#include "cache.h"
#include "tag.h"
#include "blob.h"
#include "tree.h"
#include "commit.h"
#include "diff.h"
#include "refs.h"
#include "revision.h"
#include "grep.h"

static char *path_name(struct name_path *path, const char *name)
{
	struct name_path *p;
	char *n, *m;
	int nlen = strlen(name);
	int len = nlen + 1;

	for (p = path; p; p = p->up) {
		if (p->elem_len)
			len += p->elem_len + 1;
	}
	n = xmalloc(len);
	m = n + len - (nlen + 1);
	strcpy(m, name);
	for (p = path; p; p = p->up) {
		if (p->elem_len) {
			m -= p->elem_len + 1;
			memcpy(m, p->elem, p->elem_len);
			m[p->elem_len] = '/';
		}
	}
	return n;
}

void add_object(struct object *obj,
		struct object_array *p,
		struct name_path *path,
		const char *name)
{
	add_object_array(obj, path_name(path, name), p);
}

static void mark_blob_uninteresting(struct blob *blob)
{
	if (blob->object.flags & UNINTERESTING)
		return;
	blob->object.flags |= UNINTERESTING;
}

void mark_tree_uninteresting(struct tree *tree)
{
	struct tree_desc desc;
	struct name_entry entry;
	struct object *obj = &tree->object;

	if (obj->flags & UNINTERESTING)
		return;
	obj->flags |= UNINTERESTING;
	if (!has_sha1_file(obj->sha1))
		return;
	if (parse_tree(tree) < 0)
		die("bad tree %s", sha1_to_hex(obj->sha1));

	desc.buf = tree->buffer;
	desc.size = tree->size;
	while (tree_entry(&desc, &entry)) {
		if (S_ISDIR(entry.mode))
			mark_tree_uninteresting(lookup_tree(entry.sha1));
		else
			mark_blob_uninteresting(lookup_blob(entry.sha1));
	}

	/*
	 * We don't care about the tree any more
	 * after it has been marked uninteresting.
	 */
	free(tree->buffer);
	tree->buffer = NULL;
}

void mark_parents_uninteresting(struct commit *commit)
{
	struct commit_list *parents = commit->parents;

	while (parents) {
		struct commit *commit = parents->item;
		if (!(commit->object.flags & UNINTERESTING)) {
			commit->object.flags |= UNINTERESTING;

			/*
			 * Normally we haven't parsed the parent
			 * yet, so we won't have a parent of a parent
			 * here. However, it may turn out that we've
			 * reached this commit some other way (where it
			 * wasn't uninteresting), in which case we need
			 * to mark its parents recursively too..
			 */
			if (commit->parents)
				mark_parents_uninteresting(commit);
		}

		/*
		 * A missing commit is ok iff its parent is marked
		 * uninteresting.
		 *
		 * We just mark such a thing parsed, so that when
		 * it is popped next time around, we won't be trying
		 * to parse it and get an error.
		 */
		if (!has_sha1_file(commit->object.sha1))
			commit->object.parsed = 1;
		parents = parents->next;
	}
}

void add_pending_object(struct rev_info *revs, struct object *obj, const char *name)
{
	add_object_array(obj, name, &revs->pending);
}

static struct object *get_reference(struct rev_info *revs, const char *name, const unsigned char *sha1, unsigned int flags)
{
	struct object *object;

	object = parse_object(sha1);
	if (!object)
		die("bad object %s", name);
	object->flags |= flags;
	return object;
}

static struct commit *handle_commit(struct rev_info *revs, struct object *object, const char *name)
{
	unsigned long flags = object->flags;

	/*
	 * Tag object? Look what it points to..
	 */
	while (object->type == OBJ_TAG) {
		struct tag *tag = (struct tag *) object;
		if (revs->tag_objects && !(flags & UNINTERESTING))
			add_pending_object(revs, object, tag->tag);
		object = parse_object(tag->tagged->sha1);
		if (!object)
			die("bad object %s", sha1_to_hex(tag->tagged->sha1));
	}

	/*
	 * Commit object? Just return it, we'll do all the complex
	 * reachability crud.
	 */
	if (object->type == OBJ_COMMIT) {
		struct commit *commit = (struct commit *)object;
		if (parse_commit(commit) < 0)
			die("unable to parse commit %s", name);
		if (flags & UNINTERESTING) {
			commit->object.flags |= UNINTERESTING;
			mark_parents_uninteresting(commit);
			revs->limited = 1;
		}
		return commit;
	}

	/*
	 * Tree object? Either mark it uniniteresting, or add it
	 * to the list of objects to look at later..
	 */
	if (object->type == OBJ_TREE) {
		struct tree *tree = (struct tree *)object;
		if (!revs->tree_objects)
			return NULL;
		if (flags & UNINTERESTING) {
			mark_tree_uninteresting(tree);
			return NULL;
		}
		add_pending_object(revs, object, "");
		return NULL;
	}

	/*
	 * Blob object? You know the drill by now..
	 */
	if (object->type == OBJ_BLOB) {
		struct blob *blob = (struct blob *)object;
		if (!revs->blob_objects)
			return NULL;
		if (flags & UNINTERESTING) {
			mark_blob_uninteresting(blob);
			return NULL;
		}
		add_pending_object(revs, object, "");
		return NULL;
	}
	die("%s is unknown object", name);
}

static int everybody_uninteresting(struct commit_list *orig)
{
	struct commit_list *list = orig;
	while (list) {
		struct commit *commit = list->item;
		list = list->next;
		if (commit->object.flags & UNINTERESTING)
			continue;
		return 0;
	}
	return 1;
}

static int tree_difference = REV_TREE_SAME;

static void file_add_remove(struct diff_options *options,
		    int addremove, unsigned mode,
		    const unsigned char *sha1,
		    const char *base, const char *path)
{
	int diff = REV_TREE_DIFFERENT;

	/*
	 * Is it an add of a new file? It means that the old tree
	 * didn't have it at all, so we will turn "REV_TREE_SAME" ->
	 * "REV_TREE_NEW", but leave any "REV_TREE_DIFFERENT" alone
	 * (and if it already was "REV_TREE_NEW", we'll keep it
	 * "REV_TREE_NEW" of course).
	 */
	if (addremove == '+') {
		diff = tree_difference;
		if (diff != REV_TREE_SAME)
			return;
		diff = REV_TREE_NEW;
	}
	tree_difference = diff;
}

static void file_change(struct diff_options *options,
		 unsigned old_mode, unsigned new_mode,
		 const unsigned char *old_sha1,
		 const unsigned char *new_sha1,
		 const char *base, const char *path)
{
	tree_difference = REV_TREE_DIFFERENT;
}

int rev_compare_tree(struct rev_info *revs, struct tree *t1, struct tree *t2)
{
	if (!t1)
		return REV_TREE_NEW;
	if (!t2)
		return REV_TREE_DIFFERENT;
	tree_difference = REV_TREE_SAME;
	if (diff_tree_sha1(t1->object.sha1, t2->object.sha1, "",
			   &revs->pruning) < 0)
		return REV_TREE_DIFFERENT;
	return tree_difference;
}

int rev_same_tree_as_empty(struct rev_info *revs, struct tree *t1)
{
	int retval;
	void *tree;
	struct tree_desc empty, real;

	if (!t1)
		return 0;

	tree = read_object_with_reference(t1->object.sha1, tree_type, &real.size, NULL);
	if (!tree)
		return 0;
	real.buf = tree;

	empty.buf = "";
	empty.size = 0;

	tree_difference = 0;
	retval = diff_tree(&empty, &real, "", &revs->pruning);
	free(tree);

	return retval >= 0 && !tree_difference;
}

static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
{
	struct commit_list **pp, *parent;
	int tree_changed = 0, tree_same = 0;

	if (!commit->tree)
		return;

	if (!commit->parents) {
		if (!rev_same_tree_as_empty(revs, commit->tree))
			commit->object.flags |= TREECHANGE;
		return;
	}

	pp = &commit->parents;
	while ((parent = *pp) != NULL) {
		struct commit *p = parent->item;

		parse_commit(p);
		switch (rev_compare_tree(revs, p->tree, commit->tree)) {
		case REV_TREE_SAME:
			tree_same = 1;
			if (!revs->simplify_history || (p->object.flags & UNINTERESTING)) {
				/* Even if a merge with an uninteresting
				 * side branch brought the entire change
				 * we are interested in, we do not want
				 * to lose the other branches of this
				 * merge, so we just keep going.
				 */
				pp = &parent->next;
				continue;
			}
			parent->next = NULL;
			commit->parents = parent;
			return;

		case REV_TREE_NEW:
			if (revs->remove_empty_trees &&
			    rev_same_tree_as_empty(revs, p->tree)) {
				/* We are adding all the specified
				 * paths from this parent, so the
				 * history beyond this parent is not
				 * interesting.  Remove its parents
				 * (they are grandparents for us).
				 * IOW, we pretend this parent is a
				 * "root" commit.
				 */
				parse_commit(p);
				p->parents = NULL;
			}
		/* fallthrough */
		case REV_TREE_DIFFERENT:
			tree_changed = 1;
			pp = &parent->next;
			continue;
		}
		die("bad tree compare for commit %s", sha1_to_hex(commit->object.sha1));
	}
	if (tree_changed && !tree_same)
		commit->object.flags |= TREECHANGE;
}

static void add_parents_to_list(struct rev_info *revs, struct commit *commit, struct commit_list **list)
{
	struct commit_list *parent = commit->parents;
	unsigned left_flag;

	if (commit->object.flags & ADDED)
		return;
	commit->object.flags |= ADDED;

	/*
	 * If the commit is uninteresting, don't try to
	 * prune parents - we want the maximal uninteresting
	 * set.
	 *
	 * Normally we haven't parsed the parent
	 * yet, so we won't have a parent of a parent
	 * here. However, it may turn out that we've
	 * reached this commit some other way (where it
	 * wasn't uninteresting), in which case we need
	 * to mark its parents recursively too..
	 */
	if (commit->object.flags & UNINTERESTING) {
		while (parent) {
			struct commit *p = parent->item;
			parent = parent->next;
			parse_commit(p);
			p->object.flags |= UNINTERESTING;
			if (p->parents)
				mark_parents_uninteresting(p);
			if (p->object.flags & SEEN)
				continue;
			p->object.flags |= SEEN;
			insert_by_date(p, list);
		}
		return;
	}

	/*
	 * Ok, the commit wasn't uninteresting. Try to
	 * simplify the commit history and find the parent
	 * that has no differences in the path set if one exists.
	 */
	if (revs->prune_fn)
		revs->prune_fn(revs, commit);

	if (revs->no_walk)
		return;

	left_flag = (commit->object.flags & SYMMETRIC_LEFT);
	parent = commit->parents;
	while (parent) {
		struct commit *p = parent->item;

		parent = parent->next;

		parse_commit(p);
		p->object.flags |= left_flag;
		if (p->object.flags & SEEN)
			continue;
		p->object.flags |= SEEN;
		insert_by_date(p, list);
	}
}

static void limit_list(struct rev_info *revs)
{
	struct commit_list *list = revs->commits;
	struct commit_list *newlist = NULL;
	struct commit_list **p = &newlist;

	while (list) {
		struct commit_list *entry = list;
		struct commit *commit = list->item;
		struct object *obj = &commit->object;

		list = list->next;
		free(entry);

		if (revs->max_age != -1 && (commit->date < revs->max_age))
			obj->flags |= UNINTERESTING;
		add_parents_to_list(revs, commit, &list);
		if (obj->flags & UNINTERESTING) {
			mark_parents_uninteresting(commit);
			if (everybody_uninteresting(list))
				break;
			continue;
		}
		if (revs->min_age != -1 && (commit->date > revs->min_age))
			continue;
		p = &commit_list_insert(commit, p)->next;
	}
	if (revs->boundary) {
		/* mark the ones that are on the result list first */
		for (list = newlist; list; list = list->next) {
			struct commit *commit = list->item;
			commit->object.flags |= TMP_MARK;
		}
		for (list = newlist; list; list = list->next) {
			struct commit *commit = list->item;
			struct object *obj = &commit->object;
			struct commit_list *parent;
			if (obj->flags & UNINTERESTING)
				continue;
			for (parent = commit->parents;
			     parent;
			     parent = parent->next) {
				struct commit *pcommit = parent->item;
				if (!(pcommit->object.flags & UNINTERESTING))
					continue;
				pcommit->object.flags |= BOUNDARY;
				if (pcommit->object.flags & TMP_MARK)
					continue;
				pcommit->object.flags |= TMP_MARK;
				p = &commit_list_insert(pcommit, p)->next;
			}
		}
		for (list = newlist; list; list = list->next) {
			struct commit *commit = list->item;
			commit->object.flags &= ~TMP_MARK;
		}
	}
	revs->commits = newlist;
}

struct all_refs_cb {
	int all_flags;
	int warned_bad_reflog;
	struct rev_info *all_revs;
	const char *name_for_errormsg;
};

static int handle_one_ref(const char *path, const unsigned char *sha1, int flag, void *cb_data)
{
	struct all_refs_cb *cb = cb_data;
	struct object *object = get_reference(cb->all_revs, path, sha1,
					      cb->all_flags);
	add_pending_object(cb->all_revs, object, "");
	return 0;
}

static void handle_all(struct rev_info *revs, unsigned flags)
{
	struct all_refs_cb cb;
	cb.all_revs = revs;
	cb.all_flags = flags;
	for_each_ref(handle_one_ref, &cb);
}

static void handle_one_reflog_commit(unsigned char *sha1, void *cb_data)
{
	struct all_refs_cb *cb = cb_data;
	if (!is_null_sha1(sha1)) {
		struct object *o = parse_object(sha1);
		if (o) {
			o->flags |= cb->all_flags;
			add_pending_object(cb->all_revs, o, "");
		}
		else if (!cb->warned_bad_reflog) {
			warn("reflog of '%s' references pruned commits",
				cb->name_for_errormsg);
			cb->warned_bad_reflog = 1;
		}
	}
}

static int handle_one_reflog_ent(unsigned char *osha1, unsigned char *nsha1, char *detail, void *cb_data)
{
	handle_one_reflog_commit(osha1, cb_data);
	handle_one_reflog_commit(nsha1, cb_data);
	return 0;
}

static int handle_one_reflog(const char *path, const unsigned char *sha1, int flag, void *cb_data)
{
	struct all_refs_cb *cb = cb_data;
	cb->warned_bad_reflog = 0;
	cb->name_for_errormsg = path;
	for_each_reflog_ent(path, handle_one_reflog_ent, cb_data);
	return 0;
}

static void handle_reflog(struct rev_info *revs, unsigned flags)
{
	struct all_refs_cb cb;
	cb.all_revs = revs;
	cb.all_flags = flags;
	for_each_ref(handle_one_reflog, &cb);
}

static int add_parents_only(struct rev_info *revs, const char *arg, int flags)
{
	unsigned char sha1[20];
	struct object *it;
	struct commit *commit;
	struct commit_list *parents;

	if (*arg == '^') {
		flags ^= UNINTERESTING;
		arg++;
	}
	if (get_sha1(arg, sha1))
		return 0;
	while (1) {
		it = get_reference(revs, arg, sha1, 0);
		if (it->type != OBJ_TAG)
			break;
		hashcpy(sha1, ((struct tag*)it)->tagged->sha1);
	}
	if (it->type != OBJ_COMMIT)
		return 0;
	commit = (struct commit *)it;
	for (parents = commit->parents; parents; parents = parents->next) {
		it = &parents->item->object;
		it->flags |= flags;
		add_pending_object(revs, it, arg);
	}
	return 1;
}

void init_revisions(struct rev_info *revs, const char *prefix)
{
	memset(revs, 0, sizeof(*revs));

	revs->abbrev = DEFAULT_ABBREV;
	revs->ignore_merges = 1;
	revs->simplify_history = 1;
	revs->pruning.recursive = 1;
	revs->pruning.add_remove = file_add_remove;
	revs->pruning.change = file_change;
	revs->lifo = 1;
	revs->dense = 1;
	revs->prefix = prefix;
	revs->max_age = -1;
	revs->min_age = -1;
	revs->skip_count = -1;
	revs->max_count = -1;

	revs->prune_fn = NULL;
	revs->prune_data = NULL;

	revs->topo_setter = topo_sort_default_setter;
	revs->topo_getter = topo_sort_default_getter;

	revs->commit_format = CMIT_FMT_DEFAULT;

	diff_setup(&revs->diffopt);
}

static void add_pending_commit_list(struct rev_info *revs,
                                    struct commit_list *commit_list,
                                    unsigned int flags)
{
	while (commit_list) {
		struct object *object = &commit_list->item->object;
		object->flags |= flags;
		add_pending_object(revs, object, sha1_to_hex(object->sha1));
		commit_list = commit_list->next;
	}
}

static void prepare_show_merge(struct rev_info *revs)
{
	struct commit_list *bases;
	struct commit *head, *other;
	unsigned char sha1[20];
	const char **prune = NULL;
	int i, prune_num = 1; /* counting terminating NULL */

	if (get_sha1("HEAD", sha1) || !(head = lookup_commit(sha1)))
		die("--merge without HEAD?");
	if (get_sha1("MERGE_HEAD", sha1) || !(other = lookup_commit(sha1)))
		die("--merge without MERGE_HEAD?");
	add_pending_object(revs, &head->object, "HEAD");
	add_pending_object(revs, &other->object, "MERGE_HEAD");
	bases = get_merge_bases(head, other, 1);
	while (bases) {
		struct commit *it = bases->item;
		struct commit_list *n = bases->next;
		free(bases);
		bases = n;
		it->object.flags |= UNINTERESTING;
		add_pending_object(revs, &it->object, "(merge-base)");
	}

	if (!active_nr)
		read_cache();
	for (i = 0; i < active_nr; i++) {
		struct cache_entry *ce = active_cache[i];
		if (!ce_stage(ce))
			continue;
		if (ce_path_match(ce, revs->prune_data)) {
			prune_num++;
			prune = xrealloc(prune, sizeof(*prune) * prune_num);
			prune[prune_num-2] = ce->name;
			prune[prune_num-1] = NULL;
		}
		while ((i+1 < active_nr) &&
		       ce_same_name(ce, active_cache[i+1]))
			i++;
	}
	revs->prune_data = prune;
}

int handle_revision_arg(const char *arg, struct rev_info *revs,
			int flags,
			int cant_be_filename)
{
	char *dotdot;
	struct object *object;
	unsigned char sha1[20];
	int local_flags;

	dotdot = strstr(arg, "..");
	if (dotdot) {
		unsigned char from_sha1[20];
		const char *next = dotdot + 2;
		const char *this = arg;
		int symmetric = *next == '.';
		unsigned int flags_exclude = flags ^ UNINTERESTING;

		*dotdot = 0;
		next += symmetric;

		if (!*next)
			next = "HEAD";
		if (dotdot == arg)
			this = "HEAD";
		if (!get_sha1(this, from_sha1) &&
		    !get_sha1(next, sha1)) {
			struct commit *a, *b;
			struct commit_list *exclude;

			a = lookup_commit_reference(from_sha1);
			b = lookup_commit_reference(sha1);
			if (!a || !b) {
				die(symmetric ?
				    "Invalid symmetric difference expression %s...%s" :
				    "Invalid revision range %s..%s",
				    arg, next);
			}

			if (!cant_be_filename) {
				*dotdot = '.';
				verify_non_filename(revs->prefix, arg);
			}

			if (symmetric) {
				exclude = get_merge_bases(a, b, 1);
				add_pending_commit_list(revs, exclude,
							flags_exclude);
				free_commit_list(exclude);
				a->object.flags |= flags | SYMMETRIC_LEFT;
			} else
				a->object.flags |= flags_exclude;
			b->object.flags |= flags;
			add_pending_object(revs, &a->object, this);
			add_pending_object(revs, &b->object, next);
			return 0;
		}
		*dotdot = '.';
	}
	dotdot = strstr(arg, "^@");
	if (dotdot && !dotdot[2]) {
		*dotdot = 0;
		if (add_parents_only(revs, arg, flags))
			return 0;
		*dotdot = '^';
	}
	dotdot = strstr(arg, "^!");
	if (dotdot && !dotdot[2]) {
		*dotdot = 0;
		if (!add_parents_only(revs, arg, flags ^ UNINTERESTING))
			*dotdot = '^';
	}

	local_flags = 0;
	if (*arg == '^') {
		local_flags = UNINTERESTING;
		arg++;
	}
	if (get_sha1(arg, sha1))
		return -1;
	if (!cant_be_filename)
		verify_non_filename(revs->prefix, arg);
	object = get_reference(revs, arg, sha1, flags ^ local_flags);
	add_pending_object(revs, object, arg);
	return 0;
}

static void add_grep(struct rev_info *revs, const char *ptn, enum grep_pat_token what)
{
	if (!revs->grep_filter) {
		struct grep_opt *opt = xcalloc(1, sizeof(*opt));
		opt->status_only = 1;
		opt->pattern_tail = &(opt->pattern_list);
		opt->regflags = REG_NEWLINE;
		revs->grep_filter = opt;
	}
	append_grep_pattern(revs->grep_filter, ptn,
			    "command line", 0, what);
}

static void add_header_grep(struct rev_info *revs, const char *field, const char *pattern)
{
	char *pat;
	const char *prefix;
	int patlen, fldlen;

	fldlen = strlen(field);
	patlen = strlen(pattern);
	pat = xmalloc(patlen + fldlen + 10);
	prefix = ".*";
	if (*pattern == '^') {
		prefix = "";
		pattern++;
	}
	sprintf(pat, "^%s %s%s", field, prefix, pattern);
	add_grep(revs, pat, GREP_PATTERN_HEAD);
}

static void add_message_grep(struct rev_info *revs, const char *pattern)
{
	add_grep(revs, pattern, GREP_PATTERN_BODY);
}

static void add_ignore_packed(struct rev_info *revs, const char *name)
{
	int num = ++revs->num_ignore_packed;

	revs->ignore_packed = xrealloc(revs->ignore_packed,
				       sizeof(const char **) * (num + 1));
	revs->ignore_packed[num-1] = name;
	revs->ignore_packed[num] = NULL;
}

/*
 * Parse revision information, filling in the "rev_info" structure,
 * and removing the used arguments from the argument list.
 *
 * Returns the number of arguments left that weren't recognized
 * (which are also moved to the head of the argument list)
 */
int setup_revisions(int argc, const char **argv, struct rev_info *revs, const char *def)
{
	int i, flags, seen_dashdash, show_merge;
	const char **unrecognized = argv + 1;
	int left = 1;
	int all_match = 0;

	/* First, search for "--" */
	seen_dashdash = 0;
	for (i = 1; i < argc; i++) {
		const char *arg = argv[i];
		if (strcmp(arg, "--"))
			continue;
		argv[i] = NULL;
		argc = i;
		revs->prune_data = get_pathspec(revs->prefix, argv + i + 1);
		seen_dashdash = 1;
		break;
	}

	flags = show_merge = 0;
	for (i = 1; i < argc; i++) {
		const char *arg = argv[i];
		if (*arg == '-') {
			int opts;
			if (!strncmp(arg, "--max-count=", 12)) {
				revs->max_count = atoi(arg + 12);
				continue;
			}
			if (!strncmp(arg, "--skip=", 7)) {
				revs->skip_count = atoi(arg + 7);
				continue;
			}
			/* accept -<digit>, like traditional "head" */
			if ((*arg == '-') && isdigit(arg[1])) {
				revs->max_count = atoi(arg + 1);
				continue;
			}
			if (!strcmp(arg, "-n")) {
				if (argc <= i + 1)
					die("-n requires an argument");
				revs->max_count = atoi(argv[++i]);
				continue;
			}
			if (!strncmp(arg,"-n",2)) {
				revs->max_count = atoi(arg + 2);
				continue;
			}
			if (!strncmp(arg, "--max-age=", 10)) {
				revs->max_age = atoi(arg + 10);
				continue;
			}
			if (!strncmp(arg, "--since=", 8)) {
				revs->max_age = approxidate(arg + 8);
				continue;
			}
			if (!strncmp(arg, "--after=", 8)) {
				revs->max_age = approxidate(arg + 8);
				continue;
			}
			if (!strncmp(arg, "--min-age=", 10)) {
				revs->min_age = atoi(arg + 10);
				continue;
			}
			if (!strncmp(arg, "--before=", 9)) {
				revs->min_age = approxidate(arg + 9);
				continue;
			}
			if (!strncmp(arg, "--until=", 8)) {
				revs->min_age = approxidate(arg + 8);
				continue;
			}
			if (!strcmp(arg, "--all")) {
				handle_all(revs, flags);
				continue;
			}
			if (!strcmp(arg, "--reflog")) {
				handle_reflog(revs, flags);
				continue;
			}
			if (!strcmp(arg, "--not")) {
				flags ^= UNINTERESTING;
				continue;
			}
			if (!strcmp(arg, "--default")) {
				if (++i >= argc)
					die("bad --default argument");
				def = argv[i];
				continue;
			}
			if (!strcmp(arg, "--merge")) {
				show_merge = 1;
				continue;
			}
			if (!strcmp(arg, "--topo-order")) {
				revs->topo_order = 1;
				continue;
			}
			if (!strcmp(arg, "--date-order")) {
				revs->lifo = 0;
				revs->topo_order = 1;
				continue;
			}
			if (!strcmp(arg, "--parents")) {
				revs->parents = 1;
				continue;
			}
			if (!strcmp(arg, "--dense")) {
				revs->dense = 1;
				continue;
			}
			if (!strcmp(arg, "--sparse")) {
				revs->dense = 0;
				continue;
			}
			if (!strcmp(arg, "--remove-empty")) {
				revs->remove_empty_trees = 1;
				continue;
			}
			if (!strcmp(arg, "--no-merges")) {
				revs->no_merges = 1;
				continue;
			}
			if (!strcmp(arg, "--boundary")) {
				revs->boundary = 1;
				continue;
			}
			if (!strcmp(arg, "--left-right")) {
				revs->left_right = 1;
				continue;
			}
			if (!strcmp(arg, "--objects")) {
				revs->tag_objects = 1;
				revs->tree_objects = 1;
				revs->blob_objects = 1;
				continue;
			}
			if (!strcmp(arg, "--objects-edge")) {
				revs->tag_objects = 1;
				revs->tree_objects = 1;
				revs->blob_objects = 1;
				revs->edge_hint = 1;
				continue;
			}
			if (!strcmp(arg, "--unpacked")) {
				revs->unpacked = 1;
				free(revs->ignore_packed);
				revs->ignore_packed = NULL;
				revs->num_ignore_packed = 0;
				continue;
			}
			if (!strncmp(arg, "--unpacked=", 11)) {
				revs->unpacked = 1;
				add_ignore_packed(revs, arg+11);
				continue;
			}
			if (!strcmp(arg, "-r")) {
				revs->diff = 1;
				revs->diffopt.recursive = 1;
				continue;
			}
			if (!strcmp(arg, "-t")) {
				revs->diff = 1;
				revs->diffopt.recursive = 1;
				revs->diffopt.tree_in_recursive = 1;
				continue;
			}
			if (!strcmp(arg, "-m")) {
				revs->ignore_merges = 0;
				continue;
			}
			if (!strcmp(arg, "-c")) {
				revs->diff = 1;
				revs->dense_combined_merges = 0;
				revs->combine_merges = 1;
				continue;
			}
			if (!strcmp(arg, "--cc")) {
				revs->diff = 1;
				revs->dense_combined_merges = 1;
				revs->combine_merges = 1;
				continue;
			}
			if (!strcmp(arg, "-v")) {
				revs->verbose_header = 1;
				continue;
			}
			if (!strncmp(arg, "--pretty", 8)) {
				revs->verbose_header = 1;
				revs->commit_format = get_commit_format(arg+8);
				continue;
			}
			if (!strcmp(arg, "--root")) {
				revs->show_root_diff = 1;
				continue;
			}
			if (!strcmp(arg, "--no-commit-id")) {
				revs->no_commit_id = 1;
				continue;
			}
			if (!strcmp(arg, "--always")) {
				revs->always_show_header = 1;
				continue;
			}
			if (!strcmp(arg, "--no-abbrev")) {
				revs->abbrev = 0;
				continue;
			}
			if (!strcmp(arg, "--abbrev")) {
				revs->abbrev = DEFAULT_ABBREV;
				continue;
			}
			if (!strncmp(arg, "--abbrev=", 9)) {
				revs->abbrev = strtoul(arg + 9, NULL, 10);
				if (revs->abbrev < MINIMUM_ABBREV)
					revs->abbrev = MINIMUM_ABBREV;
				else if (revs->abbrev > 40)
					revs->abbrev = 40;
				continue;
			}
			if (!strcmp(arg, "--abbrev-commit")) {
				revs->abbrev_commit = 1;
				continue;
			}
			if (!strcmp(arg, "--full-diff")) {
				revs->diff = 1;
				revs->full_diff = 1;
				continue;
			}
			if (!strcmp(arg, "--full-history")) {
				revs->simplify_history = 0;
				continue;
			}
			if (!strcmp(arg, "--relative-date")) {
				revs->relative_date = 1;
				continue;
			}

			/*
			 * Grepping the commit log
			 */
			if (!strncmp(arg, "--author=", 9)) {
				add_header_grep(revs, "author", arg+9);
				continue;
			}
			if (!strncmp(arg, "--committer=", 12)) {
				add_header_grep(revs, "committer", arg+12);
				continue;
			}
			if (!strncmp(arg, "--grep=", 7)) {
				add_message_grep(revs, arg+7);
				continue;
			}
			if (!strcmp(arg, "--all-match")) {
				all_match = 1;
				continue;
			}
			if (!strncmp(arg, "--encoding=", 11)) {
				arg += 11;
				if (strcmp(arg, "none"))
					git_log_output_encoding = strdup(arg);
				else
					git_log_output_encoding = "";
				continue;
			}

			opts = diff_opt_parse(&revs->diffopt, argv+i, argc-i);
			if (opts > 0) {
				revs->diff = 1;
				i += opts - 1;
				continue;
			}
			*unrecognized++ = arg;
			left++;
			continue;
		}

		if (handle_revision_arg(arg, revs, flags, seen_dashdash)) {
			int j;
			if (seen_dashdash || *arg == '^')
				die("bad revision '%s'", arg);

			/* If we didn't have a "--":
			 * (1) all filenames must exist;
			 * (2) all rev-args must not be interpretable
			 *     as a valid filename.
			 * but the latter we have checked in the main loop.
			 */
			for (j = i; j < argc; j++)
				verify_filename(revs->prefix, argv[j]);

			revs->prune_data = get_pathspec(revs->prefix,
							argv + i);
			break;
		}
	}

	if (show_merge)
		prepare_show_merge(revs);
	if (def && !revs->pending.nr) {
		unsigned char sha1[20];
		struct object *object;
		if (get_sha1(def, sha1))
			die("bad default revision '%s'", def);
		object = get_reference(revs, def, sha1, 0);
		add_pending_object(revs, object, def);
	}

	if (revs->topo_order)
		revs->limited = 1;

	if (revs->prune_data) {
		diff_tree_setup_paths(revs->prune_data, &revs->pruning);
		revs->prune_fn = try_to_simplify_commit;
		if (!revs->full_diff)
			diff_tree_setup_paths(revs->prune_data, &revs->diffopt);
	}
	if (revs->combine_merges) {
		revs->ignore_merges = 0;
		if (revs->dense_combined_merges && !revs->diffopt.output_format)
			revs->diffopt.output_format = DIFF_FORMAT_PATCH;
	}
	revs->diffopt.abbrev = revs->abbrev;
	if (diff_setup_done(&revs->diffopt) < 0)
		die("diff_setup_done failed");

	if (revs->grep_filter) {
		revs->grep_filter->all_match = all_match;
		compile_grep_patterns(revs->grep_filter);
	}

	return left;
}

void prepare_revision_walk(struct rev_info *revs)
{
	int nr = revs->pending.nr;
	struct object_array_entry *list = revs->pending.objects;

	revs->pending.nr = 0;
	revs->pending.alloc = 0;
	revs->pending.objects = NULL;
	while (--nr >= 0) {
		struct commit *commit = handle_commit(revs, list->item, list->name);
		if (commit) {
			if (!(commit->object.flags & SEEN)) {
				commit->object.flags |= SEEN;
				insert_by_date(commit, &revs->commits);
			}
		}
		list++;
	}

	if (revs->no_walk)
		return;
	if (revs->limited)
		limit_list(revs);
	if (revs->topo_order)
		sort_in_topological_order_fn(&revs->commits, revs->lifo,
					     revs->topo_setter,
					     revs->topo_getter);
}

static int rewrite_one(struct rev_info *revs, struct commit **pp)
{
	for (;;) {
		struct commit *p = *pp;
		if (!revs->limited)
			add_parents_to_list(revs, p, &revs->commits);
		if (p->parents && p->parents->next)
			return 0;
		if (p->object.flags & (TREECHANGE | UNINTERESTING))
			return 0;
		if (!p->parents)
			return -1;
		*pp = p->parents->item;
	}
}

static void rewrite_parents(struct rev_info *revs, struct commit *commit)
{
	struct commit_list **pp = &commit->parents;
	while (*pp) {
		struct commit_list *parent = *pp;
		if (rewrite_one(revs, &parent->item) < 0) {
			*pp = parent->next;
			continue;
		}
		pp = &parent->next;
	}
}

static void mark_boundary_to_show(struct commit *commit)
{
	struct commit_list *p = commit->parents;
	while (p) {
		commit = p->item;
		p = p->next;
		if (commit->object.flags & BOUNDARY)
			commit->object.flags |= BOUNDARY_SHOW;
	}
}

static int commit_match(struct commit *commit, struct rev_info *opt)
{
	if (!opt->grep_filter)
		return 1;
	return grep_buffer(opt->grep_filter,
			   NULL, /* we say nothing, not even filename */
			   commit->buffer, strlen(commit->buffer));
}

static struct commit *get_revision_1(struct rev_info *revs)
{
	if (!revs->commits)
		return NULL;

	do {
		struct commit_list *entry = revs->commits;
		struct commit *commit = entry->item;

		revs->commits = entry->next;
		free(entry);

		/*
		 * If we haven't done the list limiting, we need to look at
		 * the parents here. We also need to do the date-based limiting
		 * that we'd otherwise have done in limit_list().
		 */
		if (!revs->limited) {
			if (revs->max_age != -1 &&
			    (commit->date < revs->max_age))
				continue;
			add_parents_to_list(revs, commit, &revs->commits);
		}
		if (commit->object.flags & SHOWN)
			continue;

		if (revs->unpacked && has_sha1_pack(commit->object.sha1,
						    revs->ignore_packed))
		    continue;

		/* We want to show boundary commits only when their
		 * children are shown.  When path-limiter is in effect,
		 * rewrite_parents() drops some commits from getting shown,
		 * and there is no point showing boundary parents that
		 * are not shown.  After rewrite_parents() rewrites the
		 * parents of a commit that is shown, we mark the boundary
		 * parents with BOUNDARY_SHOW.
		 */
		if (commit->object.flags & BOUNDARY_SHOW) {
			commit->object.flags |= SHOWN;
			return commit;
		}
		if (commit->object.flags & UNINTERESTING)
			continue;
		if (revs->min_age != -1 && (commit->date > revs->min_age))
			continue;
		if (revs->no_merges &&
		    commit->parents && commit->parents->next)
			continue;
		if (!commit_match(commit, revs))
			continue;
		if (revs->prune_fn && revs->dense) {
			/* Commit without changes? */
			if (!(commit->object.flags & TREECHANGE)) {
				/* drop merges unless we want parenthood */
				if (!revs->parents)
					continue;
				/* non-merge - always ignore it */
				if (!commit->parents || !commit->parents->next)
					continue;
			}
			if (revs->parents)
				rewrite_parents(revs, commit);
		}
		if (revs->boundary)
			mark_boundary_to_show(commit);
		commit->object.flags |= SHOWN;
		return commit;
	} while (revs->commits);
	return NULL;
}

struct commit *get_revision(struct rev_info *revs)
{
	struct commit *c = NULL;

	if (0 < revs->skip_count) {
		while ((c = get_revision_1(revs)) != NULL) {
			if (revs->skip_count-- <= 0)
				break;
		}
	}

	/* Check the max_count ... */
	switch (revs->max_count) {
	case -1:
		break;
	case 0:
		return NULL;
	default:
		revs->max_count--;
	}
	if (c)
		return c;
	return get_revision_1(revs);
}