Squashed 'third_party/git/' content from commit cb71568594

git-subtree-dir: third_party/git
git-subtree-split: cb715685942260375e1eb8153b0768a376e4ece7

1 files changed, 795 insertions, 0 deletions

diff --git a/help.c b/help.c
new file mode 100644
index 000000000000..5261d83ecf15
--- /dev/null
+++ b/help.c
@@ -0,0 +1,795 @@
+#include "cache.h"
+#include "config.h"
+#include "builtin.h"
+#include "exec-cmd.h"
+#include "run-command.h"
+#include "levenshtein.h"
+#include "help.h"
+#include "command-list.h"
+#include "string-list.h"
+#include "column.h"
+#include "version.h"
+#include "refs.h"
+#include "parse-options.h"
+
+struct category_description {
+	uint32_t category;
+	const char *desc;
+};
+static uint32_t common_mask =
+	CAT_init | CAT_worktree | CAT_info |
+	CAT_history | CAT_remote;
+static struct category_description common_categories[] = {
+	{ CAT_init, N_("start a working area (see also: git help tutorial)") },
+	{ CAT_worktree, N_("work on the current change (see also: git help everyday)") },
+	{ CAT_info, N_("examine the history and state (see also: git help revisions)") },
+	{ CAT_history, N_("grow, mark and tweak your common history") },
+	{ CAT_remote, N_("collaborate (see also: git help workflows)") },
+	{ 0, NULL }
+};
+static struct category_description main_categories[] = {
+	{ CAT_mainporcelain, N_("Main Porcelain Commands") },
+	{ CAT_ancillarymanipulators, N_("Ancillary Commands / Manipulators") },
+	{ CAT_ancillaryinterrogators, N_("Ancillary Commands / Interrogators") },
+	{ CAT_foreignscminterface, N_("Interacting with Others") },
+	{ CAT_plumbingmanipulators, N_("Low-level Commands / Manipulators") },
+	{ CAT_plumbinginterrogators, N_("Low-level Commands / Interrogators") },
+	{ CAT_synchingrepositories, N_("Low-level Commands / Synching Repositories") },
+	{ CAT_purehelpers, N_("Low-level Commands / Internal Helpers") },
+	{ 0, NULL }
+};
+
+static const char *drop_prefix(const char *name, uint32_t category)
+{
+	const char *new_name;
+
+	if (skip_prefix(name, "git-", &new_name))
+		return new_name;
+	if (category == CAT_guide && skip_prefix(name, "git", &new_name))
+		return new_name;
+	return name;
+
+}
+
+static void extract_cmds(struct cmdname_help **p_cmds, uint32_t mask)
+{
+	int i, nr = 0;
+	struct cmdname_help *cmds;
+
+	if (ARRAY_SIZE(command_list) == 0)
+		BUG("empty command_list[] is a sign of broken generate-cmdlist.sh");
+
+	ALLOC_ARRAY(cmds, ARRAY_SIZE(command_list) + 1);
+
+	for (i = 0; i < ARRAY_SIZE(command_list); i++) {
+		const struct cmdname_help *cmd = command_list + i;
+
+		if (!(cmd->category & mask))
+			continue;
+
+		cmds[nr] = *cmd;
+		cmds[nr].name = drop_prefix(cmd->name, cmd->category);
+
+		nr++;
+	}
+	cmds[nr].name = NULL;
+	*p_cmds = cmds;
+}
+
+static void print_command_list(const struct cmdname_help *cmds,
+			       uint32_t mask, int longest)
+{
+	int i;
+
+	for (i = 0; cmds[i].name; i++) {
+		if (cmds[i].category & mask) {
+			size_t len = strlen(cmds[i].name);
+			printf("   %s   ", cmds[i].name);
+			if (longest > len)
+				mput_char(' ', longest - len);
+			puts(_(cmds[i].help));
+		}
+	}
+}
+
+static int cmd_name_cmp(const void *elem1, const void *elem2)
+{
+	const struct cmdname_help *e1 = elem1;
+	const struct cmdname_help *e2 = elem2;
+
+	return strcmp(e1->name, e2->name);
+}
+
+static void print_cmd_by_category(const struct category_description *catdesc,
+				  int *longest_p)
+{
+	struct cmdname_help *cmds;
+	int longest = 0;
+	int i, nr = 0;
+	uint32_t mask = 0;
+
+	for (i = 0; catdesc[i].desc; i++)
+		mask |= catdesc[i].category;
+
+	extract_cmds(&cmds, mask);
+
+	for (i = 0; cmds[i].name; i++, nr++) {
+		if (longest < strlen(cmds[i].name))
+			longest = strlen(cmds[i].name);
+	}
+	QSORT(cmds, nr, cmd_name_cmp);
+
+	for (i = 0; catdesc[i].desc; i++) {
+		uint32_t mask = catdesc[i].category;
+		const char *desc = catdesc[i].desc;
+
+		printf("\n%s\n", _(desc));
+		print_command_list(cmds, mask, longest);
+	}
+	free(cmds);
+	if (longest_p)
+		*longest_p = longest;
+}
+
+void add_cmdname(struct cmdnames *cmds, const char *name, int len)
+{
+	struct cmdname *ent;
+	FLEX_ALLOC_MEM(ent, name, name, len);
+	ent->len = len;
+
+	ALLOC_GROW(cmds->names, cmds->cnt + 1, cmds->alloc);
+	cmds->names[cmds->cnt++] = ent;
+}
+
+static void clean_cmdnames(struct cmdnames *cmds)
+{
+	int i;
+	for (i = 0; i < cmds->cnt; ++i)
+		free(cmds->names[i]);
+	free(cmds->names);
+	cmds->cnt = 0;
+	cmds->alloc = 0;
+}
+
+static int cmdname_compare(const void *a_, const void *b_)
+{
+	struct cmdname *a = *(struct cmdname **)a_;
+	struct cmdname *b = *(struct cmdname **)b_;
+	return strcmp(a->name, b->name);
+}
+
+static void uniq(struct cmdnames *cmds)
+{
+	int i, j;
+
+	if (!cmds->cnt)
+		return;
+
+	for (i = j = 1; i < cmds->cnt; i++) {
+		if (!strcmp(cmds->names[i]->name, cmds->names[j-1]->name))
+			free(cmds->names[i]);
+		else
+			cmds->names[j++] = cmds->names[i];
+	}
+
+	cmds->cnt = j;
+}
+
+void exclude_cmds(struct cmdnames *cmds, struct cmdnames *excludes)
+{
+	int ci, cj, ei;
+	int cmp;
+
+	ci = cj = ei = 0;
+	while (ci < cmds->cnt && ei < excludes->cnt) {
+		cmp = strcmp(cmds->names[ci]->name, excludes->names[ei]->name);
+		if (cmp < 0)
+			cmds->names[cj++] = cmds->names[ci++];
+		else if (cmp == 0) {
+			ei++;
+			free(cmds->names[ci++]);
+		} else if (cmp > 0)
+			ei++;
+	}
+
+	while (ci < cmds->cnt)
+		cmds->names[cj++] = cmds->names[ci++];
+
+	cmds->cnt = cj;
+}
+
+static void pretty_print_cmdnames(struct cmdnames *cmds, unsigned int colopts)
+{
+	struct string_list list = STRING_LIST_INIT_NODUP;
+	struct column_options copts;
+	int i;
+
+	for (i = 0; i < cmds->cnt; i++)
+		string_list_append(&list, cmds->names[i]->name);
+	/*
+	 * always enable column display, we only consult column.*
+	 * about layout strategy and stuff
+	 */
+	colopts = (colopts & ~COL_ENABLE_MASK) | COL_ENABLED;
+	memset(&copts, 0, sizeof(copts));
+	copts.indent = "  ";
+	copts.padding = 2;
+	print_columns(&list, colopts, &copts);
+	string_list_clear(&list, 0);
+}
+
+static void list_commands_in_dir(struct cmdnames *cmds,
+					 const char *path,
+					 const char *prefix)
+{
+	DIR *dir = opendir(path);
+	struct dirent *de;
+	struct strbuf buf = STRBUF_INIT;
+	int len;
+
+	if (!dir)
+		return;
+	if (!prefix)
+		prefix = "git-";
+
+	strbuf_addf(&buf, "%s/", path);
+	len = buf.len;
+
+	while ((de = readdir(dir)) != NULL) {
+		const char *ent;
+		size_t entlen;
+
+		if (!skip_prefix(de->d_name, prefix, &ent))
+			continue;
+
+		strbuf_setlen(&buf, len);
+		strbuf_addstr(&buf, de->d_name);
+		if (!is_executable(buf.buf))
+			continue;
+
+		entlen = strlen(ent);
+		strip_suffix(ent, ".exe", &entlen);
+
+		add_cmdname(cmds, ent, entlen);
+	}
+	closedir(dir);
+	strbuf_release(&buf);
+}
+
+void load_command_list(const char *prefix,
+		struct cmdnames *main_cmds,
+		struct cmdnames *other_cmds)
+{
+	const char *env_path = getenv("PATH");
+	const char *exec_path = git_exec_path();
+
+	if (exec_path) {
+		list_commands_in_dir(main_cmds, exec_path, prefix);
+		QSORT(main_cmds->names, main_cmds->cnt, cmdname_compare);
+		uniq(main_cmds);
+	}
+
+	if (env_path) {
+		char *paths, *path, *colon;
+		path = paths = xstrdup(env_path);
+		while (1) {
+			if ((colon = strchr(path, PATH_SEP)))
+				*colon = 0;
+			if (!exec_path || strcmp(path, exec_path))
+				list_commands_in_dir(other_cmds, path, prefix);
+
+			if (!colon)
+				break;
+			path = colon + 1;
+		}
+		free(paths);
+
+		QSORT(other_cmds->names, other_cmds->cnt, cmdname_compare);
+		uniq(other_cmds);
+	}
+	exclude_cmds(other_cmds, main_cmds);
+}
+
+void list_commands(unsigned int colopts,
+		   struct cmdnames *main_cmds, struct cmdnames *other_cmds)
+{
+	if (main_cmds->cnt) {
+		const char *exec_path = git_exec_path();
+		printf_ln(_("available git commands in '%s'"), exec_path);
+		putchar('\n');
+		pretty_print_cmdnames(main_cmds, colopts);
+		putchar('\n');
+	}
+
+	if (other_cmds->cnt) {
+		printf_ln(_("git commands available from elsewhere on your $PATH"));
+		putchar('\n');
+		pretty_print_cmdnames(other_cmds, colopts);
+		putchar('\n');
+	}
+}
+
+void list_common_cmds_help(void)
+{
+	puts(_("These are common Git commands used in various situations:"));
+	print_cmd_by_category(common_categories, NULL);
+}
+
+void list_all_main_cmds(struct string_list *list)
+{
+	struct cmdnames main_cmds, other_cmds;
+	int i;
+
+	memset(&main_cmds, 0, sizeof(main_cmds));
+	memset(&other_cmds, 0, sizeof(other_cmds));
+	load_command_list("git-", &main_cmds, &other_cmds);
+
+	for (i = 0; i < main_cmds.cnt; i++)
+		string_list_append(list, main_cmds.names[i]->name);
+
+	clean_cmdnames(&main_cmds);
+	clean_cmdnames(&other_cmds);
+}
+
+void list_all_other_cmds(struct string_list *list)
+{
+	struct cmdnames main_cmds, other_cmds;
+	int i;
+
+	memset(&main_cmds, 0, sizeof(main_cmds));
+	memset(&other_cmds, 0, sizeof(other_cmds));
+	load_command_list("git-", &main_cmds, &other_cmds);
+
+	for (i = 0; i < other_cmds.cnt; i++)
+		string_list_append(list, other_cmds.names[i]->name);
+
+	clean_cmdnames(&main_cmds);
+	clean_cmdnames(&other_cmds);
+}
+
+void list_cmds_by_category(struct string_list *list,
+			   const char *cat)
+{
+	int i, n = ARRAY_SIZE(command_list);
+	uint32_t cat_id = 0;
+
+	for (i = 0; category_names[i]; i++) {
+		if (!strcmp(cat, category_names[i])) {
+			cat_id = 1UL << i;
+			break;
+		}
+	}
+	if (!cat_id)
+		die(_("unsupported command listing type '%s'"), cat);
+
+	for (i = 0; i < n; i++) {
+		struct cmdname_help *cmd = command_list + i;
+
+		if (!(cmd->category & cat_id))
+			continue;
+		string_list_append(list, drop_prefix(cmd->name, cmd->category));
+	}
+}
+
+void list_cmds_by_config(struct string_list *list)
+{
+	const char *cmd_list;
+
+	if (git_config_get_string_const("completion.commands", &cmd_list))
+		return;
+
+	string_list_sort(list);
+	string_list_remove_duplicates(list, 0);
+
+	while (*cmd_list) {
+		struct strbuf sb = STRBUF_INIT;
+		const char *p = strchrnul(cmd_list, ' ');
+
+		strbuf_add(&sb, cmd_list, p - cmd_list);
+		if (sb.buf[0] == '-')
+			string_list_remove(list, sb.buf + 1, 0);
+		else
+			string_list_insert(list, sb.buf);
+		strbuf_release(&sb);
+		while (*p == ' ')
+			p++;
+		cmd_list = p;
+	}
+}
+
+void list_common_guides_help(void)
+{
+	struct category_description catdesc[] = {
+		{ CAT_guide, N_("The common Git guides are:") },
+		{ 0, NULL }
+	};
+	print_cmd_by_category(catdesc, NULL);
+	putchar('\n');
+}
+
+struct slot_expansion {
+	const char *prefix;
+	const char *placeholder;
+	void (*fn)(struct string_list *list, const char *prefix);
+	int found;
+};
+
+void list_config_help(int for_human)
+{
+	struct slot_expansion slot_expansions[] = {
+		{ "advice", "*", list_config_advices },
+		{ "color.branch", "<slot>", list_config_color_branch_slots },
+		{ "color.decorate", "<slot>", list_config_color_decorate_slots },
+		{ "color.diff", "<slot>", list_config_color_diff_slots },
+		{ "color.grep", "<slot>", list_config_color_grep_slots },
+		{ "color.interactive", "<slot>", list_config_color_interactive_slots },
+		{ "color.remote", "<slot>", list_config_color_sideband_slots },
+		{ "color.status", "<slot>", list_config_color_status_slots },
+		{ "fsck", "<msg-id>", list_config_fsck_msg_ids },
+		{ "receive.fsck", "<msg-id>", list_config_fsck_msg_ids },
+		{ NULL, NULL, NULL }
+	};
+	const char **p;
+	struct slot_expansion *e;
+	struct string_list keys = STRING_LIST_INIT_DUP;
+	int i;
+
+	for (p = config_name_list; *p; p++) {
+		const char *var = *p;
+		struct strbuf sb = STRBUF_INIT;
+
+		for (e = slot_expansions; e->prefix; e++) {
+
+			strbuf_reset(&sb);
+			strbuf_addf(&sb, "%s.%s", e->prefix, e->placeholder);
+			if (!strcasecmp(var, sb.buf)) {
+				e->fn(&keys, e->prefix);
+				e->found++;
+				break;
+			}
+		}
+		strbuf_release(&sb);
+		if (!e->prefix)
+			string_list_append(&keys, var);
+	}
+
+	for (e = slot_expansions; e->prefix; e++)
+		if (!e->found)
+			BUG("slot_expansion %s.%s is not used",
+			    e->prefix, e->placeholder);
+
+	string_list_sort(&keys);
+	for (i = 0; i < keys.nr; i++) {
+		const char *var = keys.items[i].string;
+		const char *wildcard, *tag, *cut;
+
+		if (for_human) {
+			puts(var);
+			continue;
+		}
+
+		wildcard = strchr(var, '*');
+		tag = strchr(var, '<');
+
+		if (!wildcard && !tag) {
+			puts(var);
+			continue;
+		}
+
+		if (wildcard && !tag)
+			cut = wildcard;
+		else if (!wildcard && tag)
+			cut = tag;
+		else
+			cut = wildcard < tag ? wildcard : tag;
+
+		/*
+		 * We may produce duplicates, but that's up to
+		 * git-completion.bash to handle
+		 */
+		printf("%.*s\n", (int)(cut - var), var);
+	}
+	string_list_clear(&keys, 0);
+}
+
+static int get_alias(const char *var, const char *value, void *data)
+{
+	struct string_list *list = data;
+
+	if (skip_prefix(var, "alias.", &var))
+		string_list_append(list, var)->util = xstrdup(value);
+
+	return 0;
+}
+
+void list_all_cmds_help(void)
+{
+	struct string_list others = STRING_LIST_INIT_DUP;
+	struct string_list alias_list = STRING_LIST_INIT_DUP;
+	struct cmdname_help *aliases;
+	int i, longest;
+
+	printf_ln(_("See 'git help <command>' to read about a specific subcommand"));
+	print_cmd_by_category(main_categories, &longest);
+
+	list_all_other_cmds(&others);
+	if (others.nr)
+		printf("\n%s\n", _("External commands"));
+	for (i = 0; i < others.nr; i++)
+		printf("   %s\n", others.items[i].string);
+	string_list_clear(&others, 0);
+
+	git_config(get_alias, &alias_list);
+	string_list_sort(&alias_list);
+
+	for (i = 0; i < alias_list.nr; i++) {
+		size_t len = strlen(alias_list.items[i].string);
+		if (longest < len)
+			longest = len;
+	}
+
+	if (alias_list.nr) {
+		printf("\n%s\n", _("Command aliases"));
+		ALLOC_ARRAY(aliases, alias_list.nr + 1);
+		for (i = 0; i < alias_list.nr; i++) {
+			aliases[i].name = alias_list.items[i].string;
+			aliases[i].help = alias_list.items[i].util;
+			aliases[i].category = 1;
+		}
+		aliases[alias_list.nr].name = NULL;
+		print_command_list(aliases, 1, longest);
+		free(aliases);
+	}
+	string_list_clear(&alias_list, 1);
+}
+
+int is_in_cmdlist(struct cmdnames *c, const char *s)
+{
+	int i;
+	for (i = 0; i < c->cnt; i++)
+		if (!strcmp(s, c->names[i]->name))
+			return 1;
+	return 0;
+}
+
+static int autocorrect;
+static struct cmdnames aliases;
+
+static int git_unknown_cmd_config(const char *var, const char *value, void *cb)
+{
+	const char *p;
+
+	if (!strcmp(var, "help.autocorrect"))
+		autocorrect = git_config_int(var,value);
+	/* Also use aliases for command lookup */
+	if (skip_prefix(var, "alias.", &p))
+		add_cmdname(&aliases, p, strlen(p));
+
+	return git_default_config(var, value, cb);
+}
+
+static int levenshtein_compare(const void *p1, const void *p2)
+{
+	const struct cmdname *const *c1 = p1, *const *c2 = p2;
+	const char *s1 = (*c1)->name, *s2 = (*c2)->name;
+	int l1 = (*c1)->len;
+	int l2 = (*c2)->len;
+	return l1 != l2 ? l1 - l2 : strcmp(s1, s2);
+}
+
+static void add_cmd_list(struct cmdnames *cmds, struct cmdnames *old)
+{
+	int i;
+	ALLOC_GROW(cmds->names, cmds->cnt + old->cnt, cmds->alloc);
+
+	for (i = 0; i < old->cnt; i++)
+		cmds->names[cmds->cnt++] = old->names[i];
+	FREE_AND_NULL(old->names);
+	old->cnt = 0;
+}
+
+/* An empirically derived magic number */
+#define SIMILARITY_FLOOR 7
+#define SIMILAR_ENOUGH(x) ((x) < SIMILARITY_FLOOR)
+
+static const char bad_interpreter_advice[] =
+	N_("'%s' appears to be a git command, but we were not\n"
+	"able to execute it. Maybe git-%s is broken?");
+
+const char *help_unknown_cmd(const char *cmd)
+{
+	int i, n, best_similarity = 0;
+	struct cmdnames main_cmds, other_cmds;
+	struct cmdname_help *common_cmds;
+
+	memset(&main_cmds, 0, sizeof(main_cmds));
+	memset(&other_cmds, 0, sizeof(other_cmds));
+	memset(&aliases, 0, sizeof(aliases));
+
+	read_early_config(git_unknown_cmd_config, NULL);
+
+	load_command_list("git-", &main_cmds, &other_cmds);
+
+	add_cmd_list(&main_cmds, &aliases);
+	add_cmd_list(&main_cmds, &other_cmds);
+	QSORT(main_cmds.names, main_cmds.cnt, cmdname_compare);
+	uniq(&main_cmds);
+
+	extract_cmds(&common_cmds, common_mask);
+
+	/* This abuses cmdname->len for levenshtein distance */
+	for (i = 0, n = 0; i < main_cmds.cnt; i++) {
+		int cmp = 0; /* avoid compiler stupidity */
+		const char *candidate = main_cmds.names[i]->name;
+
+		/*
+		 * An exact match means we have the command, but
+		 * for some reason exec'ing it gave us ENOENT; probably
+		 * it's a bad interpreter in the #! line.
+		 */
+		if (!strcmp(candidate, cmd))
+			die(_(bad_interpreter_advice), cmd, cmd);
+
+		/* Does the candidate appear in common_cmds list? */
+		while (common_cmds[n].name &&
+		       (cmp = strcmp(common_cmds[n].name, candidate)) < 0)
+			n++;
+		if (common_cmds[n].name && !cmp) {
+			/* Yes, this is one of the common commands */
+			n++; /* use the entry from common_cmds[] */
+			if (starts_with(candidate, cmd)) {
+				/* Give prefix match a very good score */
+				main_cmds.names[i]->len = 0;
+				continue;
+			}
+		}
+
+		main_cmds.names[i]->len =
+			levenshtein(cmd, candidate, 0, 2, 1, 3) + 1;
+	}
+	FREE_AND_NULL(common_cmds);
+
+	QSORT(main_cmds.names, main_cmds.cnt, levenshtein_compare);
+
+	if (!main_cmds.cnt)
+		die(_("Uh oh. Your system reports no Git commands at all."));
+
+	/* skip and count prefix matches */
+	for (n = 0; n < main_cmds.cnt && !main_cmds.names[n]->len; n++)
+		; /* still counting */
+
+	if (main_cmds.cnt <= n) {
+		/* prefix matches with everything? that is too ambiguous */
+		best_similarity = SIMILARITY_FLOOR + 1;
+	} else {
+		/* count all the most similar ones */
+		for (best_similarity = main_cmds.names[n++]->len;
+		     (n < main_cmds.cnt &&
+		      best_similarity == main_cmds.names[n]->len);
+		     n++)
+			; /* still counting */
+	}
+	if (autocorrect && n == 1 && SIMILAR_ENOUGH(best_similarity)) {
+		const char *assumed = main_cmds.names[0]->name;
+		main_cmds.names[0] = NULL;
+		clean_cmdnames(&main_cmds);
+		fprintf_ln(stderr,
+			   _("WARNING: You called a Git command named '%s', "
+			     "which does not exist."),
+			   cmd);
+		if (autocorrect < 0)
+			fprintf_ln(stderr,
+				   _("Continuing under the assumption that "
+				     "you meant '%s'."),
+				   assumed);
+		else {
+			fprintf_ln(stderr,
+				   _("Continuing in %0.1f seconds, "
+				     "assuming that you meant '%s'."),
+				   (float)autocorrect/10.0, assumed);
+			sleep_millisec(autocorrect * 100);
+		}
+		return assumed;
+	}
+
+	fprintf_ln(stderr, _("git: '%s' is not a git command. See 'git --help'."), cmd);
+
+	if (SIMILAR_ENOUGH(best_similarity)) {
+		fprintf_ln(stderr,
+			   Q_("\nThe most similar command is",
+			      "\nThe most similar commands are",
+			   n));
+
+		for (i = 0; i < n; i++)
+			fprintf(stderr, "\t%s\n", main_cmds.names[i]->name);
+	}
+
+	exit(1);
+}
+
+int cmd_version(int argc, const char **argv, const char *prefix)
+{
+	int build_options = 0;
+	const char * const usage[] = {
+		N_("git version [<options>]"),
+		NULL
+	};
+	struct option options[] = {
+		OPT_BOOL(0, "build-options", &build_options,
+			 "also print build options"),
+		OPT_END()
+	};
+
+	argc = parse_options(argc, argv, prefix, options, usage, 0);
+
+	/*
+	 * The format of this string should be kept stable for compatibility
+	 * with external projects that rely on the output of "git version".
+	 *
+	 * Always show the version, even if other options are given.
+	 */
+	printf("git version %s\n", git_version_string);
+
+	if (build_options) {
+		printf("cpu: %s\n", GIT_HOST_CPU);
+		if (git_built_from_commit_string[0])
+			printf("built from commit: %s\n",
+			       git_built_from_commit_string);
+		else
+			printf("no commit associated with this build\n");
+		printf("sizeof-long: %d\n", (int)sizeof(long));
+		printf("sizeof-size_t: %d\n", (int)sizeof(size_t));
+		/* NEEDSWORK: also save and output GIT-BUILD_OPTIONS? */
+	}
+	return 0;
+}
+
+struct similar_ref_cb {
+	const char *base_ref;
+	struct string_list *similar_refs;
+};
+
+static int append_similar_ref(const char *refname, const struct object_id *oid,
+			      int flags, void *cb_data)
+{
+	struct similar_ref_cb *cb = (struct similar_ref_cb *)(cb_data);
+	char *branch = strrchr(refname, '/') + 1;
+
+	/* A remote branch of the same name is deemed similar */
+	if (starts_with(refname, "refs/remotes/") &&
+	    !strcmp(branch, cb->base_ref))
+		string_list_append_nodup(cb->similar_refs,
+					 shorten_unambiguous_ref(refname, 1));
+	return 0;
+}
+
+static struct string_list guess_refs(const char *ref)
+{
+	struct similar_ref_cb ref_cb;
+	struct string_list similar_refs = STRING_LIST_INIT_DUP;
+
+	ref_cb.base_ref = ref;
+	ref_cb.similar_refs = &similar_refs;
+	for_each_ref(append_similar_ref, &ref_cb);
+	return similar_refs;
+}
+
+void help_unknown_ref(const char *ref, const char *cmd, const char *error)
+{
+	int i;
+	struct string_list suggested_refs = guess_refs(ref);
+
+	fprintf_ln(stderr, _("%s: %s - %s"), cmd, ref, error);
+
+	if (suggested_refs.nr > 0) {
+		fprintf_ln(stderr,
+			   Q_("\nDid you mean this?",
+			      "\nDid you mean one of these?",
+			      suggested_refs.nr));
+		for (i = 0; i < suggested_refs.nr; i++)
+			fprintf(stderr, "\t%s\n", suggested_refs.items[i].string);
+	}
+
+	string_list_clear(&suggested_refs, 0);
+	exit(1);
+}