Libify diff-index.

The second installment to libify diff brothers.  The pathname
arguments are checked more strictly than before because we now
use the revision.c::setup_revisions() infrastructure.

Signed-off-by: Junio C Hamano <junkio@cox.net>

diff-lib.c

@@ -131,3 +131,206 @@ int run_diff_files(struct rev_info *revs, int silent_on_removed)
 	return 0;
 }
 
+/*
+ * diff-index
+ */
+
+/* A file entry went away or appeared */
+static void diff_index_show_file(struct rev_info *revs,
+				 const char *prefix,
+				 struct cache_entry *ce,
+				 unsigned char *sha1, unsigned int mode)
+{
+	diff_addremove(&revs->diffopt, prefix[0], ntohl(mode),
+		       sha1, ce->name, NULL);
+}
+
+static int get_stat_data(struct cache_entry *ce,
+			 unsigned char **sha1p,
+			 unsigned int *modep,
+			 int cached, int match_missing)
+{
+	unsigned char *sha1 = ce->sha1;
+	unsigned int mode = ce->ce_mode;
+
+	if (!cached) {
+		static unsigned char no_sha1[20];
+		int changed;
+		struct stat st;
+		if (lstat(ce->name, &st) < 0) {
+			if (errno == ENOENT && match_missing) {
+				*sha1p = sha1;
+				*modep = mode;
+				return 0;
+			}
+			return -1;
+		}
+		changed = ce_match_stat(ce, &st, 0);
+		if (changed) {
+			mode = create_ce_mode(st.st_mode);
+			if (!trust_executable_bit && S_ISREG(st.st_mode))
+				mode = ce->ce_mode;
+			sha1 = no_sha1;
+		}
+	}
+
+	*sha1p = sha1;
+	*modep = mode;
+	return 0;
+}
+
+static void show_new_file(struct rev_info *revs,
+			  struct cache_entry *new,
+			  int cached, int match_missing)
+{
+	unsigned char *sha1;
+	unsigned int mode;
+
+	/* New file in the index: it might actually be different in
+	 * the working copy.
+	 */
+	if (get_stat_data(new, &sha1, &mode, cached, match_missing) < 0)
+		return;
+
+	diff_index_show_file(revs, "+", new, sha1, mode);
+}
+
+static int show_modified(struct rev_info *revs,
+			 struct cache_entry *old,
+			 struct cache_entry *new,
+			 int report_missing,
+			 int cached, int match_missing)
+{
+	unsigned int mode, oldmode;
+	unsigned char *sha1;
+
+	if (get_stat_data(new, &sha1, &mode, cached, match_missing) < 0) {
+		if (report_missing)
+			diff_index_show_file(revs, "-", old,
+					     old->sha1, old->ce_mode);
+		return -1;
+	}
+
+	oldmode = old->ce_mode;
+	if (mode == oldmode && !memcmp(sha1, old->sha1, 20) &&
+	    !revs->diffopt.find_copies_harder)
+		return 0;
+
+	mode = ntohl(mode);
+	oldmode = ntohl(oldmode);
+
+	diff_change(&revs->diffopt, oldmode, mode,
+		    old->sha1, sha1, old->name, NULL);
+	return 0;
+}
+
+static int diff_cache(struct rev_info *revs,
+		      struct cache_entry **ac, int entries,
+		      const char **pathspec,
+		      int cached, int match_missing)
+{
+	while (entries) {
+		struct cache_entry *ce = *ac;
+		int same = (entries > 1) && ce_same_name(ce, ac[1]);
+
+		if (!ce_path_match(ce, pathspec))
+			goto skip_entry;
+
+		switch (ce_stage(ce)) {
+		case 0:
+			/* No stage 1 entry? That means it's a new file */
+			if (!same) {
+				show_new_file(revs, ce, cached, match_missing);
+				break;
+			}
+			/* Show difference between old and new */
+			show_modified(revs,ac[1], ce, 1,
+				      cached, match_missing);
+			break;
+		case 1:
+			/* No stage 3 (merge) entry?
+			 * That means it's been deleted.
+			 */
+			if (!same) {
+				diff_index_show_file(revs, "-", ce,
+						     ce->sha1, ce->ce_mode);
+				break;
+			}
+			/* We come here with ce pointing at stage 1
+			 * (original tree) and ac[1] pointing at stage
+			 * 3 (unmerged).  show-modified with
+			 * report-missing set to false does not say the
+			 * file is deleted but reports true if work
+			 * tree does not have it, in which case we
+			 * fall through to report the unmerged state.
+			 * Otherwise, we show the differences between
+			 * the original tree and the work tree.
+			 */
+			if (!cached &&
+			    !show_modified(revs, ce, ac[1], 0,
+					   cached, match_missing))
+				break;
+			/* fallthru */
+		case 3:
+			diff_unmerge(&revs->diffopt, ce->name);
+			break;
+
+		default:
+			die("impossible cache entry stage");
+		}
+
+skip_entry:
+		/*
+		 * Ignore all the different stages for this file,
+		 * we've handled the relevant cases now.
+		 */
+		do {
+			ac++;
+			entries--;
+		} while (entries && ce_same_name(ce, ac[0]));
+	}
+	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 |= htons(CE_STAGEMASK);
+	}
+}
+
+int run_diff_index(struct rev_info *revs, int cached, int match_missing)
+{
+	int ret;
+	struct object *ent;
+	struct tree *tree;
+	const char *tree_name;
+
+	if (read_cache() < 0) {
+		perror("read_cache");
+		return -1;
+	}
+	mark_merge_entries();
+
+	ent = revs->pending_objects->item;
+	tree_name = revs->pending_objects->name;
+	tree = parse_tree_indirect(ent->sha1);
+	if (!tree)
+		return error("bad tree object %s", tree_name);
+	if (read_tree(tree, 1, revs->prune_data))
+		return error("unable to read tree object %s", tree_name);
+	ret = diff_cache(revs, active_cache, active_nr, revs->prune_data,
+			 cached, match_missing);
+	diffcore_std(&revs->diffopt);
+	diff_flush(&revs->diffopt);
+	return ret;
+}