git-cvsserver: add ability to guess -kb from contents

[thirdparty/git.git] / diff-lib.c

/*
 * Copyright (C) 2005 Junio C Hamano
 */
#include "cache.h"
#include "quote.h"
#include "commit.h"
#include "diff.h"
#include "diffcore.h"
#include "revision.h"
#include "cache-tree.h"
#include "path-list.h"
#include "unpack-trees.h"
#include "refs.h"

/*
 * diff-files
 */

static int read_directory(const char *path, struct path_list *list)
{
	DIR *dir;
	struct dirent *e;

	if (!(dir = opendir(path)))
		return error("Could not open directory %s", path);

	while ((e = readdir(dir)))
		if (strcmp(".", e->d_name) && strcmp("..", e->d_name))
			path_list_insert(e->d_name, list);

	closedir(dir);
	return 0;
}

static int get_mode(const char *path, int *mode)
{
	struct stat st;

	if (!path || !strcmp(path, "/dev/null"))
		*mode = 0;
	else if (!strcmp(path, "-"))
		*mode = create_ce_mode(0666);
	else if (stat(path, &st))
		return error("Could not access '%s'", path);
	else
		*mode = st.st_mode;
	return 0;
}

static int queue_diff(struct diff_options *o,
		const char *name1, const char *name2)
{
	int mode1 = 0, mode2 = 0;

	if (get_mode(name1, &mode1) || get_mode(name2, &mode2))
		return -1;

	if (mode1 && mode2 && S_ISDIR(mode1) != S_ISDIR(mode2))
		return error("file/directory conflict: %s, %s", name1, name2);

	if (S_ISDIR(mode1) || S_ISDIR(mode2)) {
		char buffer1[PATH_MAX], buffer2[PATH_MAX];
		struct path_list p1 = {NULL, 0, 0, 1}, p2 = {NULL, 0, 0, 1};
		int len1 = 0, len2 = 0, i1, i2, ret = 0;

		if (name1 && read_directory(name1, &p1))
			return -1;
		if (name2 && read_directory(name2, &p2)) {
			path_list_clear(&p1, 0);
			return -1;
		}

		if (name1) {
			len1 = strlen(name1);
			if (len1 > 0 && name1[len1 - 1] == '/')
				len1--;
			memcpy(buffer1, name1, len1);
			buffer1[len1++] = '/';
		}

		if (name2) {
			len2 = strlen(name2);
			if (len2 > 0 && name2[len2 - 1] == '/')
				len2--;
			memcpy(buffer2, name2, len2);
			buffer2[len2++] = '/';
		}

		for (i1 = i2 = 0; !ret && (i1 < p1.nr || i2 < p2.nr); ) {
			const char *n1, *n2;
			int comp;

			if (i1 == p1.nr)
				comp = 1;
			else if (i2 == p2.nr)
				comp = -1;
			else
				comp = strcmp(p1.items[i1].path,
					p2.items[i2].path);

			if (comp > 0)
				n1 = NULL;
			else {
				n1 = buffer1;
				strncpy(buffer1 + len1, p1.items[i1++].path,
						PATH_MAX - len1);
			}

			if (comp < 0)
				n2 = NULL;
			else {
				n2 = buffer2;
				strncpy(buffer2 + len2, p2.items[i2++].path,
						PATH_MAX - len2);
			}

			ret = queue_diff(o, n1, n2);
		}
		path_list_clear(&p1, 0);
		path_list_clear(&p2, 0);

		return ret;
	} else {
		struct diff_filespec *d1, *d2;

		if (DIFF_OPT_TST(o, REVERSE_DIFF)) {
			unsigned tmp;
			const char *tmp_c;
			tmp = mode1; mode1 = mode2; mode2 = tmp;
			tmp_c = name1; name1 = name2; name2 = tmp_c;
		}

		if (!name1)
			name1 = "/dev/null";
		if (!name2)
			name2 = "/dev/null";
		d1 = alloc_filespec(name1);
		d2 = alloc_filespec(name2);
		fill_filespec(d1, null_sha1, mode1);
		fill_filespec(d2, null_sha1, mode2);

		diff_queue(&diff_queued_diff, d1, d2);
		return 0;
	}
}

/*
 * Does the path name a blob in the working tree, or a directory
 * in the working tree?
 */
static int is_in_index(const char *path)
{
	int len, pos;
	struct cache_entry *ce;

	len = strlen(path);
	while (path[len-1] == '/')
		len--;
	if (!len)
		return 1; /* "." */
	pos = cache_name_pos(path, len);
	if (0 <= pos)
		return 1;
	pos = -1 - pos;
	while (pos < active_nr) {
		ce = active_cache[pos++];
		if (ce_namelen(ce) <= len ||
		    strncmp(ce->name, path, len) ||
		    (ce->name[len] > '/'))
			break; /* path cannot be a prefix */
		if (ce->name[len] == '/')
			return 1;
	}
	return 0;
}

static int handle_diff_files_args(struct rev_info *revs,
				  int argc, const char **argv,
				  unsigned int *options)
{
	*options = 0;

	/* revs->max_count == -2 means --no-index */
	while (1 < argc && argv[1][0] == '-') {
		if (!strcmp(argv[1], "--base"))
			revs->max_count = 1;
		else if (!strcmp(argv[1], "--ours"))
			revs->max_count = 2;
		else if (!strcmp(argv[1], "--theirs"))
			revs->max_count = 3;
		else if (!strcmp(argv[1], "-n") ||
				!strcmp(argv[1], "--no-index")) {
			revs->max_count = -2;
			DIFF_OPT_SET(&revs->diffopt, EXIT_WITH_STATUS);
			DIFF_OPT_SET(&revs->diffopt, NO_INDEX);
		}
		else if (!strcmp(argv[1], "-q"))
			*options |= DIFF_SILENT_ON_REMOVED;
		else
			return error("invalid option: %s", argv[1]);
		argv++; argc--;
	}

	if (revs->max_count == -1 && revs->diffopt.nr_paths == 2) {
		/*
		 * If two files are specified, and at least one is untracked,
		 * default to no-index.
		 */
		read_cache();
		if (!is_in_index(revs->diffopt.paths[0]) ||
					!is_in_index(revs->diffopt.paths[1])) {
			revs->max_count = -2;
			DIFF_OPT_SET(&revs->diffopt, NO_INDEX);
		}
	}

	/*
	 * Make sure there are NO revision (i.e. pending object) parameter,
	 * rev.max_count is reasonable (0 <= n <= 3),
	 * there is no other revision filtering parameters.
	 */
	if (revs->pending.nr || revs->max_count > 3 ||
	    revs->min_age != -1 || revs->max_age != -1)
		return error("no revision allowed with diff-files");

	if (revs->max_count == -1 &&
	    (revs->diffopt.output_format & DIFF_FORMAT_PATCH))
		revs->combine_merges = revs->dense_combined_merges = 1;

	return 0;
}

static int is_outside_repo(const char *path, int nongit, const char *prefix)
{
	int i;
	if (nongit || !strcmp(path, "-") || is_absolute_path(path))
		return 1;
	if (prefixcmp(path, "../"))
		return 0;
	if (!prefix)
		return 1;
	for (i = strlen(prefix); !prefixcmp(path, "../"); ) {
		while (i > 0 && prefix[i - 1] != '/')
			i--;
		if (--i < 0)
			return 1;
		path += 3;
	}
	return 0;
}

int setup_diff_no_index(struct rev_info *revs,
		int argc, const char ** argv, int nongit, const char *prefix)
{
	int i;
	for (i = 1; i < argc; i++)
		if (argv[i][0] != '-' || argv[i][1] == '\0')
			break;
		else if (!strcmp(argv[i], "--")) {
			i++;
			break;
		} else if (i < argc - 3 && !strcmp(argv[i], "--no-index")) {
			i = argc - 3;
			DIFF_OPT_SET(&revs->diffopt, EXIT_WITH_STATUS);
			break;
		}
	if (nongit && argc != i + 2)
		die("git diff [--no-index] takes two paths");

	if (argc != i + 2 || (!is_outside_repo(argv[i + 1], nongit, prefix) &&
				!is_outside_repo(argv[i], nongit, prefix)))
		return -1;

	diff_setup(&revs->diffopt);
	for (i = 1; i < argc - 2; )
		if (!strcmp(argv[i], "--no-index"))
			i++;
		else {
			int j = diff_opt_parse(&revs->diffopt,
					argv + i, argc - i);
			if (!j)
				die("invalid diff option/value: %s", argv[i]);
			i += j;
		}

	if (prefix) {
		int len = strlen(prefix);

		revs->diffopt.paths = xcalloc(2, sizeof(char*));
		for (i = 0; i < 2; i++) {
			const char *p = argv[argc - 2 + i];
			/*
			 * stdin should be spelled as '-'; if you have
			 * path that is '-', spell it as ./-.
			 */
			p = (strcmp(p, "-")
			     ? xstrdup(prefix_filename(prefix, len, p))
			     : p);
			revs->diffopt.paths[i] = p;
		}
	}
	else
		revs->diffopt.paths = argv + argc - 2;
	revs->diffopt.nr_paths = 2;
	DIFF_OPT_SET(&revs->diffopt, NO_INDEX);
	revs->max_count = -2;
	if (diff_setup_done(&revs->diffopt) < 0)
		die("diff_setup_done failed");
	return 0;
}

int run_diff_files_cmd(struct rev_info *revs, int argc, const char **argv)
{
	unsigned int options;

	if (handle_diff_files_args(revs, argc, argv, &options))
		return -1;

	if (DIFF_OPT_TST(&revs->diffopt, NO_INDEX)) {
		if (revs->diffopt.nr_paths != 2)
			return error("need two files/directories with --no-index");
		if (queue_diff(&revs->diffopt, revs->diffopt.paths[0],
				revs->diffopt.paths[1]))
			return -1;
		diffcore_std(&revs->diffopt);
		diff_flush(&revs->diffopt);
		/*
		 * The return code for --no-index imitates diff(1):
		 * 0 = no changes, 1 = changes, else error
		 */
		return revs->diffopt.found_changes;
	}

	if (read_cache() < 0) {
		perror("read_cache");
		return -1;
	}
	return run_diff_files(revs, options);
}

/*
 * Has the work tree entity been removed?
 *
 * Return 1 if it was removed from the work tree, 0 if an entity to be
 * compared with the cache entry ce still exists (the latter includes
 * the case where a directory that is not a submodule repository
 * exists for ce that is a submodule -- it is a submodule that is not
 * checked out).  Return negative for an error.
 */
static int check_removed(const struct cache_entry *ce, struct stat *st)
{
	if (lstat(ce->name, st) < 0) {
		if (errno != ENOENT && errno != ENOTDIR)
			return -1;
		return 1;
	}
	if (has_symlink_leading_path(ce_namelen(ce), ce->name))
		return 1;
	if (S_ISDIR(st->st_mode)) {
		unsigned char sub[20];

		/*
		 * If ce is already a gitlink, we can have a plain
		 * directory (i.e. the submodule is not checked out),
		 * or a checked out submodule.  Either case this is not
		 * a case where something was removed from the work tree,
		 * so we will return 0.
		 *
		 * Otherwise, if the directory is not a submodule
		 * repository, that means ce which was a blob turned into
		 * a directory --- the blob was removed!
		 */
		if (!S_ISGITLINK(ce->ce_mode) &&
		    resolve_gitlink_ref(ce->name, "HEAD", sub))
			return 1;
	}
	return 0;
}

int run_diff_files(struct rev_info *revs, unsigned int option)
{
	int entries, i;
	int diff_unmerged_stage = revs->max_count;
	int silent_on_removed = option & DIFF_SILENT_ON_REMOVED;
	unsigned ce_option = ((option & DIFF_RACY_IS_MODIFIED)
			      ? CE_MATCH_RACY_IS_DIRTY : 0);
	char symcache[PATH_MAX];

	if (diff_unmerged_stage < 0)
		diff_unmerged_stage = 2;
	entries = active_nr;
	symcache[0] = '\0';
	for (i = 0; i < entries; i++) {
		struct stat st;
		unsigned int oldmode, newmode;
		struct cache_entry *ce = active_cache[i];
		int changed;

		if (DIFF_OPT_TST(&revs->diffopt, QUIET) &&
			DIFF_OPT_TST(&revs->diffopt, HAS_CHANGES))
			break;

		if (!ce_path_match(ce, revs->prune_data))
			continue;

		if (ce_stage(ce)) {
			struct combine_diff_path *dpath;
			int num_compare_stages = 0;
			size_t path_len;

			path_len = ce_namelen(ce);

			dpath = xmalloc(combine_diff_path_size(5, path_len));
			dpath->path = (char *) &(dpath->parent[5]);

			dpath->next = NULL;
			dpath->len = path_len;
			memcpy(dpath->path, ce->name, path_len);
			dpath->path[path_len] = '\0';
			hashclr(dpath->sha1);
			memset(&(dpath->parent[0]), 0,
			       sizeof(struct combine_diff_parent)*5);

			changed = check_removed(ce, &st);
			if (!changed)
				dpath->mode = ce_mode_from_stat(ce, st.st_mode);
			else {
				if (changed < 0) {
					perror(ce->name);
					continue;
				}
				if (silent_on_removed)
					continue;
			}

			while (i < entries) {
				struct cache_entry *nce = active_cache[i];
				int stage;

				if (strcmp(ce->name, nce->name))
					break;

				/* Stage #2 (ours) is the first parent,
				 * stage #3 (theirs) is the second.
				 */
				stage = ce_stage(nce);
				if (2 <= stage) {
					int mode = nce->ce_mode;
					num_compare_stages++;
					hashcpy(dpath->parent[stage-2].sha1, nce->sha1);
					dpath->parent[stage-2].mode = ce_mode_from_stat(nce, mode);
					dpath->parent[stage-2].status =
						DIFF_STATUS_MODIFIED;
				}

				/* diff against the proper unmerged stage */
				if (stage == diff_unmerged_stage)
					ce = nce;
				i++;
			}
			/*
			 * Compensate for loop update
			 */
			i--;

			if (revs->combine_merges && num_compare_stages == 2) {
				show_combined_diff(dpath, 2,
						   revs->dense_combined_merges,
						   revs);
				free(dpath);
				continue;
			}
			free(dpath);
			dpath = NULL;

			/*
			 * Show the diff for the 'ce' if we found the one
			 * from the desired stage.
			 */
			diff_unmerge(&revs->diffopt, ce->name, 0, null_sha1);
			if (ce_stage(ce) != diff_unmerged_stage)
				continue;
		}

		if (ce_uptodate(ce))
			continue;

		changed = check_removed(ce, &st);
		if (changed) {
			if (changed < 0) {
				perror(ce->name);
				continue;
			}
			if (silent_on_removed)
				continue;
			diff_addremove(&revs->diffopt, '-', ce->ce_mode,
				       ce->sha1, ce->name, NULL);
			continue;
		}
		changed = ce_match_stat(ce, &st, ce_option);
		if (!changed) {
			ce_mark_uptodate(ce);
			if (!DIFF_OPT_TST(&revs->diffopt, FIND_COPIES_HARDER))
				continue;
		}
		oldmode = ce->ce_mode;
		newmode = ce_mode_from_stat(ce, st.st_mode);
		diff_change(&revs->diffopt, oldmode, newmode,
			    ce->sha1, (changed ? null_sha1 : ce->sha1),
			    ce->name, NULL);

	}
	diffcore_std(&revs->diffopt);
	diff_flush(&revs->diffopt);
	return 0;
}

/*
 * diff-index
 */

struct oneway_unpack_data {
	struct rev_info *revs;
	char symcache[PATH_MAX];
};

/* A file entry went away or appeared */
static void diff_index_show_file(struct rev_info *revs,
				 const char *prefix,
				 struct cache_entry *ce,
				 const unsigned char *sha1, unsigned int mode)
{
	diff_addremove(&revs->diffopt, prefix[0], mode,
		       sha1, ce->name, NULL);
}

static int get_stat_data(struct cache_entry *ce,
			 const unsigned char **sha1p,
			 unsigned int *modep,
			 int cached, int match_missing,
			 struct oneway_unpack_data *cbdata)
{
	const unsigned char *sha1 = ce->sha1;
	unsigned int mode = ce->ce_mode;

	if (!cached) {
		int changed;
		struct stat st;
		changed = check_removed(ce, &st);
		if (changed < 0)
			return -1;
		else if (changed) {
			if (match_missing) {
				*sha1p = sha1;
				*modep = mode;
				return 0;
			}
			return -1;
		}
		changed = ce_match_stat(ce, &st, 0);
		if (changed) {
			mode = ce_mode_from_stat(ce, st.st_mode);
			sha1 = null_sha1;
		}
	}

	*sha1p = sha1;
	*modep = mode;
	return 0;
}

static void show_new_file(struct oneway_unpack_data *cbdata,
			  struct cache_entry *new,
			  int cached, int match_missing)
{
	const unsigned char *sha1;
	unsigned int mode;
	struct rev_info *revs = cbdata->revs;

	/*
	 * New file in the index: it might actually be different in
	 * the working copy.
	 */
	if (get_stat_data(new, &sha1, &mode, cached, match_missing, cbdata) < 0)
		return;

	diff_index_show_file(revs, "+", new, sha1, mode);
}

static int show_modified(struct oneway_unpack_data *cbdata,
			 struct cache_entry *old,
			 struct cache_entry *new,
			 int report_missing,
			 int cached, int match_missing)
{
	unsigned int mode, oldmode;
	const unsigned char *sha1;
	struct rev_info *revs = cbdata->revs;

	if (get_stat_data(new, &sha1, &mode, cached, match_missing, cbdata) < 0) {
		if (report_missing)
			diff_index_show_file(revs, "-", old,
					     old->sha1, old->ce_mode);
		return -1;
	}

	if (revs->combine_merges && !cached &&
	    (hashcmp(sha1, old->sha1) || hashcmp(old->sha1, new->sha1))) {
		struct combine_diff_path *p;
		int pathlen = ce_namelen(new);

		p = xmalloc(combine_diff_path_size(2, pathlen));
		p->path = (char *) &p->parent[2];
		p->next = NULL;
		p->len = pathlen;
		memcpy(p->path, new->name, pathlen);
		p->path[pathlen] = 0;
		p->mode = mode;
		hashclr(p->sha1);
		memset(p->parent, 0, 2 * sizeof(struct combine_diff_parent));
		p->parent[0].status = DIFF_STATUS_MODIFIED;
		p->parent[0].mode = new->ce_mode;
		hashcpy(p->parent[0].sha1, new->sha1);
		p->parent[1].status = DIFF_STATUS_MODIFIED;
		p->parent[1].mode = old->ce_mode;
		hashcpy(p->parent[1].sha1, old->sha1);
		show_combined_diff(p, 2, revs->dense_combined_merges, revs);
		free(p);
		return 0;
	}

	oldmode = old->ce_mode;
	if (mode == oldmode && !hashcmp(sha1, old->sha1) &&
	    !DIFF_OPT_TST(&revs->diffopt, FIND_COPIES_HARDER))
		return 0;

	diff_change(&revs->diffopt, oldmode, mode,
		    old->sha1, sha1, old->name, NULL);
	return 0;
}

/*
 * This turns all merge entries into "stage 3". That guarantees that
 * when we read in the new tree (into "stage 1"), we won't lose sight
 * of the fact that we had unmerged entries.
 */
static void mark_merge_entries(void)
{
	int i;
	for (i = 0; i < active_nr; i++) {
		struct cache_entry *ce = active_cache[i];
		if (!ce_stage(ce))
			continue;
		ce->ce_flags |= CE_STAGEMASK;
	}
}

/*
 * This gets a mix of an existing index and a tree, one pathname entry
 * at a time. The index entry may be a single stage-0 one, but it could
 * also be multiple unmerged entries (in which case idx_pos/idx_nr will
 * give you the position and number of entries in the index).
 */
static void do_oneway_diff(struct unpack_trees_options *o,
	struct cache_entry *idx,
	struct cache_entry *tree)
{
	struct oneway_unpack_data *cbdata = o->unpack_data;
	struct rev_info *revs = cbdata->revs;
	int match_missing, cached;

	/*
	 * Backward compatibility wart - "diff-index -m" does
	 * not mean "do not ignore merges", but "match_missing".
	 *
	 * But with the revision flag parsing, that's found in
	 * "!revs->ignore_merges".
	 */
	cached = o->index_only;
	match_missing = !revs->ignore_merges;

	if (cached && idx && ce_stage(idx)) {
		if (tree)
			diff_unmerge(&revs->diffopt, idx->name, idx->ce_mode, idx->sha1);
		return;
	}

	/*
	 * Something added to the tree?
	 */
	if (!tree) {
		show_new_file(cbdata, idx, cached, match_missing);
		return;
	}

	/*
	 * Something removed from the tree?
	 */
	if (!idx) {
		diff_index_show_file(revs, "-", tree, tree->sha1, tree->ce_mode);
		return;
	}

	/* Show difference between old and new */
	show_modified(cbdata, tree, idx, 1, cached, match_missing);
}

static inline void skip_same_name(struct cache_entry *ce, struct unpack_trees_options *o)
{
	int len = ce_namelen(ce);
	const struct index_state *index = o->src_index;

	while (o->pos < index->cache_nr) {
		struct cache_entry *next = index->cache[o->pos];
		if (len != ce_namelen(next))
			break;
		if (memcmp(ce->name, next->name, len))
			break;
		o->pos++;
	}
}

/*
 * The unpack_trees() interface is designed for merging, so
 * the different source entries are designed primarily for
 * the source trees, with the old index being really mainly
 * used for being replaced by the result.
 *
 * For diffing, the index is more important, and we only have a
 * single tree.
 *
 * We're supposed to return how many index entries we want to skip.
 *
 * This wrapper makes it all more readable, and takes care of all
 * the fairly complex unpack_trees() semantic requirements, including
 * the skipping, the path matching, the type conflict cases etc.
 */
static int oneway_diff(struct cache_entry **src, struct unpack_trees_options *o)
{
	struct cache_entry *idx = src[0];
	struct cache_entry *tree = src[1];
	struct oneway_unpack_data *cbdata = o->unpack_data;
	struct rev_info *revs = cbdata->revs;

	if (idx && ce_stage(idx))
		skip_same_name(idx, o);

	/*
	 * Unpack-trees generates a DF/conflict entry if
	 * there was a directory in the index and a tree
	 * in the tree. From a diff standpoint, that's a
	 * delete of the tree and a create of the file.
	 */
	if (tree == o->df_conflict_entry)
		tree = NULL;

	if (ce_path_match(idx ? idx : tree, revs->prune_data))
		do_oneway_diff(o, idx, tree);

	return 0;
}

int run_diff_index(struct rev_info *revs, int cached)
{
	struct object *ent;
	struct tree *tree;
	const char *tree_name;
	struct unpack_trees_options opts;
	struct tree_desc t;
	struct oneway_unpack_data unpack_cb;

	mark_merge_entries();

	ent = revs->pending.objects[0].item;
	tree_name = revs->pending.objects[0].name;
	tree = parse_tree_indirect(ent->sha1);
	if (!tree)
		return error("bad tree object %s", tree_name);

	unpack_cb.revs = revs;
	unpack_cb.symcache[0] = '\0';
	memset(&opts, 0, sizeof(opts));
	opts.head_idx = 1;
	opts.index_only = cached;
	opts.merge = 1;
	opts.fn = oneway_diff;
	opts.unpack_data = &unpack_cb;
	opts.src_index = &the_index;
	opts.dst_index = NULL;

	init_tree_desc(&t, tree->buffer, tree->size);
	if (unpack_trees(1, &t, &opts))
		exit(128);

	diffcore_std(&revs->diffopt);
	diff_flush(&revs->diffopt);
	return 0;
}

int do_diff_cache(const unsigned char *tree_sha1, struct diff_options *opt)
{
	struct tree *tree;
	struct rev_info revs;
	int i;
	struct cache_entry **dst;
	struct cache_entry *last = NULL;
	struct unpack_trees_options opts;
	struct tree_desc t;
	struct oneway_unpack_data unpack_cb;

	/*
	 * This is used by git-blame to run diff-cache internally;
	 * it potentially needs to repeatedly run this, so we will
	 * start by removing the higher order entries the last round
	 * left behind.
	 */
	dst = active_cache;
	for (i = 0; i < active_nr; i++) {
		struct cache_entry *ce = active_cache[i];
		if (ce_stage(ce)) {
			if (last && !strcmp(ce->name, last->name))
				continue;
			cache_tree_invalidate_path(active_cache_tree,
						   ce->name);
			last = ce;
			ce->ce_flags |= CE_REMOVE;
		}
		*dst++ = ce;
	}
	active_nr = dst - active_cache;

	init_revisions(&revs, NULL);
	revs.prune_data = opt->paths;
	tree = parse_tree_indirect(tree_sha1);
	if (!tree)
		die("bad tree object %s", sha1_to_hex(tree_sha1));

	unpack_cb.revs = &revs;
	unpack_cb.symcache[0] = '\0';
	memset(&opts, 0, sizeof(opts));
	opts.head_idx = 1;
	opts.index_only = 1;
	opts.merge = 1;
	opts.fn = oneway_diff;
	opts.unpack_data = &unpack_cb;
	opts.src_index = &the_index;
	opts.dst_index = &the_index;

	init_tree_desc(&t, tree->buffer, tree->size);
	if (unpack_trees(1, &t, &opts))
		exit(128);
	return 0;
}