/*
 * Builtin "git grep"
 *
 * Copyright (c) 2006 Junio C Hamano
 */
#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"

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

static int recurse_submodules;

#define GREP_NUM_THREADS_DEFAULT 8
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;

/* 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, const struct grep_source *gs)
{
        grep_lock();

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

        todo[todo_end].source = *gs;
        if (opt->binary != GREP_BINARY_TEXT)
                grep_source_load_driver(&todo[todo_end].source,
                                        opt->repo->index);
        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 *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(arg);
        free(arg);

        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_read_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;

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

        threads = xcalloc(num_threads, sizeof(*threads));
        for (i = 0; i < num_threads; i++) {
                int err;
                struct grep_opt *o = grep_opt_dup(opt);
                o->output = strbuf_out;
                if (i)
                        o->debug = 0;
                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_read_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;

        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, cb) < 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 *lock_and_read_oid_file(const struct object_id *oid, enum object_type *type, unsigned long *size)
{
        void *data;

        grep_read_lock();
        data = read_object_file(oid, type, size);
        grep_read_unlock();
        return data;
}

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;

        if (opt->relative && opt->prefix_length) {
                quote_path_relative(filename + tree_name_len, opt->prefix, &pathbuf);
                strbuf_insert(&pathbuf, 0, filename, tree_name_len);
        } else {
                strbuf_addstr(&pathbuf, filename);
        }

        grep_source_init(&gs, GREP_SOURCE_OID, pathbuf.buf, path, oid);
        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;

        if (opt->relative && opt->prefix_length)
                quote_path_relative(filename, opt->prefix, &buf);
        else
                strbuf_addstr(&buf, filename);

        grep_source_init(&gs, GREP_SOURCE_FILE, buf.buf, filename, 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(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++)
                argv_array_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, struct repository *repo,
                      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, struct repository *repo);

static int grep_submodule(struct grep_opt *opt, struct repository *superproject,
                          const struct pathspec *pathspec,
                          const struct object_id *oid,
                          const char *filename, const char *path)
{
        struct repository subrepo;
        const struct submodule *sub = submodule_from_path(superproject,
                                                          &null_oid, path);

        int hit;

        /*
         * NEEDSWORK: submodules functions need to be protected because they
         * access the object store via config_from_gitmodules(): the latter
         * uses get_oid() which, for now, relies on the global the_repository
         * object.
         */
        grep_read_lock();

        if (!is_submodule_active(superproject, path)) {
                grep_read_unlock();
                return 0;
        }

        if (repo_submodule_init(&subrepo, superproject, sub)) {
                grep_read_unlock();
                return 0;
        }

        repo_read_gitmodules(&subrepo);

        /*
         * NEEDSWORK: This adds the submodule's object directory to the list of
         * alternates for the single in-memory object store.  This has some bad
         * consequences for memory (processed objects will never be freed) and
         * performance (this increases the number of pack files git has to pay
         * attention to, to the sum of the number of pack files in all the
         * repositories processed so far).  This can be removed once the object
         * store is no longer global and instead is a member of the repository
         * object.
         */
        add_to_alternates_memory(subrepo.objects->objectdir);
        grep_read_unlock();

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

                object = parse_object_or_die(oid, oid_to_hex(oid));

                grep_read_lock();
                data = read_object_with_reference(&object->oid, tree_type,
                                                  &size, NULL);
                grep_read_unlock();

                if (!data)
                        die(_("unable to read tree (%s)"), oid_to_hex(&object->oid));

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

                init_tree_desc(&tree, data, size);
                hit = grep_tree(opt, pathspec, &tree, &base, base.len,
                                object->type == OBJ_COMMIT, &subrepo);
                strbuf_release(&base);
                free(data);
        } else {
                hit = grep_cache(opt, &subrepo, pathspec, 1);
        }

        repo_clear(&subrepo);
        return hit;
}

static int grep_cache(struct grep_opt *opt, struct repository *repo,
                      const struct pathspec *pathspec, int cached)
{
        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];
                strbuf_setlen(&name, name_base_len);
                strbuf_addstr(&name, ce->name);

                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) ||
                            ce_skip_worktree(ce)) {
                                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, repo, pathspec, NULL, ce->name, ce->name);
                } 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)
{
        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(&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 = lock_and_read_oid_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, repo);
                        free(data);
                } else if (recurse_submodules && S_ISGITLINK(entry.mode)) {
                        hit |= grep_submodule(opt, repo, pathspec, entry.oid,
                                              base->buf, base->buf + tn_len);
                }

                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;

                grep_read_lock();
                data = read_object_with_reference(&obj->oid, tree_type,
                                                  &size, NULL);
                grep_read_unlock();

                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, the_repository);
                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;
                real_obj = deref_tag(the_repository, list->objects[i].item,
                                     NULL, 0);

                /* load the gitmodules file for this rev */
                if (recurse_submodules) {
                        submodule_free(the_repository);
                        gitmodules_config_oid(&real_obj->oid);
                }
                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;
        int i, hit = 0;

        memset(&dir, 0, sizeof(dir));
        if (!use_index)
                dir.flags |= DIR_NO_GITLINKS;
        if (exc_std)
                setup_standard_excludes(&dir);

        fill_directory(&dir, &the_index, pathspec);
        for (i = 0; i < dir.nr; i++) {
                if (!dir_path_match(&the_index, dir.entries[i], pathspec, 0, NULL))
                        continue;
                hit |= grep_file(opt, dir.entries[i]->name);
                if (hit && opt->status_only)
                        break;
        }
        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_NODUP;
        int i;
        int dummy;
        int use_index = 1;
        int pattern_type_arg = GREP_PATTERN_TYPE_UNSPECIFIED;
        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", &pattern_type_arg,
                            N_("use extended POSIX regular expressions"),
                            GREP_PATTERN_TYPE_ERE),
                OPT_SET_INT('G', "basic-regexp", &pattern_type_arg,
                            N_("use basic POSIX regular expressions (default)"),
                            GREP_PATTERN_TYPE_BRE),
                OPT_SET_INT('F', "fixed-strings", &pattern_type_arg,
                            N_("interpret patterns as fixed strings"),
                            GREP_PATTERN_TYPE_FIXED),
                OPT_SET_INT('P', "perl-regexp", &pattern_type_arg,
                            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),
                { OPTION_CALLBACK, 'e', NULL, &opt, N_("pattern"),
                        N_("match <pattern>"), PARSE_OPT_NONEG, pattern_callback },
                { OPTION_CALLBACK, 0, "and", &opt, NULL,
                  N_("combine patterns specified with -e"),
                  PARSE_OPT_NOARG | PARSE_OPT_NONEG, and_callback },
                OPT_BOOL(0, "or", &dummy, ""),
                { OPTION_CALLBACK, 0, "not", &opt, NULL, "",
                  PARSE_OPT_NOARG | PARSE_OPT_NONEG, not_callback },
                { OPTION_CALLBACK, '(', NULL, &opt, NULL, "",
                  PARSE_OPT_NOARG | PARSE_OPT_NONEG | PARSE_OPT_NODASH,
                  open_callback },
                { OPTION_CALLBACK, ')', 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_SET_INT_F(0, "debug", &opt.debug,
                              N_("show parse tree for grep expression"),
                              1, PARSE_OPT_HIDDEN),
                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_END()
        };

        init_grep_defaults(the_repository);
        git_config(grep_cmd_config, NULL);
        grep_init(&opt, the_repository, prefix);

        /*
         * 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);
        grep_commit_pattern_type(pattern_type_arg, &opt);

        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();
        }

        /*
         * 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(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 (list.nr || cached || 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 ? GREP_NUM_THREADS_DEFAULT : 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;
                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(&path_list, buf.buf);
                        strbuf_detach(&buf, NULL);
                }
        }

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

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

        if (!use_index && (untracked || cached))
                die(_("--cached or --untracked cannot be used with --no-index"));

        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, the_repository, &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);
        free_grep_patterns(&opt);
        return !hit;
}