if (alias_string) {
		if (*argcp > 1 && !strcmp((*argv)[1], "-h"))
			fprintf_ln(stderr, _("'%s' is aliased to '%s'"),
				   alias_command, alias_string);
		if (alias_string[0] == '!') {
			struct child_process child = CHILD_PROCESS_INIT;
			int nongit_ok;

			/* Aliases expect GIT_PREFIX, GIT_DIR etc to be set */
			setup_git_directory_gently(&nongit_ok);

			commit_pager_choice();

			child.use_shell = 1;
			child.clean_on_exit = 1;
			child.wait_after_clean = 1;
			child.trace2_child_class = "shell_alias";
			strvec_push(&child.args, alias_string + 1);
			strvec_pushv(&child.args, (*argv) + 1);

			trace2_cmd_alias(alias_command, child.args.v);
			trace2_cmd_list_config();
			trace2_cmd_list_env_vars();
			trace2_cmd_name("_run_shell_alias_");

			ret = run_command(&child);
			if (ret >= 0)   /* normal exit */
				exit(ret);

			die_errno(_("while expanding alias '%s': '%s'"),
				  alias_command, alias_string + 1);
		}
		count = split_cmdline(alias_string, &new_argv);
		if (count < 0)
			die(_("bad alias.%s string: %s"), alias_command,
			    _(split_cmdline_strerror(count)));
		option_count = handle_options(&new_argv, &count, &envchanged);
		if (envchanged)
			die(_("alias '%s' changes environment variables.\n"
			      "You can use '!git' in the alias to do this"),
			    alias_command);
		MOVE_ARRAY(new_argv - option_count, new_argv, count);
		new_argv -= option_count;

		if (count < 1)
			die(_("empty alias for %s"), alias_command);

		if (!strcmp(alias_command, new_argv[0]))
			die(_("recursive alias: %s"), alias_command);

		trace_argv_printf(new_argv,
				  "trace: alias expansion: %s =>",
				  alias_command);

		REALLOC_ARRAY(new_argv, count + *argcp);
		/* insert after command name */
		COPY_ARRAY(new_argv + count, *argv + 1, *argcp);

		trace2_cmd_alias(alias_command, new_argv);
		trace2_cmd_list_config();
		trace2_cmd_list_env_vars();

		*argv = new_argv;
		*argcp += count - 1;

		ret = 1;
	}

	errno = saved_errno;

	return ret;
}

static int run_builtin(struct cmd_struct *p, int argc, const char **argv)
{
	int status, help;
	struct stat st;
	const char *prefix;
	int run_setup = (p->option & (RUN_SETUP | RUN_SETUP_GENTLY));

	help = argc == 2 && !strcmp(argv[1], "-h");
	if (help && (run_setup & RUN_SETUP))
		/* demote to GENTLY to allow 'git cmd -h' outside repo */
		run_setup = RUN_SETUP_GENTLY;

	if (run_setup & RUN_SETUP) {
		prefix = setup_git_directory();
	} else if (run_setup & RUN_SETUP_GENTLY) {
		int nongit_ok;
		prefix = setup_git_directory_gently(&nongit_ok);
	} else {
		prefix = NULL;
	}
	assert(!prefix || *prefix);
	precompose_argv_prefix(argc, argv, NULL);
	if (use_pager == -1 && run_setup &&
		!(p->option & DELAY_PAGER_CONFIG))
		use_pager = check_pager_config(p->cmd);
	if (use_pager == -1 && p->option & USE_PAGER)
		use_pager = 1;
	if (run_setup && startup_info->have_repository)
		/* get_git_dir() may set up repo, avoid that */
		trace_repo_setup(prefix);
	commit_pager_choice();

	if (!help && get_super_prefix()) {
		if (!(p->option & SUPPORT_SUPER_PREFIX))
			die(_("%s doesn't support --super-prefix"), p->cmd);
	}

	if (!help && p->option & NEED_WORK_TREE)
		setup_work_tree();

	trace_argv_printf(argv, "trace: built-in: git");
	trace2_cmd_name(p->cmd);
	trace2_cmd_list_config();
	trace2_cmd_list_env_vars();

	validate_cache_entries(the_repository->index);
	status = p->fn(argc, argv, prefix);
	validate_cache_entries(the_repository->index);

	if (status)
		return status;

	/* Somebody closed stdout? */
	if (fstat(fileno(stdout), &st))
		return 0;
	/* Ignore write errors for pipes and sockets.. */
	if (S_ISFIFO(st.st_mode) || S_ISSOCK(st.st_mode))
		return 0;

	/* Check for ENOSPC and EIO errors.. */
	if (fflush(stdout))
		die_errno(_("write failure on standard output"));
	if (ferror(stdout))
		die(_("unknown write failure on standard output"));
	if (fclose(stdout))
		die_errno(_("close failed on standard output"));
	return 0;
}

static struct cmd_struct commands[] = {
	{ "add", cmd_add, RUN_SETUP | NEED_WORK_TREE },
	{ "am", cmd_am, RUN_SETUP | NEED_WORK_TREE },
	{ "annotate", cmd_annotate, RUN_SETUP },
	{ "apply", cmd_apply, RUN_SETUP_GENTLY },
	{ "archive", cmd_archive, RUN_SETUP_GENTLY },
	{ "bisect--helper", cmd_bisect__helper, RUN_SETUP },
	{ "blame", cmd_blame, RUN_SETUP },
	{ "branch", cmd_branch, RUN_SETUP | DELAY_PAGER_CONFIG },
	{ "bugreport", cmd_bugreport, RUN_SETUP_GENTLY },
	{ "bundle", cmd_bundle, RUN_SETUP_GENTLY },
	{ "cat-file", cmd_cat_file, RUN_SETUP },
	{ "check-attr", cmd_check_attr, RUN_SETUP },
	{ "check-ignore", cmd_check_ignore, RUN_SETUP | NEED_WORK_TREE },
	{ "check-mailmap", cmd_check_mailmap, RUN_SETUP },
	{ "check-ref-format", cmd_check_ref_format, NO_PARSEOPT  },
	{ "checkout", cmd_checkout, RUN_SETUP | NEED_WORK_TREE },
	{ "checkout--worker", cmd_checkout__worker,
		RUN_SETUP | NEED_WORK_TREE | SUPPORT_SUPER_PREFIX },
	{ "checkout-index", cmd_checkout_index,
		RUN_SETUP | NEED_WORK_TREE},
	{ "cherry", cmd_cherry, RUN_SETUP },
	{ "cherry-pick", cmd_cherry_pick, RUN_SETUP | NEED_WORK_TREE },
	{ "clean", cmd_clean, RUN_SETUP | NEED_WORK_TREE },
	{ "clone", cmd_clone },
	{ "column", cmd_column, RUN_SETUP_GENTLY },
	{ "commit", cmd_commit, RUN_SETUP | NEED_WORK_TREE },
	{ "commit-graph", cmd_commit_graph, RUN_SETUP },
	{ "commit-tree", cmd_commit_tree, RUN_SETUP },
	{ "config", cmd_config, RUN_SETUP_GENTLY | DELAY_PAGER_CONFIG },
	{ "count-objects", cmd_count_objects, RUN_SETUP },
	{ "credential", cmd_credential, RUN_SETUP_GENTLY | NO_PARSEOPT },
	{ "credential-cache", cmd_credential_cache },
	{ "credential-cache--daemon", cmd_credential_cache_daemon },
	{ "credential-store", cmd_credential_store },
	{ "describe", cmd_describe, RUN_SETUP },
	{ "diagnose", cmd_diagnose, RUN_SETUP_GENTLY },
	{ "diff", cmd_diff, NO_PARSEOPT },
	{ "diff-files", cmd_diff_files, RUN_SETUP | NEED_WORK_TREE | NO_PARSEOPT },
	{ "diff-index", cmd_diff_index, RUN_SETUP | NO_PARSEOPT },
	{ "diff-tree", cmd_diff_tree, RUN_SETUP | NO_PARSEOPT },
	{ "difftool", cmd_difftool, RUN_SETUP_GENTLY },
	{ "env--helper", cmd_env__helper },
	{ "fast-export", cmd_fast_export, RUN_SETUP },
	{ "fast-import", cmd_fast_import, RUN_SETUP | NO_PARSEOPT },
	{ "fetch", cmd_fetch, RUN_SETUP },
	{ "fetch-pack", cmd_fetch_pack, RUN_SETUP | NO_PARSEOPT },
	{ "fmt-merge-msg", cmd_fmt_merge_msg, RUN_SETUP },
	{ "for-each-ref", cmd_for_each_ref, RUN_SETUP },
	{ "for-each-repo", cmd_for_each_repo, RUN_SETUP_GENTLY },
	{ "format-patch", cmd_format_patch, RUN_SETUP },
	{ "fsck", cmd_fsck, RUN_SETUP },
	{ "fsck-objects", cmd_fsck, RUN_SETUP },
	{ "fsmonitor--daemon", cmd_fsmonitor__daemon, SUPPORT_SUPER_PREFIX | RUN_SETUP },
	{ "gc", cmd_gc, RUN_SETUP },
	{ "get-tar-commit-id", cmd_get_tar_commit_id, NO_PARSEOPT },
	{ "grep", cmd_grep, RUN_SETUP_GENTLY },
	{ "hash-object", cmd_hash_object },
	{ "help", cmd_help },
	{ "hook", cmd_hook, RUN_SETUP },
	{ "index-pack", cmd_index_pack, RUN_SETUP_GENTLY | NO_PARSEOPT },
	{ "init", cmd_init_db },
	{ "init-db", cmd_init_db },
	{ "interpret-trailers", cmd_interpret_trailers, RUN_SETUP_GENTLY },
	{ "log", cmd_log, RUN_SETUP },
	{ "ls-files", cmd_ls_files, RUN_SETUP },
	{ "ls-remote", cmd_ls_remote, RUN_SETUP_GENTLY },
	{ "ls-tree", cmd_ls_tree, RUN_SETUP },
	{ "mailinfo", cmd_mailinfo, RUN_SETUP_GENTLY },
	{ "mailsplit", cmd_mailsplit, NO_PARSEOPT },
	{ "maintenance", cmd_maintenance, RUN_SETUP },
	{ "merge", cmd_merge, RUN_SETUP | NEED_WORK_TREE },
	{ "merge-base", cmd_merge_base, RUN_SETUP },
	{ "merge-file", cmd_merge_file, RUN_SETUP_GENTLY },
	{ "merge-index", cmd_merge_index, RUN_SETUP | NO_PARSEOPT },
	{ "merge-ours", cmd_merge_ours, RUN_SETUP | NO_PARSEOPT },
	{ "merge-recursive", cmd_merge_recursive, RUN_SETUP | NEED_WORK_TREE | NO_PARSEOPT },
	{ "merge-recursive-ours", cmd_merge_recursive, RUN_SETUP | NEED_WORK_TREE | NO_PARSEOPT },
	{ "merge-recursive-theirs", cmd_merge_recursive, RUN_SETUP | NEED_WORK_TREE | NO_PARSEOPT },
	{ "merge-subtree", cmd_merge_recursive, RUN_SETUP | NEED_WORK_TREE | NO_PARSEOPT },
	{ "merge-tree", cmd_merge_tree, RUN_SETUP },
	{ "mktag", cmd_mktag, RUN_SETUP },
	{ "mktree", cmd_mktree, RUN_SETUP },
	{ "multi-pack-index", cmd_multi_pack_index, RUN_SETUP },
	{ "mv", cmd_mv, RUN_SETUP | NEED_WORK_TREE },
	{ "name-rev", cmd_name_rev, RUN_SETUP },
	{ "notes", cmd_notes, RUN_SETUP },
	{ "pack-objects", cmd_pack_objects, RUN_SETUP },
	{ "pack-redundant", cmd_pack_redundant, RUN_SETUP | NO_PARSEOPT },
	{ "pack-refs", cmd_pack_refs, RUN_SETUP },
	{ "patch-id", cmd_patch_id, RUN_SETUP_GENTLY | NO_PARSEOPT },
	{ "pickaxe", cmd_blame, RUN_SETUP },
	{ "prune", cmd_prune, RUN_SETUP },
	{ "prune-packed", cmd_prune_packed, RUN_SETUP },
	{ "pull", cmd_pull, RUN_SETUP | NEED_WORK_TREE },
	{ "push", cmd_push, RUN_SETUP },
	{ "range-diff", cmd_range_diff, RUN_SETUP | USE_PAGER },
	{ "read-tree", cmd_read_tree, RUN_SETUP | SUPPORT_SUPER_PREFIX},
	{ "rebase", cmd_rebase, RUN_SETUP | NEED_WORK_TREE },
	{ "receive-pack", cmd_receive_pack },
	{ "reflog", cmd_reflog, RUN_SETUP },
	{ "remote", cmd_remote, RUN_SETUP },
	{ "remote-ext", cmd_remote_ext, NO_PARSEOPT },
	{ "remote-fd", cmd_remote_fd, NO_PARSEOPT },
	{ "repack", cmd_repack, RUN_SETUP },
	{ "replace", cmd_replace, RUN_SETUP },
	{ "rerere", cmd_rerere, RUN_SETUP },
	{ "reset", cmd_reset, RUN_SETUP },
	{ "restore", cmd_restore, RUN_SETUP | NEED_WORK_TREE },
	{ "rev-list", cmd_rev_list, RUN_SETUP | NO_PARSEOPT },
	{ "rev-parse", cmd_rev_parse, NO_PARSEOPT },
	{ "revert", cmd_revert, RUN_SETUP | NEED_WORK_TREE },
	{ "rm", cmd_rm, RUN_SETUP },
	{ "send-pack", cmd_send_pack, RUN_SETUP },
	{ "shortlog", cmd_shortlog, RUN_SETUP_GENTLY | USE_PAGER },
	{ "show", cmd_show, RUN_SETUP },
	{ "show-branch", cmd_show_branch, RUN_SETUP },
	{ "show-index", cmd_show_index, RUN_SETUP_GENTLY },
	{ "show-ref", cmd_show_ref, RUN_SETUP },
	{ "sparse-checkout", cmd_sparse_checkout, RUN_SETUP | NEED_WORK_TREE },
	{ "stage", cmd_add, RUN_SETUP | NEED_WORK_TREE },
	{ "stash", cmd_stash, RUN_SETUP | NEED_WORK_TREE },
	{ "status", cmd_status, RUN_SETUP | NEED_WORK_TREE },
	{ "stripspace", cmd_stripspace },
	{ "submodule--helper", cmd_submodule__helper, RUN_SETUP | SUPPORT_SUPER_PREFIX },
	{ "switch", cmd_switch, RUN_SETUP | NEED_WORK_TREE },
	{ "symbolic-ref", cmd_symbolic_ref, RUN_SETUP },
	{ "tag", cmd_tag, RUN_SETUP | DELAY_PAGER_CONFIG },
	{ "unpack-file", cmd_unpack_file, RUN_SETUP | NO_PARSEOPT },
	{ "unpack-objects", cmd_unpack_objects, RUN_SETUP | NO_PARSEOPT },
	{ "update-index", cmd_update_index, RUN_SETUP },
	{ "update-ref", cmd_update_ref, RUN_SETUP },
	{ "update-server-info", cmd_update_server_info, RUN_SETUP },
	{ "upload-archive", cmd_upload_archive, NO_PARSEOPT },
	{ "upload-archive--writer", cmd_upload_archive_writer, NO_PARSEOPT },
	{ "upload-pack", cmd_upload_pack },
	{ "var", cmd_var, RUN_SETUP_GENTLY | NO_PARSEOPT },
	{ "verify-commit", cmd_verify_commit, RUN_SETUP },
	{ "verify-pack", cmd_verify_pack },
	{ "verify-tag", cmd_verify_tag, RUN_SETUP },
	{ "version", cmd_version },
	{ "whatchanged", cmd_whatchanged, RUN_SETUP },
	{ "worktree", cmd_worktree, RUN_SETUP },
	{ "write-tree", cmd_write_tree, RUN_SETUP },
};

static struct cmd_struct *get_builtin(const char *s)
{
	int i;
	for (i = 0; i < ARRAY_SIZE(commands); i++) {
		struct cmd_struct *p = commands + i;
		if (!strcmp(s, p->cmd))
			return p;
	}
	return NULL;
}

int is_builtin(const char *s)
{
	return !!get_builtin(s);
}

static void list_builtins(struct string_list *out, unsigned int exclude_option)
{
	int i;
	for (i = 0; i < ARRAY_SIZE(commands); i++) {
		if (exclude_option &&
		    (commands[i].option & exclude_option))
			continue;
		string_list_append(out, commands[i].cmd);
	}
}

void load_builtin_commands(const char *prefix, struct cmdnames *cmds)
{
	const char *name;
	int i;

	/*
	 * Callers can ask for a subset of the commands based on a certain
	 * prefix, which is then dropped from the added names. The names in
	 * the `commands[]` array do not have the `git-` prefix, though,
	 * therefore we must expect the `prefix` to at least start with `git-`.
	 */
	if (!skip_prefix(prefix, "git-", &prefix))
		BUG("prefix '%s' must start with 'git-'", prefix);

	for (i = 0; i < ARRAY_SIZE(commands); i++)
		if (skip_prefix(commands[i].cmd, prefix, &name))
			add_cmdname(cmds, name, strlen(name));
}

#ifdef STRIP_EXTENSION
static void strip_extension(const char **argv)
{
	size_t len;

	if (strip_suffix(argv[0], STRIP_EXTENSION, &len))
		argv[0] = xmemdupz(argv[0], len);
}
#else
#define strip_extension(cmd)
#endif

static void handle_builtin(int argc, const char **argv)
{
	struct strvec args = STRVEC_INIT;
	const char *cmd;
	struct cmd_struct *builtin;

	strip_extension(argv);
	cmd = argv[0];

	/* Turn "git cmd --help" into "git help --exclude-guides cmd" */
	if (argc > 1 && !strcmp(argv[1], "--help")) {
		int i;

		argv[1] = argv[0];
		argv[0] = cmd = "help";

		for (i = 0; i < argc; i++) {
			strvec_push(&args, argv[i]);
			if (!i)
				strvec_push(&args, "--exclude-guides");
		}

		argc++;
		argv = args.v;
	}

	builtin = get_builtin(cmd);
	if (builtin)
		exit(run_builtin(builtin, argc, argv));
	strvec_clear(&args);
}

static void execv_dashed_external(const char **argv)
{
	struct child_process cmd = CHILD_PROCESS_INIT;
	int status;

	if (get_super_prefix())
		die(_("%s doesn't support --super-prefix"), argv[0]);

	if (use_pager == -1 && !is_builtin(argv[0]))
		use_pager = check_pager_config(argv[0]);
	commit_pager_choice();

	strvec_pushf(&cmd.args, "git-%s", argv[0]);
	strvec_pushv(&cmd.args, argv + 1);
	cmd.clean_on_exit = 1;
	cmd.wait_after_clean = 1;
	cmd.silent_exec_failure = 1;
	cmd.trace2_child_class = "dashed";

	trace2_cmd_name("_run_dashed_");

	/*
	 * The code in run_command() logs trace2 child_start/child_exit
	 * events, so we do not need to report exec/exec_result events here.
	 */
	trace_argv_printf(cmd.args.v, "trace: exec:");

	/*
	 * If we fail because the command is not found, it is
	 * OK to return. Otherwise, we just pass along the status code,
	 * or our usual generic code if we were not even able to exec
	 * the program.
	 */
	status = run_command(&cmd);

	/*
	 * If the child process ran and we are now going to exit, emit a
	 * generic string as our trace2 command verb to indicate that we
	 * launched a dashed command.
	 */
	if (status >= 0)
		exit(status);
	else if (errno != ENOENT)
		exit(128);
}

static int run_argv(int *argcp, const char ***argv)
{
	int done_alias = 0;
	struct string_list cmd_list = STRING_LIST_INIT_NODUP;
	struct string_list_item *seen;

	while (1) {
		/*
		 * If we tried alias and futzed with our environment,
		 * it no longer is safe to invoke builtins directly in
		 * general.  We have to spawn them as dashed externals.
		 *
		 * NEEDSWORK: if we can figure out cases
		 * where it is safe to do, we can avoid spawning a new
		 * process.
		 */
		if (!done_alias)
			handle_builtin(*argcp, *argv);
		else if (get_builtin(**argv)) {
			struct child_process cmd = CHILD_PROCESS_INIT;
			int i;

			/*
			 * The current process is committed to launching a
			 * child process to run the command named in (**argv)
			 * and exiting.  Log a generic string as the trace2
			 * command verb to indicate this.  Note that the child
			 * process will log the actual verb when it runs.
			 */
			trace2_cmd_name("_run_git_alias_");

			if (get_super_prefix())
				die("%s doesn't support --super-prefix", **argv);

			commit_pager_choice();

			strvec_push(&cmd.args, "git");
			for (i = 0; i < *argcp; i++)
				strvec_push(&cmd.args, (*argv)[i]);

			trace_argv_printf(cmd.args.v, "trace: exec:");

			/*
			 * if we fail because the command is not found, it is
			 * OK to return. Otherwise, we just pass along the status code.
			 */
			cmd.silent_exec_failure = 1;
			cmd.clean_on_exit = 1;
			cmd.wait_after_clean = 1;
			cmd.trace2_child_class = "git_alias";
			i = run_command(&cmd);
			if (i >= 0 || errno != ENOENT)
				exit(i);
			die("could not execute builtin %s", **argv);
		}

		/* .. then try the external ones */
		execv_dashed_external(*argv);

		seen = unsorted_string_list_lookup(&cmd_list, *argv[0]);
		if (seen) {
			int i;
			struct strbuf sb = STRBUF_INIT;
			for (i = 0; i < cmd_list.nr; i++) {
				struct string_list_item *item = &cmd_list.items[i];

				strbuf_addf(&sb, "\n  %s", item->string);
				if (item == seen)
					strbuf_addstr(&sb, " <==");
				else if (i == cmd_list.nr - 1)
					strbuf_addstr(&sb, " ==>");
			}
			die(_("alias loop detected: expansion of '%s' does"
			      " not terminate:%s"), cmd_list.items[0].string, sb.buf);
		}

		string_list_append(&cmd_list, *argv[0]);

		/*
		 * It could be an alias -- this works around the insanity
		 * of overriding "git log" with "git show" by having
		 * alias.log = show
		 */
		if (!handle_alias(argcp, argv))
			break;
		done_alias = 1;
	}

	string_list_clear(&cmd_list, 0);

	return done_alias;
}

int cmd_main(int argc, const char **argv)
{
	const char *cmd;
	int done_help = 0;

	cmd = argv[0];
	if (!cmd)
		cmd = "git-help";
	else {
		const char *slash = find_last_dir_sep(cmd);
		if (slash)
			cmd = slash + 1;
	}

	trace_command_performance(argv);

	/*
	 * "git-xxxx" is the same as "git xxxx", but we obviously:
	 *
	 *  - cannot take flags in between the "git" and the "xxxx".
	 *  - cannot execute it externally (since it would just do
	 *    the same thing over again)
	 *
	 * So we just directly call the builtin handler, and die if
	 * that one cannot handle it.
	 */
	if (skip_prefix(cmd, "git-", &cmd)) {
		argv[0] = cmd;
		handle_builtin(argc, argv);
		die(_("cannot handle %s as a builtin"), cmd);
	}

	/* Look for flags.. */
	argv++;
	argc--;
	handle_options(&argv, &argc, NULL);

	if (!argc) {
		/* The user didn't specify a command; give them help */
		commit_pager_choice();
		printf(_("usage: %s\n\n"), git_usage_string);
		list_common_cmds_help();
		printf("\n%s\n", _(git_more_info_string));
		exit(1);
	}

	if (!strcmp("--version", argv[0]) || !strcmp("-v", argv[0]))
		argv[0] = "version";
	else if (!strcmp("--help", argv[0]) || !strcmp("-h", argv[0]))
		argv[0] = "help";

	cmd = argv[0];

	/*
	 * We use PATH to find git commands, but we prepend some higher
	 * precedence paths: the "--exec-path" option, the GIT_EXEC_PATH
	 * environment, and the $(gitexecdir) from the Makefile at build
	 * time.
	 */
	setup_path();

	while (1) {
		int was_alias = run_argv(&argc, &argv);
		if (errno != ENOENT)
			break;
		if (was_alias) {
			fprintf(stderr, _("expansion of alias '%s' failed; "
					  "'%s' is not a git command\n"),
				cmd, argv[0]);
			exit(1);
		}
		if (!done_help) {
			cmd = argv[0] = help_unknown_cmd(cmd);
			done_help = 1;
		} else
			break;
	}

	fprintf(stderr, _("failed to run command '%s': %s\n"),
		cmd, strerror(errno));

	return 1;
}
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