git/builtin/grep.c

/*
 * Builtin "git grep"
 *
 * Copyright (c) 2006 Junio C Hamano
 */
#define USE_THE_INDEX_COMPATIBILITY_MACROS
#include "cache.h"
#include "repository.h"
#include "config.h"
#include "blob.h"
#include "tree.h"
#include "commit.h"
#include "tag.h"
#include "tree-walk.h"
#include "builtin.h"
#include "parse-options.h"
#include "string-list.h"
#include "run-command.h"
#include "userdiff.h"
#include "grep.h"
#include "quote.h"
#include "dir.h"
#include "pathspec.h"
#include "submodule.h"
#include "submodule-config.h"
#include "object-store.h"
#include "packfile.h"

static const char *grep_prefix;

static char const * const grep_usage[] = {
	N_("git grep [<options>] [-e] <pattern> [<rev>...] [[--] <path>...]"),
	NULL
};

static int recurse_submodules;

static int num_threads;

static pthread_t *threads;

/* We use one producer thread and THREADS consumer
 * threads. The producer adds struct work_items to 'todo' and the
 * consumers pick work items from the same array.
 */
struct work_item {
	struct grep_source source;
	char done;
	struct strbuf out;
};

/* In the range [todo_done, todo_start) in 'todo' we have work_items
 * that have been or are processed by a consumer thread. We haven't
 * written the result for these to stdout yet.
 *
 * The work_items in [todo_start, todo_end) are waiting to be picked
 * up by a consumer thread.
 *
 * The ranges are modulo TODO_SIZE.
 */
#define TODO_SIZE 128
static struct work_item todo[TODO_SIZE];
static int todo_start;
static int todo_end;
static int todo_done;

/* Has all work items been added? */
static int all_work_added;

static struct repository **repos_to_free;
static size_t repos_to_free_nr, repos_to_free_alloc;

/* This lock protects all the variables above. */
static pthread_mutex_t grep_mutex;

static inline void grep_lock(void)
{
	pthread_mutex_lock(&grep_mutex);
}

static inline void grep_unlock(void)
{
	pthread_mutex_unlock(&grep_mutex);
}

/* Signalled when a new work_item is added to todo. */
static pthread_cond_t cond_add;

/* Signalled when the result from one work_item is written to
 * stdout.
 */
static pthread_cond_t cond_write;

/* Signalled when we are finished with everything. */
static pthread_cond_t cond_result;

static int skip_first_line;

static void add_work(struct grep_opt *opt, struct grep_source *gs)
{
	if (opt->binary != GREP_BINARY_TEXT)
		grep_source_load_driver(gs, opt->repo->index);

	grep_lock();

	while ((todo_end+1) % ARRAY_SIZE(todo) == todo_done) {
		pthread_cond_wait(&cond_write, &grep_mutex);
	}

	todo[todo_end].source = *gs;
	todo[todo_end].done = 0;
	strbuf_reset(&todo[todo_end].out);
	todo_end = (todo_end + 1) % ARRAY_SIZE(todo);

	pthread_cond_signal(&cond_add);
	grep_unlock();
}

static struct work_item *get_work(void)
{
	struct work_item *ret;

	grep_lock();
	while (todo_start == todo_end && !all_work_added) {
		pthread_cond_wait(&cond_add, &grep_mutex);
	}

	if (todo_start == todo_end && all_work_added) {
		ret = NULL;
	} else {
		ret = &todo[todo_start];
		todo_start = (todo_start + 1) % ARRAY_SIZE(todo);
	}
	grep_unlock();
	return ret;
}

static void work_done(struct work_item *w)
{
	int old_done;

	grep_lock();
	w->done = 1;
	old_done = todo_done;
	for(; todo[todo_done].done && todo_done != todo_start;
	    todo_done = (todo_done+1) % ARRAY_SIZE(todo)) {
		w = &todo[todo_done];
		if (w->out.len) {
			const char *p = w->out.buf;
			size_t len = w->out.len;

			/* Skip the leading hunk mark of the first file. */
			if (skip_first_line) {
				while (len) {
					len--;
					if (*p++ == '\n')
						break;
				}
				skip_first_line = 0;
			}

			write_or_die(1, p, len);
		}
		grep_source_clear(&w->source);
	}

	if (old_done != todo_done)
		pthread_cond_signal(&cond_write);

	if (all_work_added && todo_done == todo_end)
		pthread_cond_signal(&cond_result);

	grep_unlock();
}

static void free_repos(void)
{
	int i;

	for (i = 0; i < repos_to_free_nr; i++) {
		repo_clear(repos_to_free[i]);
		free(repos_to_free[i]);
	}
	FREE_AND_NULL(repos_to_free);
	repos_to_free_nr = 0;
	repos_to_free_alloc = 0;
}

static void *run(void *arg)
{
	int hit = 0;
	struct grep_opt *opt = arg;

	while (1) {
		struct work_item *w = get_work();
		if (!w)
			break;

		opt->output_priv = w;
		hit |= grep_source(opt, &w->source);
		grep_source_clear_data(&w->source);
		work_done(w);
	}
	free_grep_patterns(opt);
	free(opt);

	return (void*) (intptr_t) hit;
}

static void strbuf_out(struct grep_opt *opt, const void *buf, size_t size)
{
	struct work_item *w = opt->output_priv;
	strbuf_add(&w->out, buf, size);
}

static void start_threads(struct grep_opt *opt)
{
	int i;

	pthread_mutex_init(&grep_mutex, NULL);
	pthread_mutex_init(&grep_attr_mutex, NULL);
	pthread_cond_init(&cond_add, NULL);
	pthread_cond_init(&cond_write, NULL);
	pthread_cond_init(&cond_result, NULL);
	grep_use_locks = 1;
	enable_obj_read_lock();

	for (i = 0; i < ARRAY_SIZE(todo); i++) {
		strbuf_init(&todo[i].out, 0);
	}

	CALLOC_ARRAY(threads, num_threads);
	for (i = 0; i < num_threads; i++) {
		int err;
		struct grep_opt *o = grep_opt_dup(opt);
		o->output = strbuf_out;
		compile_grep_patterns(o);
		err = pthread_create(&threads[i], NULL, run, o);

		if (err)
			die(_("grep: failed to create thread: %s"),
			    strerror(err));
	}
}

static int wait_all(void)
{
	int hit = 0;
	int i;

	if (!HAVE_THREADS)
		BUG("Never call this function unless you have started threads");

	grep_lock();
	all_work_added = 1;

	/* Wait until all work is done. */
	while (todo_done != todo_end)
		pthread_cond_wait(&cond_result, &grep_mutex);

	/* Wake up all the consumer threads so they can see that there
	 * is no more work to do.
	 */
	pthread_cond_broadcast(&cond_add);
	grep_unlock();

	for (i = 0; i < num_threads; i++) {
		void *h;
		pthread_join(threads[i], &h);
		hit |= (int) (intptr_t) h;
	}

	free(threads);

	pthread_mutex_destroy(&grep_mutex);
	pthread_mutex_destroy(&grep_attr_mutex);
	pthread_cond_destroy(&cond_add);
	pthread_cond_destroy(&cond_write);
	pthread_cond_destroy(&cond_result);
	grep_use_locks = 0;
	disable_obj_read_lock();

	return hit;
}

static int grep_cmd_config(const char *var, const char *value, void *cb)
{
	int st = grep_config(var, value, cb);
	if (git_color_default_config(var, value, NULL) < 0)
		st = -1;

	if (!strcmp(var, "grep.threads")) {
		num_threads = git_config_int(var, value);
		if (num_threads < 0)
			die(_("invalid number of threads specified (%d) for %s"),
			    num_threads, var);
		else if (!HAVE_THREADS && num_threads > 1) {
			/*
			 * TRANSLATORS: %s is the configuration
			 * variable for tweaking threads, currently
			 * grep.threads
			 */
			warning(_("no threads support, ignoring %s"), var);
			num_threads = 1;
		}
	}

	if (!strcmp(var, "submodule.recurse"))
		recurse_submodules = git_config_bool(var, value);

	return st;
}

static void grep_source_name(struct grep_opt *opt, const char *filename,
			     int tree_name_len, struct strbuf *out)
{
	strbuf_reset(out);

	if (opt->null_following_name) {
		if (opt->relative && grep_prefix) {
			struct strbuf rel_buf = STRBUF_INIT;
			const char *rel_name =
				relative_path(filename + tree_name_len,
					      grep_prefix, &rel_buf);

			if (tree_name_len)
				strbuf_add(out, filename, tree_name_len);

			strbuf_addstr(out, rel_name);
			strbuf_release(&rel_buf);
		} else {
			strbuf_addstr(out, filename);
		}
		return;
	}

	if (opt->relative && grep_prefix)
		quote_path(filename + tree_name_len, grep_prefix, out, 0);
	else
		quote_c_style(filename + tree_name_len, out, NULL, 0);

	if (tree_name_len)
		strbuf_insert(out, 0, filename, tree_name_len);
}

static int grep_oid(struct grep_opt *opt, const struct object_id *oid,
		     const char *filename, int tree_name_len,
		     const char *path)
{
	struct strbuf pathbuf = STRBUF_INIT;
	struct grep_source gs;

	grep_source_name(opt, filename, tree_name_len, &pathbuf);
	grep_source_init_oid(&gs, pathbuf.buf, path, oid, opt->repo);
	strbuf_release(&pathbuf);

	if (num_threads > 1) {
		/*
		 * add_work() copies gs and thus assumes ownership of
		 * its fields, so do not call grep_source_clear()
		 */
		add_work(opt, &gs);
		return 0;
	} else {
		int hit;

		hit = grep_source(opt, &gs);

		grep_source_clear(&gs);
		return hit;
	}
}

static int grep_file(struct grep_opt *opt, const char *filename)
{
	struct strbuf buf = STRBUF_INIT;
	struct grep_source gs;

	grep_source_name(opt, filename, 0, &buf);
	grep_source_init_file(&gs, buf.buf, filename);
	strbuf_release(&buf);

	if (num_threads > 1) {
		/*
		 * add_work() copies gs and thus assumes ownership of
		 * its fields, so do not call grep_source_clear()
		 */
		add_work(opt, &gs);
		return 0;
	} else {
		int hit;

		hit = grep_source(opt, &gs);

		grep_source_clear(&gs);
		return hit;
	}
}

static void append_path(struct grep_opt *opt, const void *data, size_t len)
{
	struct string_list *path_list = opt->output_priv;

	if (len == 1 && *(const char *)data == '\0')
		return;
	string_list_append_nodup(path_list, xstrndup(data, len));
}

static void run_pager(struct grep_opt *opt, const char *prefix)
{
	struct string_list *path_list = opt->output_priv;
	struct child_process child = CHILD_PROCESS_INIT;
	int i, status;

	for (i = 0; i < path_list->nr; i++)
		strvec_push(&child.args, path_list->items[i].string);
	child.dir = prefix;
	child.use_shell = 1;

	status = run_command(&child);
	if (status)
		exit(status);
}

static int grep_cache(struct grep_opt *opt,
		      const struct pathspec *pathspec, int cached);
static int grep_tree(struct grep_opt *opt, const struct pathspec *pathspec,
		     struct tree_desc *tree, struct strbuf *base, int tn_len,
		     int check_attr);

static int grep_submodule(struct grep_opt *opt,
			  const struct pathspec *pathspec,
			  const struct object_id *oid,
			  const char *filename, const char *path, int cached)
{
	struct repository *subrepo;
	struct repository *superproject = opt->repo;
	struct grep_opt subopt;
	int hit = 0;

	if (!is_submodule_active(superproject, path))
		return 0;

	subrepo = xmalloc(sizeof(*subrepo));
	if (repo_submodule_init(subrepo, superproject, path, null_oid())) {
		free(subrepo);
		return 0;
	}
	ALLOC_GROW(repos_to_free, repos_to_free_nr + 1, repos_to_free_alloc);
	repos_to_free[repos_to_free_nr++] = subrepo;

	/*
	 * NEEDSWORK: repo_read_gitmodules() might call
	 * add_to_alternates_memory() via config_from_gitmodules(). This
	 * operation causes a race condition with concurrent object readings
	 * performed by the worker threads. That's why we need obj_read_lock()
	 * here. It should be removed once it's no longer necessary to add the
	 * subrepo's odbs to the in-memory alternates list.
	 */
	obj_read_lock();

	/*
	 * NEEDSWORK: when reading a submodule, the sparsity settings in the
	 * superproject are incorrectly forgotten or misused. For example:
	 *
	 * 1. "command_requires_full_index"
	 * 	When this setting is turned on for `grep`, only the superproject
	 *	knows it. All the submodules are read with their own configs
	 *	and get prepare_repo_settings()'d. Therefore, these submodules
	 *	"forget" the sparse-index feature switch. As a result, the index
	 *	of these submodules are expanded unexpectedly.
	 *
	 * 2. "core_apply_sparse_checkout"
	 *	When running `grep` in the superproject, this setting is
	 *	populated using the superproject's configs. However, once
	 *	initialized, this config is globally accessible and is read by
	 *	prepare_repo_settings() for the submodules. For instance, if a
	 *	submodule is using a sparse-checkout, however, the superproject
	 *	is not, the result is that the config from the superproject will
	 *	dictate the behavior for the submodule, making it "forget" its
	 *	sparse-checkout state.
	 *
	 * 3. "core_sparse_checkout_cone"
	 *	ditto.
	 *
	 * Note that this list is not exhaustive.
	 */
	repo_read_gitmodules(subrepo, 0);

	/*
	 * All code paths tested by test code no longer need submodule ODBs to
	 * be added as alternates, but add it to the list just in case.
	 * Submodule ODBs added through add_submodule_odb_by_path() will be
	 * lazily registered as alternates when needed (and except in an
	 * unexpected code interaction, it won't be needed).
	 */
	add_submodule_odb_by_path(subrepo->objects->odb->path);
	obj_read_unlock();

	memcpy(&subopt, opt, sizeof(subopt));
	subopt.repo = subrepo;

	if (oid) {
		enum object_type object_type;
		struct tree_desc tree;
		void *data;
		unsigned long size;
		struct strbuf base = STRBUF_INIT;

		obj_read_lock();
		object_type = oid_object_info(subrepo, oid, NULL);
		obj_read_unlock();
		data = read_object_with_reference(subrepo,
						  oid, OBJ_TREE,
						  &size, NULL);
		if (!data)
			die(_("unable to read tree (%s)"), oid_to_hex(oid));

		strbuf_addstr(&base, filename);
		strbuf_addch(&base, '/');

		init_tree_desc(&tree, data, size);
		hit = grep_tree(&subopt, pathspec, &tree, &base, base.len,
				object_type == OBJ_COMMIT);
		strbuf_release(&base);
		free(data);
	} else {
		hit = grep_cache(&subopt, pathspec, cached);
	}

	return hit;
}

static int grep_cache(struct grep_opt *opt,
		      const struct pathspec *pathspec, int cached)
{
	struct repository *repo = opt->repo;
	int hit = 0;
	int nr;
	struct strbuf name = STRBUF_INIT;
	int name_base_len = 0;
	if (repo->submodule_prefix) {
		name_base_len = strlen(repo->submodule_prefix);
		strbuf_addstr(&name, repo->submodule_prefix);
	}

	if (repo_read_index(repo) < 0)
		die(_("index file corrupt"));

	for (nr = 0; nr < repo->index->cache_nr; nr++) {
		const struct cache_entry *ce = repo->index->cache[nr];

		if (!cached && ce_skip_worktree(ce))
			continue;

		strbuf_setlen(&name, name_base_len);
		strbuf_addstr(&name, ce->name);
		if (S_ISSPARSEDIR(ce->ce_mode)) {
			enum object_type type;
			struct tree_desc tree;
			void *data;
			unsigned long size;

			data = read_object_file(&ce->oid, &type, &size);
			init_tree_desc(&tree, data, size);

			hit |= grep_tree(opt, pathspec, &tree, &name, 0, 0);
			strbuf_setlen(&name, name_base_len);
			strbuf_addstr(&name, ce->name);
			free(data);
		} else if (S_ISREG(ce->ce_mode) &&
		    match_pathspec(repo->index, pathspec, name.buf, name.len, 0, NULL,
				   S_ISDIR(ce->ce_mode) ||
				   S_ISGITLINK(ce->ce_mode))) {
			/*
			 * If CE_VALID is on, we assume worktree file and its
			 * cache entry are identical, even if worktree file has
			 * been modified, so use cache version instead
			 */
			if (cached || (ce->ce_flags & CE_VALID)) {
				if (ce_stage(ce) || ce_intent_to_add(ce))
					continue;
				hit |= grep_oid(opt, &ce->oid, name.buf,
						 0, name.buf);
			} else {
				hit |= grep_file(opt, name.buf);
			}
		} else if (recurse_submodules && S_ISGITLINK(ce->ce_mode) &&
			   submodule_path_match(repo->index, pathspec, name.buf, NULL)) {
			hit |= grep_submodule(opt, pathspec, NULL, ce->name,
					      ce->name, cached);
		} else {
			continue;
		}

		if (ce_stage(ce)) {
			do {
				nr++;
			} while (nr < repo->index->cache_nr &&
				 !strcmp(ce->name, repo->index->cache[nr]->name));
			nr--; /* compensate for loop control */
		}
		if (hit && opt->status_only)
			break;
	}

	strbuf_release(&name);
	return hit;
}

static int grep_tree(struct grep_opt *opt, const struct pathspec *pathspec,
		     struct tree_desc *tree, struct strbuf *base, int tn_len,
		     int check_attr)
{
	struct repository *repo = opt->repo;
	int hit = 0;
	enum interesting match = entry_not_interesting;
	struct name_entry entry;
	int old_baselen = base->len;
	struct strbuf name = STRBUF_INIT;
	int name_base_len = 0;
	if (repo->submodule_prefix) {
		strbuf_addstr(&name, repo->submodule_prefix);
		name_base_len = name.len;
	}

	while (tree_entry(tree, &entry)) {
		int te_len = tree_entry_len(&entry);

		if (match != all_entries_interesting) {
			strbuf_addstr(&name, base->buf + tn_len);
			match = tree_entry_interesting(repo->index,
						       &entry, &name,
						       0, pathspec);
			strbuf_setlen(&name, name_base_len);

			if (match == all_entries_not_interesting)
				break;
			if (match == entry_not_interesting)
				continue;
		}

		strbuf_add(base, entry.path, te_len);

		if (S_ISREG(entry.mode)) {
			hit |= grep_oid(opt, &entry.oid, base->buf, tn_len,
					 check_attr ? base->buf + tn_len : NULL);
		} else if (S_ISDIR(entry.mode)) {
			enum object_type type;
			struct tree_desc sub;
			void *data;
			unsigned long size;

			data = read_object_file(&entry.oid, &type, &size);
			if (!data)
				die(_("unable to read tree (%s)"),
				    oid_to_hex(&entry.oid));

			strbuf_addch(base, '/');
			init_tree_desc(&sub, data, size);
			hit |= grep_tree(opt, pathspec, &sub, base, tn_len,
					 check_attr);
			free(data);
		} else if (recurse_submodules && S_ISGITLINK(entry.mode)) {
			hit |= grep_submodule(opt, pathspec, &entry.oid,
					      base->buf, base->buf + tn_len,
					      1); /* ignored */
		}

		strbuf_setlen(base, old_baselen);

		if (hit && opt->status_only)
			break;
	}

	strbuf_release(&name);
	return hit;
}

static int grep_object(struct grep_opt *opt, const struct pathspec *pathspec,
		       struct object *obj, const char *name, const char *path)
{
	if (obj->type == OBJ_BLOB)
		return grep_oid(opt, &obj->oid, name, 0, path);
	if (obj->type == OBJ_COMMIT || obj->type == OBJ_TREE) {
		struct tree_desc tree;
		void *data;
		unsigned long size;
		struct strbuf base;
		int hit, len;

		data = read_object_with_reference(opt->repo,
						  &obj->oid, OBJ_TREE,
						  &size, NULL);
		if (!data)
			die(_("unable to read tree (%s)"), oid_to_hex(&obj->oid));

		len = name ? strlen(name) : 0;
		strbuf_init(&base, PATH_MAX + len + 1);
		if (len) {
			strbuf_add(&base, name, len);
			strbuf_addch(&base, ':');
		}
		init_tree_desc(&tree, data, size);
		hit = grep_tree(opt, pathspec, &tree, &base, base.len,
				obj->type == OBJ_COMMIT);
		strbuf_release(&base);
		free(data);
		return hit;
	}
	die(_("unable to grep from object of type %s"), type_name(obj->type));
}

static int grep_objects(struct grep_opt *opt, const struct pathspec *pathspec,
			const struct object_array *list)
{
	unsigned int i;
	int hit = 0;
	const unsigned int nr = list->nr;

	for (i = 0; i < nr; i++) {
		struct object *real_obj;

		obj_read_lock();
		real_obj = deref_tag(opt->repo, list->objects[i].item,
				     NULL, 0);
		obj_read_unlock();

		if (!real_obj) {
			char hex[GIT_MAX_HEXSZ + 1];
			const char *name = list->objects[i].name;

			if (!name) {
				oid_to_hex_r(hex, &list->objects[i].item->oid);
				name = hex;
			}
			die(_("invalid object '%s' given."), name);
		}

		/* load the gitmodules file for this rev */
		if (recurse_submodules) {
			submodule_free(opt->repo);
			obj_read_lock();
			gitmodules_config_oid(&real_obj->oid);
			obj_read_unlock();
		}
		if (grep_object(opt, pathspec, real_obj, list->objects[i].name,
				list->objects[i].path)) {
			hit = 1;
			if (opt->status_only)
				break;
		}
	}
	return hit;
}

static int grep_directory(struct grep_opt *opt, const struct pathspec *pathspec,
			  int exc_std, int use_index)
{
	struct dir_struct dir = DIR_INIT;
	int i, hit = 0;

	if (!use_index)
		dir.flags |= DIR_NO_GITLINKS;
	if (exc_std)
		setup_standard_excludes(&dir);

	fill_directory(&dir, opt->repo->index, pathspec);
	for (i = 0; i < dir.nr; i++) {
		hit |= grep_file(opt, dir.entries[i]->name);
		if (hit && opt->status_only)
			break;
	}
	dir_clear(&dir);
	return hit;
}

static int context_callback(const struct option *opt, const char *arg,
			    int unset)
{
	struct grep_opt *grep_opt = opt->value;
	int value;
	const char *endp;

	if (unset) {
		grep_opt->pre_context = grep_opt->post_context = 0;
		return 0;
	}
	value = strtol(arg, (char **)&endp, 10);
	if (*endp) {
		return error(_("switch `%c' expects a numerical value"),
			     opt->short_name);
	}
	grep_opt->pre_context = grep_opt->post_context = value;
	return 0;
}

static int file_callback(const struct option *opt, const char *arg, int unset)
{
	struct grep_opt *grep_opt = opt->value;
	int from_stdin;
	FILE *patterns;
	int lno = 0;
	struct strbuf sb = STRBUF_INIT;

	BUG_ON_OPT_NEG(unset);

	from_stdin = !strcmp(arg, "-");
	patterns = from_stdin ? stdin : fopen(arg, "r");
	if (!patterns)
		die_errno(_("cannot open '%s'"), arg);
	while (strbuf_getline(&sb, patterns) == 0) {
		/* ignore empty line like grep does */
		if (sb.len == 0)
			continue;

		append_grep_pat(grep_opt, sb.buf, sb.len, arg, ++lno,
				GREP_PATTERN);
	}
	if (!from_stdin)
		fclose(patterns);
	strbuf_release(&sb);
	return 0;
}

static int not_callback(const struct option *opt, const char *arg, int unset)
{
	struct grep_opt *grep_opt = opt->value;
	BUG_ON_OPT_NEG(unset);
	BUG_ON_OPT_ARG(arg);
	append_grep_pattern(grep_opt, "--not", "command line", 0, GREP_NOT);
	return 0;
}

static int and_callback(const struct option *opt, const char *arg, int unset)
{
	struct grep_opt *grep_opt = opt->value;
	BUG_ON_OPT_NEG(unset);
	BUG_ON_OPT_ARG(arg);
	append_grep_pattern(grep_opt, "--and", "command line", 0, GREP_AND);
	return 0;
}

static int open_callback(const struct option *opt, const char *arg, int unset)
{
	struct grep_opt *grep_opt = opt->value;
	BUG_ON_OPT_NEG(unset);
	BUG_ON_OPT_ARG(arg);
	append_grep_pattern(grep_opt, "(", "command line", 0, GREP_OPEN_PAREN);
	return 0;
}

static int close_callback(const struct option *opt, const char *arg, int unset)
{
	struct grep_opt *grep_opt = opt->value;
	BUG_ON_OPT_NEG(unset);
	BUG_ON_OPT_ARG(arg);
	append_grep_pattern(grep_opt, ")", "command line", 0, GREP_CLOSE_PAREN);
	return 0;
}

static int pattern_callback(const struct option *opt, const char *arg,
			    int unset)
{
	struct grep_opt *grep_opt = opt->value;
	BUG_ON_OPT_NEG(unset);
	append_grep_pattern(grep_opt, arg, "-e option", 0, GREP_PATTERN);
	return 0;
}

int cmd_grep(int argc, const char **argv, const char *prefix)
{
	int hit = 0;
	int cached = 0, untracked = 0, opt_exclude = -1;
	int seen_dashdash = 0;
	int external_grep_allowed__ignored;
	const char *show_in_pager = NULL, *default_pager = "dummy";
	struct grep_opt opt;
	struct object_array list = OBJECT_ARRAY_INIT;
	struct pathspec pathspec;
	struct string_list path_list = STRING_LIST_INIT_DUP;
	int i;
	int dummy;
	int use_index = 1;
	int allow_revs;

	struct option options[] = {
		OPT_BOOL(0, "cached", &cached,
			N_("search in index instead of in the work tree")),
		OPT_NEGBIT(0, "no-index", &use_index,
			 N_("find in contents not managed by git"), 1),
		OPT_BOOL(0, "untracked", &untracked,
			N_("search in both tracked and untracked files")),
		OPT_SET_INT(0, "exclude-standard", &opt_exclude,
			    N_("ignore files specified via '.gitignore'"), 1),
		OPT_BOOL(0, "recurse-submodules", &recurse_submodules,
			 N_("recursively search in each submodule")),
		OPT_GROUP(""),
		OPT_BOOL('v', "invert-match", &opt.invert,
			N_("show non-matching lines")),
		OPT_BOOL('i', "ignore-case", &opt.ignore_case,
			N_("case insensitive matching")),
		OPT_BOOL('w', "word-regexp", &opt.word_regexp,
			N_("match patterns only at word boundaries")),
		OPT_SET_INT('a', "text", &opt.binary,
			N_("process binary files as text"), GREP_BINARY_TEXT),
		OPT_SET_INT('I', NULL, &opt.binary,
			N_("don't match patterns in binary files"),
			GREP_BINARY_NOMATCH),
		OPT_BOOL(0, "textconv", &opt.allow_textconv,
			 N_("process binary files with textconv filters")),
		OPT_SET_INT('r', "recursive", &opt.max_depth,
			    N_("search in subdirectories (default)"), -1),
		{ OPTION_INTEGER, 0, "max-depth", &opt.max_depth, N_("depth"),
			N_("descend at most <depth> levels"), PARSE_OPT_NONEG,
			NULL, 1 },
		OPT_GROUP(""),
		OPT_SET_INT('E', "extended-regexp", &opt.pattern_type_option,
			    N_("use extended POSIX regular expressions"),
			    GREP_PATTERN_TYPE_ERE),
		OPT_SET_INT('G', "basic-regexp", &opt.pattern_type_option,
			    N_("use basic POSIX regular expressions (default)"),
			    GREP_PATTERN_TYPE_BRE),
		OPT_SET_INT('F', "fixed-strings", &opt.pattern_type_option,
			    N_("interpret patterns as fixed strings"),
			    GREP_PATTERN_TYPE_FIXED),
		OPT_SET_INT('P', "perl-regexp", &opt.pattern_type_option,
			    N_("use Perl-compatible regular expressions"),
			    GREP_PATTERN_TYPE_PCRE),
		OPT_GROUP(""),
		OPT_BOOL('n', "line-number", &opt.linenum, N_("show line numbers")),
		OPT_BOOL(0, "column", &opt.columnnum, N_("show column number of first match")),
		OPT_NEGBIT('h', NULL, &opt.pathname, N_("don't show filenames"), 1),
		OPT_BIT('H', NULL, &opt.pathname, N_("show filenames"), 1),
		OPT_NEGBIT(0, "full-name", &opt.relative,
			N_("show filenames relative to top directory"), 1),
		OPT_BOOL('l', "files-with-matches", &opt.name_only,
			N_("show only filenames instead of matching lines")),
		OPT_BOOL(0, "name-only", &opt.name_only,
			N_("synonym for --files-with-matches")),
		OPT_BOOL('L', "files-without-match",
			&opt.unmatch_name_only,
			N_("show only the names of files without match")),
		OPT_BOOL_F('z', "null", &opt.null_following_name,
			   N_("print NUL after filenames"),
			   PARSE_OPT_NOCOMPLETE),
		OPT_BOOL('o', "only-matching", &opt.only_matching,
			N_("show only matching parts of a line")),
		OPT_BOOL('c', "count", &opt.count,
			N_("show the number of matches instead of matching lines")),
		OPT__COLOR(&opt.color, N_("highlight matches")),
		OPT_BOOL(0, "break", &opt.file_break,
			N_("print empty line between matches from different files")),
		OPT_BOOL(0, "heading", &opt.heading,
			N_("show filename only once above matches from same file")),
		OPT_GROUP(""),
		OPT_CALLBACK('C', "context", &opt, N_("n"),
			N_("show <n> context lines before and after matches"),
			context_callback),
		OPT_INTEGER('B', "before-context", &opt.pre_context,
			N_("show <n> context lines before matches")),
		OPT_INTEGER('A', "after-context", &opt.post_context,
			N_("show <n> context lines after matches")),
		OPT_INTEGER(0, "threads", &num_threads,
			N_("use <n> worker threads")),
		OPT_NUMBER_CALLBACK(&opt, N_("shortcut for -C NUM"),
			context_callback),
		OPT_BOOL('p', "show-function", &opt.funcname,
			N_("show a line with the function name before matches")),
		OPT_BOOL('W', "function-context", &opt.funcbody,
			N_("show the surrounding function")),
		OPT_GROUP(""),
		OPT_CALLBACK('f', NULL, &opt, N_("file"),
			N_("read patterns from file"), file_callback),
		OPT_CALLBACK_F('e', NULL, &opt, N_("pattern"),
			N_("match <pattern>"), PARSE_OPT_NONEG, pattern_callback),
		OPT_CALLBACK_F(0, "and", &opt, NULL,
			N_("combine patterns specified with -e"),
			PARSE_OPT_NOARG | PARSE_OPT_NONEG, and_callback),
		OPT_BOOL(0, "or", &dummy, ""),
		OPT_CALLBACK_F(0, "not", &opt, NULL, "",
			PARSE_OPT_NOARG | PARSE_OPT_NONEG, not_callback),
		OPT_CALLBACK_F('(', NULL, &opt, NULL, "",
			PARSE_OPT_NOARG | PARSE_OPT_NONEG | PARSE_OPT_NODASH,
			open_callback),
		OPT_CALLBACK_F(')', NULL, &opt, NULL, "",
			PARSE_OPT_NOARG | PARSE_OPT_NONEG | PARSE_OPT_NODASH,
			close_callback),
		OPT__QUIET(&opt.status_only,
			   N_("indicate hit with exit status without output")),
		OPT_BOOL(0, "all-match", &opt.all_match,
			N_("show only matches from files that match all patterns")),
		OPT_GROUP(""),
		{ OPTION_STRING, 'O', "open-files-in-pager", &show_in_pager,
			N_("pager"), N_("show matching files in the pager"),
			PARSE_OPT_OPTARG | PARSE_OPT_NOCOMPLETE,
			NULL, (intptr_t)default_pager },
		OPT_BOOL_F(0, "ext-grep", &external_grep_allowed__ignored,
			   N_("allow calling of grep(1) (ignored by this build)"),
			   PARSE_OPT_NOCOMPLETE),
		OPT_INTEGER('m', "max-count", &opt.max_count,
			N_("maximum number of results per file")),
		OPT_END()
	};
	grep_prefix = prefix;

	grep_init(&opt, the_repository);
	git_config(grep_cmd_config, &opt);

	/*
	 * If there is no -- then the paths must exist in the working
	 * tree.  If there is no explicit pattern specified with -e or
	 * -f, we take the first unrecognized non option to be the
	 * pattern, but then what follows it must be zero or more
	 * valid refs up to the -- (if exists), and then existing
	 * paths.  If there is an explicit pattern, then the first
	 * unrecognized non option is the beginning of the refs list
	 * that continues up to the -- (if exists), and then paths.
	 */
	argc = parse_options(argc, argv, prefix, options, grep_usage,
			     PARSE_OPT_KEEP_DASHDASH |
			     PARSE_OPT_STOP_AT_NON_OPTION);

	if (the_repository->gitdir) {
		prepare_repo_settings(the_repository);
		the_repository->settings.command_requires_full_index = 0;
	}

	if (use_index && !startup_info->have_repository) {
		int fallback = 0;
		git_config_get_bool("grep.fallbacktonoindex", &fallback);
		if (fallback)
			use_index = 0;
		else
			/* die the same way as if we did it at the beginning */
			setup_git_directory();
	}
	/* Ignore --recurse-submodules if --no-index is given or implied */
	if (!use_index)
		recurse_submodules = 0;

	/*
	 * skip a -- separator; we know it cannot be
	 * separating revisions from pathnames if
	 * we haven't even had any patterns yet
	 */
	if (argc > 0 && !opt.pattern_list && !strcmp(argv[0], "--")) {
		argv++;
		argc--;
	}

	/* First unrecognized non-option token */
	if (argc > 0 && !opt.pattern_list) {
		append_grep_pattern(&opt, argv[0], "command line", 0,
				    GREP_PATTERN);
		argv++;
		argc--;
	}

	if (show_in_pager == default_pager)
		show_in_pager = git_pager(1);
	if (show_in_pager) {
		opt.color = 0;
		opt.name_only = 1;
		opt.null_following_name = 1;
		opt.output_priv = &path_list;
		opt.output = append_path;
		string_list_append(&path_list, show_in_pager);
	}

	if (!opt.pattern_list)
		die(_("no pattern given"));

	/* --only-matching has no effect with --invert. */
	if (opt.invert)
		opt.only_matching = 0;

	/*
	 * We have to find "--" in a separate pass, because its presence
	 * influences how we will parse arguments that come before it.
	 */
	for (i = 0; i < argc; i++) {
		if (!strcmp(argv[i], "--")) {
			seen_dashdash = 1;
			break;
		}
	}

	/*
	 * Resolve any rev arguments. If we have a dashdash, then everything up
	 * to it must resolve as a rev. If not, then we stop at the first
	 * non-rev and assume everything else is a path.
	 */
	allow_revs = use_index && !untracked;
	for (i = 0; i < argc; i++) {
		const char *arg = argv[i];
		struct object_id oid;
		struct object_context oc;
		struct object *object;

		if (!strcmp(arg, "--")) {
			i++;
			break;
		}

		if (!allow_revs) {
			if (seen_dashdash)
				die(_("--no-index or --untracked cannot be used with revs"));
			break;
		}

		if (get_oid_with_context(the_repository, arg,
					 GET_OID_RECORD_PATH,
					 &oid, &oc)) {
			if (seen_dashdash)
				die(_("unable to resolve revision: %s"), arg);
			break;
		}

		object = parse_object_or_die(&oid, arg);
		if (!seen_dashdash)
			verify_non_filename(prefix, arg);
		add_object_array_with_path(object, arg, &list, oc.mode, oc.path);
		free(oc.path);
	}

	/*
	 * Anything left over is presumed to be a path. But in the non-dashdash
	 * "do what I mean" case, we verify and complain when that isn't true.
	 */
	if (!seen_dashdash) {
		int j;
		for (j = i; j < argc; j++)
			verify_filename(prefix, argv[j], j == i && allow_revs);
	}

	parse_pathspec(&pathspec, 0,
		       PATHSPEC_PREFER_CWD |
		       (opt.max_depth != -1 ? PATHSPEC_MAXDEPTH_VALID : 0),
		       prefix, argv + i);
	pathspec.max_depth = opt.max_depth;
	pathspec.recursive = 1;
	pathspec.recurse_submodules = !!recurse_submodules;

	if (recurse_submodules && untracked)
		die(_("--untracked not supported with --recurse-submodules"));

	/*
	 * Optimize out the case where the amount of matches is limited to zero.
	 * We do this to keep results consistent with GNU grep(1).
	 */
	if (opt.max_count == 0)
		return 1;

	if (show_in_pager) {
		if (num_threads > 1)
			warning(_("invalid option combination, ignoring --threads"));
		num_threads = 1;
	} else if (!HAVE_THREADS && num_threads > 1) {
		warning(_("no threads support, ignoring --threads"));
		num_threads = 1;
	} else if (num_threads < 0)
		die(_("invalid number of threads specified (%d)"), num_threads);
	else if (num_threads == 0)
		num_threads = HAVE_THREADS ? online_cpus() : 1;

	if (num_threads > 1) {
		if (!HAVE_THREADS)
			BUG("Somebody got num_threads calculation wrong!");
		if (!(opt.name_only || opt.unmatch_name_only || opt.count)
		    && (opt.pre_context || opt.post_context ||
			opt.file_break || opt.funcbody))
			skip_first_line = 1;

		/*
		 * Pre-read gitmodules (if not read already) and force eager
		 * initialization of packed_git to prevent racy lazy
		 * reading/initialization once worker threads are started.
		 */
		if (recurse_submodules)
			repo_read_gitmodules(the_repository, 1);
		if (startup_info->have_repository)
			(void)get_packed_git(the_repository);

		start_threads(&opt);
	} else {
		/*
		 * The compiled patterns on the main path are only
		 * used when not using threading. Otherwise
		 * start_threads() above calls compile_grep_patterns()
		 * for each thread.
		 */
		compile_grep_patterns(&opt);
	}

	if (show_in_pager && (cached || list.nr))
		die(_("--open-files-in-pager only works on the worktree"));

	if (show_in_pager && opt.pattern_list && !opt.pattern_list->next) {
		const char *pager = path_list.items[0].string;
		int len = strlen(pager);

		if (len > 4 && is_dir_sep(pager[len - 5]))
			pager += len - 4;

		if (opt.ignore_case && !strcmp("less", pager))
			string_list_append(&path_list, "-I");

		if (!strcmp("less", pager) || !strcmp("vi", pager)) {
			struct strbuf buf = STRBUF_INIT;
			strbuf_addf(&buf, "+/%s%s",
					strcmp("less", pager) ? "" : "*",
					opt.pattern_list->pattern);
			string_list_append_nodup(&path_list,
						 strbuf_detach(&buf, NULL));
		}
	}

	if (!show_in_pager && !opt.status_only)
		setup_pager();

	die_for_incompatible_opt3(!use_index, "--no-index",
				  untracked, "--untracked",
				  cached, "--cached");

	if (!use_index || untracked) {
		int use_exclude = (opt_exclude < 0) ? use_index : !!opt_exclude;
		hit = grep_directory(&opt, &pathspec, use_exclude, use_index);
	} else if (0 <= opt_exclude) {
		die(_("--[no-]exclude-standard cannot be used for tracked contents"));
	} else if (!list.nr) {
		if (!cached)
			setup_work_tree();

		hit = grep_cache(&opt, &pathspec, cached);
	} else {
		if (cached)
			die(_("both --cached and trees are given"));

		hit = grep_objects(&opt, &pathspec, &list);
	}

	if (num_threads > 1)
		hit |= wait_all();
	if (hit && show_in_pager)
		run_pager(&opt, prefix);
	clear_pathspec(&pathspec);
	string_list_clear(&path_list, 0);
	free_grep_patterns(&opt);
	object_array_clear(&list);
	free_repos();
	return !hit;
}