text: /*
   * Builtin "git diff"
   *
   * Copyright (c) 2006 Junio C Hamano
   */
  #define USE_THE_INDEX_COMPATIBILITY_MACROS
  #include "cache.h"
  #include "config.h"
  #include "ewah/ewok.h"
  #include "lockfile.h"
  #include "color.h"
  #include "commit.h"
  #include "blob.h"
  #include "tag.h"
  #include "diff.h"
  #include "diffcore.h"
  #include "revision.h"
  #include "log-tree.h"
  #include "builtin.h"
  #include "submodule.h"
  #include "oid-array.h"
  
  #define DIFF_NO_INDEX_EXPLICIT 1
  #define DIFF_NO_INDEX_IMPLICIT 2
  
  static const char builtin_diff_usage[] =
  "git diff [<options>] [<commit>] [--] [<path>...]\n"
  "   or: git diff [<options>] --cached [<commit>] [--] [<path>...]\n"
  "   or: git diff [<options>] <commit> [--merge-base] [<commit>...] <commit> [--] [<path>...]\n"
  "   or: git diff [<options>] <commit>...<commit>] [--] [<path>...]\n"
  "   or: git diff [<options>] <blob> <blob>]\n"
  "   or: git diff [<options>] --no-index [--] <path> <path>]\n"
  COMMON_DIFF_OPTIONS_HELP;
  
  static const char *blob_path(struct object_array_entry *entry)
  {
  	return entry->path ? entry->path : entry->name;
  }
  
  static void stuff_change(struct diff_options *opt,
  			 unsigned old_mode, unsigned new_mode,
  			 const struct object_id *old_oid,
  			 const struct object_id *new_oid,
  			 int old_oid_valid,
  			 int new_oid_valid,
  			 const char *old_path,
  			 const char *new_path)
  {
  	struct diff_filespec *one, *two;
  
  	if (!is_null_oid(old_oid) && !is_null_oid(new_oid) &&
  	    oideq(old_oid, new_oid) && (old_mode == new_mode))
  		return;
  
  	if (opt->flags.reverse_diff) {
  		SWAP(old_mode, new_mode);
  		SWAP(old_oid, new_oid);
  		SWAP(old_path, new_path);
  	}
  
  	if (opt->prefix &&
  	    (strncmp(old_path, opt->prefix, opt->prefix_length) ||
  	     strncmp(new_path, opt->prefix, opt->prefix_length)))
  		return;
  
  	one = alloc_filespec(old_path);
  	two = alloc_filespec(new_path);
  	fill_filespec(one, old_oid, old_oid_valid, old_mode);
  	fill_filespec(two, new_oid, new_oid_valid, new_mode);
  
  	diff_queue(&diff_queued_diff, one, two);
  }
  
  static int builtin_diff_b_f(struct rev_info *revs,
  			    int argc, const char **argv,
  			    struct object_array_entry **blob)
  {
  	/* Blob vs file in the working tree*/
  	struct stat st;
  	const char *path;
  
  	if (argc > 1)
  		usage(builtin_diff_usage);
  
  	GUARD_PATHSPEC(&revs->prune_data, PATHSPEC_FROMTOP | PATHSPEC_LITERAL);
  	path = revs->prune_data.items[0].match;
  
  	if (lstat(path, &st))
  		die_errno(_("failed to stat '%s'"), path);
  	if (!(S_ISREG(st.st_mode) || S_ISLNK(st.st_mode)))
  		die(_("'%s': not a regular file or symlink"), path);
  
  	diff_set_mnemonic_prefix(&revs->diffopt, "o/", "w/");
  
  	if (blob[0]->mode == S_IFINVALID)
  		blob[0]->mode = canon_mode(st.st_mode);
  
  	stuff_change(&revs->diffopt,
  		     blob[0]->mode, canon_mode(st.st_mode),
  		     &blob[0]->item->oid, &null_oid,
  		     1, 0,
  		     blob[0]->path ? blob[0]->path : path,
  		     path);
  	diffcore_std(&revs->diffopt);
  	diff_flush(&revs->diffopt);
  	return 0;
  }
  
  static int builtin_diff_blobs(struct rev_info *revs,
  			      int argc, const char **argv,
  			      struct object_array_entry **blob)
  {
  	const unsigned mode = canon_mode(S_IFREG | 0644);
  
  	if (argc > 1)
  		usage(builtin_diff_usage);
  
  	if (blob[0]->mode == S_IFINVALID)
  		blob[0]->mode = mode;
  
  	if (blob[1]->mode == S_IFINVALID)
  		blob[1]->mode = mode;
  
  	stuff_change(&revs->diffopt,
  		     blob[0]->mode, blob[1]->mode,
  		     &blob[0]->item->oid, &blob[1]->item->oid,
  		     1, 1,
  		     blob_path(blob[0]), blob_path(blob[1]));
  	diffcore_std(&revs->diffopt);
  	diff_flush(&revs->diffopt);
  	return 0;
  }
  
  static int builtin_diff_index(struct rev_info *revs,
  			      int argc, const char **argv)
  {
  	unsigned int option = 0;
  	while (1 < argc) {
  		const char *arg = argv[1];
  		if (!strcmp(arg, "--cached") || !strcmp(arg, "--staged"))
  			option |= DIFF_INDEX_CACHED;
  		else if (!strcmp(arg, "--merge-base"))
  			option |= DIFF_INDEX_MERGE_BASE;
  		else
  			usage(builtin_diff_usage);
  		argv++; argc--;
  	}
  	/*
  	 * Make sure there is one revision (i.e. pending object),
  	 * and there is no revision filtering parameters.
  	 */
  	if (revs->pending.nr != 1 ||
  	    revs->max_count != -1 || revs->min_age != -1 ||
  	    revs->max_age != -1)
  		usage(builtin_diff_usage);
  	if (!(option & DIFF_INDEX_CACHED)) {
  		setup_work_tree();
  		if (read_cache_preload(&revs->diffopt.pathspec) < 0) {
  			perror("read_cache_preload");
  			return -1;
  		}
  	} else if (read_cache() < 0) {
  		perror("read_cache");
  		return -1;
  	}
  	return run_diff_index(revs, option);
  }
  
  static int builtin_diff_tree(struct rev_info *revs,
  			     int argc, const char **argv,
  			     struct object_array_entry *ent0,
  			     struct object_array_entry *ent1)
  {
  	const struct object_id *(oid[2]);
  	struct object_id mb_oid;
  	int merge_base = 0;
  
  	while (1 < argc) {
  		const char *arg = argv[1];
  		if (!strcmp(arg, "--merge-base"))
  			merge_base = 1;
  		else
  			usage(builtin_diff_usage);
  		argv++; argc--;
  	}
  
  	if (merge_base) {
  		diff_get_merge_base(revs, &mb_oid);
  		oid[0] = &mb_oid;
  		oid[1] = &revs->pending.objects[1].item->oid;
  	} else {
  		int swap = 0;
  
  		/*
  		 * We saw two trees, ent0 and ent1.  If ent1 is uninteresting,
  		 * swap them.
  		 */
  		if (ent1->item->flags & UNINTERESTING)
  			swap = 1;
  		oid[swap] = &ent0->item->oid;
  		oid[1 - swap] = &ent1->item->oid;
  	}
  	diff_tree_oid(oid[0], oid[1], "", &revs->diffopt);
  	log_tree_diff_flush(revs);
  	return 0;
  }
  
  static int builtin_diff_combined(struct rev_info *revs,
  				 int argc, const char **argv,
  				 struct object_array_entry *ent,
  				 int ents)
  {
  	struct oid_array parents = OID_ARRAY_INIT;
  	int i;
  
  	if (argc > 1)
  		usage(builtin_diff_usage);
  
  	if (!revs->dense_combined_merges && !revs->combine_merges)
  		revs->dense_combined_merges = revs->combine_merges = 1;
  	for (i = 1; i < ents; i++)
  		oid_array_append(&parents, &ent[i].item->oid);
  	diff_tree_combined(&ent[0].item->oid, &parents, revs);
  	oid_array_clear(&parents);
  	return 0;
  }
  
  static void refresh_index_quietly(void)
  {
  	struct lock_file lock_file = LOCK_INIT;
  	int fd;
  
  	fd = hold_locked_index(&lock_file, 0);
  	if (fd < 0)
  		return;
  	discard_cache();
  	read_cache();
  	refresh_cache(REFRESH_QUIET|REFRESH_UNMERGED);
  	repo_update_index_if_able(the_repository, &lock_file);
  }
  
  static int builtin_diff_files(struct rev_info *revs, int argc, const char **argv)
  {
  	unsigned int options = 0;
  
  	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], "-q"))
  			options |= DIFF_SILENT_ON_REMOVED;
  		else if (!strcmp(argv[1], "-h"))
  			usage(builtin_diff_usage);
  		else
  			return error(_("invalid option: %s"), argv[1]);
  		argv++; argc--;
  	}
  
  	/*
  	 * "diff --base" should not combine merges because it was not
  	 * asked to.  "diff -c" should not densify (if the user wants
  	 * dense one, --cc can be explicitly asked for, or just rely
  	 * on the default).
  	 */
  	if (revs->max_count == -1 && !revs->combine_merges &&
  	    (revs->diffopt.output_format & DIFF_FORMAT_PATCH))
  		revs->combine_merges = revs->dense_combined_merges = 1;
  
  	setup_work_tree();
  	if (read_cache_preload(&revs->diffopt.pathspec) < 0) {
  		perror("read_cache_preload");
  		return -1;
  	}
  	return run_diff_files(revs, options);
  }
  
  struct symdiff {
  	struct bitmap *skip;
  	int warn;
  	const char *base, *left, *right;
  };
  
  /*
   * Check for symmetric-difference arguments, and if present, arrange
   * everything we need to know to handle them correctly.  As a bonus,
   * weed out all bogus range-based revision specifications, e.g.,
   * "git diff A..B C..D" or "git diff A..B C" get rejected.
   *
   * For an actual symmetric diff, *symdiff is set this way:
   *
   *  - its skip is non-NULL and marks *all* rev->pending.objects[i]
   *    indices that the caller should ignore (extra merge bases, of
   *    which there might be many, and A in A...B).  Note that the
   *    chosen merge base and right side are NOT marked.
   *  - warn is set if there are multiple merge bases.
   *  - base, left, and right point to the names to use in a
   *    warning about multiple merge bases.
   *
   * If there is no symmetric diff argument, sym->skip is NULL and
   * sym->warn is cleared.  The remaining fields are not set.
   */
  static void symdiff_prepare(struct rev_info *rev, struct symdiff *sym)
  {
  	int i, is_symdiff = 0, basecount = 0, othercount = 0;
  	int lpos = -1, rpos = -1, basepos = -1;
  	struct bitmap *map = NULL;
  
  	/*
  	 * Use the whence fields to find merge bases and left and
  	 * right parts of symmetric difference, so that we do not
  	 * depend on the order that revisions are parsed.  If there
  	 * are any revs that aren't from these sources, we have a
  	 * "git diff C A...B" or "git diff A...B C" case.  Or we
  	 * could even get "git diff A...B C...E", for instance.
  	 *
  	 * If we don't have just one merge base, we pick one
  	 * at random.
  	 *
  	 * NB: REV_CMD_LEFT, REV_CMD_RIGHT are also used for A..B,
  	 * so we must check for SYMMETRIC_LEFT too.  The two arrays
  	 * rev->pending.objects and rev->cmdline.rev are parallel.
  	 */
  	for (i = 0; i < rev->cmdline.nr; i++) {
  		struct object *obj = rev->pending.objects[i].item;
  		switch (rev->cmdline.rev[i].whence) {
  		case REV_CMD_MERGE_BASE:
  			if (basepos < 0)
  				basepos = i;
  			basecount++;
  			break;		/* do mark all bases */
  		case REV_CMD_LEFT:
  			if (lpos >= 0)
  				usage(builtin_diff_usage);
  			lpos = i;
  			if (obj->flags & SYMMETRIC_LEFT) {
  				is_symdiff = 1;
  				break;	/* do mark A */
  			}
  			continue;
  		case REV_CMD_RIGHT:
  			if (rpos >= 0)
  				usage(builtin_diff_usage);
  			rpos = i;
  			continue;	/* don't mark B */
  		case REV_CMD_PARENTS_ONLY:
  		case REV_CMD_REF:
  		case REV_CMD_REV:
  			othercount++;
  			continue;
  		}
  		if (map == NULL)
  			map = bitmap_new();
  		bitmap_set(map, i);
  	}
  
  	/*
  	 * Forbid any additional revs for both A...B and A..B.
  	 */
  	if (lpos >= 0 && othercount > 0)
  		usage(builtin_diff_usage);
  
  	if (!is_symdiff) {
  		bitmap_free(map);
  		sym->warn = 0;
  		sym->skip = NULL;
  		return;
  	}
  
  	sym->left = rev->pending.objects[lpos].name;
  	sym->right = rev->pending.objects[rpos].name;
  	if (basecount == 0)
  		die(_("%s...%s: no merge base"), sym->left, sym->right);
  	sym->base = rev->pending.objects[basepos].name;
  	bitmap_unset(map, basepos);	/* unmark the base we want */
  	sym->warn = basecount > 1;
  	sym->skip = map;
  }
  
  int cmd_diff(int argc, const char **argv, const char *prefix)
  {
  	int i;
  	struct rev_info rev;
  	struct object_array ent = OBJECT_ARRAY_INIT;
  	int blobs = 0, paths = 0;
  	struct object_array_entry *blob[2];
  	int nongit = 0, no_index = 0;
  	int result = 0;
  	struct symdiff sdiff;
  
  	/*
  	 * We could get N tree-ish in the rev.pending_objects list.
  	 * Also there could be M blobs there, and P pathspecs. --cached may
  	 * also be present.
  	 *
  	 * N=0, M=0:
  	 *      cache vs files (diff-files)
  	 *
  	 * N=0, M=0, --cached:
  	 *      HEAD vs cache (diff-index --cached)
  	 *
  	 * N=0, M=2:
  	 *      compare two random blobs.  P must be zero.
  	 *
  	 * N=0, M=1, P=1:
  	 *      compare a blob with a working tree file.
  	 *
  	 * N=1, M=0:
  	 *      tree vs files (diff-index)
  	 *
  	 * N=1, M=0, --cached:
  	 *      tree vs cache (diff-index --cached)
  	 *
  	 * N=2, M=0:
  	 *      tree vs tree (diff-tree)
  	 *
  	 * N=0, M=0, P=2:
  	 *      compare two filesystem entities (aka --no-index).
  	 *
  	 * Other cases are errors.
  	 */
  
  	/* Were we asked to do --no-index explicitly? */
  	for (i = 1; i < argc; i++) {
  		if (!strcmp(argv[i], "--")) {
  			i++;
  			break;
  		}
  		if (!strcmp(argv[i], "--no-index"))
  			no_index = DIFF_NO_INDEX_EXPLICIT;
  		if (argv[i][0] != '-')
  			break;
  	}
  
  	prefix = setup_git_directory_gently(&nongit);
  
  	if (!no_index) {
  		/*
  		 * Treat git diff with at least one path outside of the
  		 * repo the same as if the command would have been executed
  		 * outside of a git repository.  In this case it behaves
  		 * the same way as "git diff --no-index <a> <b>", which acts
  		 * as a colourful "diff" replacement.
  		 */
  		if (nongit || ((argc == i + 2) &&
  			       (!path_inside_repo(prefix, argv[i]) ||
  				!path_inside_repo(prefix, argv[i + 1]))))
  			no_index = DIFF_NO_INDEX_IMPLICIT;
  	}
  
  	init_diff_ui_defaults();
  	git_config(git_diff_ui_config, NULL);
  	precompose_argv(argc, argv);
  
  	repo_init_revisions(the_repository, &rev, prefix);
  
  	/* Set up defaults that will apply to both no-index and regular diffs. */
  	rev.diffopt.stat_width = -1;
  	rev.diffopt.stat_graph_width = -1;
  	rev.diffopt.flags.allow_external = 1;
  	rev.diffopt.flags.allow_textconv = 1;
  
  	/* If this is a no-index diff, just run it and exit there. */
  	if (no_index)
  		exit(diff_no_index(&rev, no_index == DIFF_NO_INDEX_IMPLICIT,
  				   argc, argv));
  
  
  	/*
  	 * Otherwise, we are doing the usual "git" diff; set up any
  	 * further defaults that apply to regular diffs.
  	 */
  	rev.diffopt.skip_stat_unmatch = !!diff_auto_refresh_index;
  
  	/*
  	 * Default to intent-to-add entries invisible in the
  	 * index. This makes them show up as new files in diff-files
  	 * and not at all in diff-cached.
  	 */
  	rev.diffopt.ita_invisible_in_index = 1;
  
  	if (nongit)
  		die(_("Not a git repository"));
  	argc = setup_revisions(argc, argv, &rev, NULL);
  	if (!rev.diffopt.output_format) {
  		rev.diffopt.output_format = DIFF_FORMAT_PATCH;
  		diff_setup_done(&rev.diffopt);
  	}
  
  	rev.diffopt.flags.recursive = 1;
  
  	setup_diff_pager(&rev.diffopt);
  
  	/*
  	 * Do we have --cached and not have a pending object, then
  	 * default to HEAD by hand.  Eek.
  	 */
  	if (!rev.pending.nr) {
  		int i;
  		for (i = 1; i < argc; i++) {
  			const char *arg = argv[i];
  			if (!strcmp(arg, "--"))
  				break;
  			else if (!strcmp(arg, "--cached") ||
  				 !strcmp(arg, "--staged")) {
  				add_head_to_pending(&rev);
  				if (!rev.pending.nr) {
  					struct tree *tree;
  					tree = lookup_tree(the_repository,
  							   the_repository->hash_algo->empty_tree);
  					add_pending_object(&rev, &tree->object, "HEAD");
  				}
  				break;
  			}
  		}
  	}
  
  	symdiff_prepare(&rev, &sdiff);
  	for (i = 0; i < rev.pending.nr; i++) {
  		struct object_array_entry *entry = &rev.pending.objects[i];
  		struct object *obj = entry->item;
  		const char *name = entry->name;
  		int flags = (obj->flags & UNINTERESTING);
  		if (!obj->parsed)
  			obj = parse_object(the_repository, &obj->oid);
  		obj = deref_tag(the_repository, obj, NULL, 0);
  		if (!obj)
  			die(_("invalid object '%s' given."), name);
  		if (obj->type == OBJ_COMMIT)
  			obj = &get_commit_tree(((struct commit *)obj))->object;
  
  		if (obj->type == OBJ_TREE) {
  			if (sdiff.skip && bitmap_get(sdiff.skip, i))
  				continue;
  			obj->flags |= flags;
  			add_object_array(obj, name, &ent);
  		} else if (obj->type == OBJ_BLOB) {
  			if (2 <= blobs)
  				die(_("more than two blobs given: '%s'"), name);
  			blob[blobs] = entry;
  			blobs++;
  
  		} else {
  			die(_("unhandled object '%s' given."), name);
  		}
  	}
  	if (rev.prune_data.nr)
  		paths += rev.prune_data.nr;
  
  	/*
  	 * Now, do the arguments look reasonable?
  	 */
  	if (!ent.nr) {
  		switch (blobs) {
  		case 0:
  			result = builtin_diff_files(&rev, argc, argv);
  			break;
  		case 1:
  			if (paths != 1)
  				usage(builtin_diff_usage);
  			result = builtin_diff_b_f(&rev, argc, argv, blob);
  			break;
  		case 2:
  			if (paths)
  				usage(builtin_diff_usage);
  			result = builtin_diff_blobs(&rev, argc, argv, blob);
  			break;
  		default:
  			usage(builtin_diff_usage);
  		}
  	}
  	else if (blobs)
  		usage(builtin_diff_usage);
  	else if (ent.nr == 1)
  		result = builtin_diff_index(&rev, argc, argv);
  	else if (ent.nr == 2) {
  		if (sdiff.warn)
  			warning(_("%s...%s: multiple merge bases, using %s"),
  				sdiff.left, sdiff.right, sdiff.base);
  		result = builtin_diff_tree(&rev, argc, argv,
  					   &ent.objects[0], &ent.objects[1]);
  	} else
  		result = builtin_diff_combined(&rev, argc, argv,
  					       ent.objects, ent.nr);
  	result = diff_result_code(&rev.diffopt, result);
  	if (1 < rev.diffopt.skip_stat_unmatch)
  		refresh_index_quietly();
  	UNLEAK(rev);
  	UNLEAK(ent);
  	UNLEAK(blob);
  	return result;
  }
  