diff-files: -c and --cc options.

This ports the "combined diff" to diff-files so that differences
to the working tree files since stage 2 and stage 3 are shown
the same way as combined diff output from diff-tree for the
merge commit would be shown if the current working tree files
are committed.

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

3 files changed, 99 insertions, 23 deletions

diff --git a/combine-diff.c b/combine-diff.c
index df52fa20ec..243f96775a 100644
--- a/combine-diff.c
+++ b/combine-diff.c
@@ -4,14 +4,6 @@
 #include "diffcore.h"
 #include "quote.h"
 
-struct path_list {
-	struct path_list *next;
-	int len;
-	char *path;
-	unsigned char sha1[20];
-	unsigned char parent_sha1[FLEX_ARRAY][20];
-};
-
 static int uninteresting(struct diff_filepair *p)
 {
 	if (diff_unmodified_pair(p))
@@ -21,15 +13,14 @@ static int uninteresting(struct diff_filepair *p)
 	return 0;
 }
 
-static struct path_list *intersect_paths(struct path_list *curr,
-					 int n, int num_parent)
+static struct combine_diff_path *intersect_paths(struct combine_diff_path *curr, int n, int num_parent)
 {
 	struct diff_queue_struct *q = &diff_queued_diff;
-	struct path_list *p;
+	struct combine_diff_path *p;
 	int i;
 
 	if (!n) {
-		struct path_list *list = NULL, **tail = &list;
+		struct combine_diff_path *list = NULL, **tail = &list;
 		for (i = 0; i < q->nr; i++) {
 			int len;
 			const char *path;
@@ -532,18 +523,52 @@ static void dump_sline(struct sline *sline, int cnt, int num_parent)
 	}
 }
 
-static int show_combined_diff(struct path_list *elem, int num_parent,
-			      int dense, const char *header, int show_empty)
+int show_combined_diff(struct combine_diff_path *elem, int num_parent,
+		       int dense, const char *header, int show_empty)
 {
 	unsigned long size, cnt, lno;
 	char *result, *cp, *ep;
 	struct sline *sline; /* survived lines */
 	int i, show_hunks, shown_header = 0;
-	char ourtmp[TMPPATHLEN];
+	char ourtmp_buf[TMPPATHLEN];
+	char *ourtmp = ourtmp_buf;
 
 	/* Read the result of merge first */
-	result = grab_blob(elem->sha1, &size);
-	write_to_temp_file(ourtmp, result, size);
+	if (memcmp(elem->sha1, null_sha1, 20)) {
+		result = grab_blob(elem->sha1, &size);
+		write_to_temp_file(ourtmp, result, size);
+	}
+	else {
+		struct stat st;
+		int fd;
+		ourtmp = elem->path;
+		if (0 <= (fd = open(ourtmp, O_RDONLY)) &&
+		    !fstat(fd, &st)) {
+			int len = st.st_size;
+			int cnt = 0;
+
+			size = len;
+			result = xmalloc(len + 1);
+			while (cnt < len) {
+				int done = xread(fd, result+cnt, len-cnt);
+				if (done == 0)
+					break;
+				if (done < 0)
+					die("read error '%s'", ourtmp);
+				cnt += done;
+			}
+			result[len] = 0;
+		}
+		else {
+			/* deleted file */
+			size = 0;
+			result = xmalloc(1);
+			result[0] = 0;
+			ourtmp = "/dev/null";
+		}
+		if (0 <= fd)
+			close(fd);
+	}
 
 	for (cnt = 0, cp = result; cp - result < size; cp++) {
 		if (*cp == '\n')
@@ -589,7 +614,8 @@ static int show_combined_diff(struct path_list *elem, int num_parent,
 		putchar('\n');
 		dump_sline(sline, cnt, num_parent);
 	}
-	unlink(ourtmp);
+	if (ourtmp == ourtmp_buf)
+		unlink(ourtmp);
 	free(result);
 
 	for (i = 0; i < cnt; i++) {
@@ -613,7 +639,7 @@ int diff_tree_combined_merge(const unsigned char *sha1,
 	struct commit *commit = lookup_commit(sha1);
 	struct diff_options diffopts;
 	struct commit_list *parents;
-	struct path_list *p, *paths = NULL;
+	struct combine_diff_path *p, *paths = NULL;
 	int num_parent, i, num_paths;
 
 	diff_setup(&diffopts);
@@ -654,7 +680,7 @@ int diff_tree_combined_merge(const unsigned char *sha1,
 
 	/* Clean things up */
 	while (paths) {
-		struct path_list *tmp = paths;
+		struct combine_diff_path *tmp = paths;
 		paths = paths->next;
 		free(tmp);
 	}
diff --git a/diff-files.c b/diff-files.c
index 6c0696c34f..4a30c56f84 100644
--- a/diff-files.c
+++ b/diff-files.c
@@ -7,12 +7,14 @@
 #include "diff.h"
 
 static const char diff_files_usage[] =
-"git-diff-files [-q] [-0/-1/2/3] [<common diff options>] [<path>...]"
+"git-diff-files [-q] [-0/-1/2/3 |-c|--cc] [<common diff options>] [<path>...]"
 COMMON_DIFF_OPTIONS_HELP;
 
 static struct diff_options diff_options;
 static int silent = 0;
 static int diff_unmerged_stage = 2;
+static int combine_merges = 0;
+static int dense_combined_merges = 0;
 
 static void show_unmerge(const char *path)
 {
@@ -66,6 +68,10 @@ int main(int argc, const char **argv)
 			; /* no-op */
 		else if (!strcmp(argv[1], "-s"))
 			; /* no-op */
+		else if (!strcmp(argv[1], "-c"))
+			combine_merges = 1;
+		else if (!strcmp(argv[1], "--cc"))
+			dense_combined_merges = combine_merges = 1;
 		else {
 			int diff_opt_cnt;
 			diff_opt_cnt = diff_opt_parse(&diff_options,
@@ -82,6 +88,9 @@ int main(int argc, const char **argv)
 		}
 		argv++; argc--;
 	}
+	if (combine_merges) {
+		diff_options.output_format = DIFF_FORMAT_PATCH;
+	}
 
 	/* Find the directory, and set up the pathspec */
 	pathspec = get_pathspec(prefix, argv + 1);
@@ -108,14 +117,35 @@ int main(int argc, const char **argv)
 			continue;
 
 		if (ce_stage(ce)) {
-			show_unmerge(ce->name);
+			struct {
+				struct combine_diff_path p;
+				unsigned char fill[4][20];
+			} combine;
+
+			combine.p.next = NULL;
+			combine.p.len = ce_namelen(ce);
+			combine.p.path = xmalloc(combine.p.len + 1);
+			memcpy(combine.p.path, ce->name, combine.p.len);
+			combine.p.path[combine.p.len] = 0;
+			memset(combine.p.sha1, 0, 100);
+
 			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)
+					memcpy(combine.p.parent_sha1[stage-2],
+					       nce->sha1, 20);
+
 				/* diff against the proper unmerged stage */
-				if (ce_stage(nce) == diff_unmerged_stage)
+				if (stage == diff_unmerged_stage)
 					ce = nce;
 				i++;
 			}
@@ -123,10 +153,19 @@ int main(int argc, const char **argv)
 			 * Compensate for loop update
 			 */
 			i--;
+
+			if (combine_merges) {
+				show_combined_diff(&combine.p, 2,
+						   dense_combined_merges,
+						   NULL, 0);
+				continue;
+			}
+
 			/*
 			 * Show the diff for the 'ce' if we found the one
 			 * from the desired stage.
 			 */
+			show_unmerge(ce->name);
 			if (ce_stage(ce) != diff_unmerged_stage)
 				continue;
 		}
diff --git a/diff.h b/diff.h
index ab0d47b982..539bd2f5ce 100644
--- a/diff.h
+++ b/diff.h
@@ -56,6 +56,17 @@ extern int diff_tree(struct tree_desc *t1, struct tree_desc *t2,
 extern int diff_tree_sha1(const unsigned char *old, const unsigned char *new,
 			  const char *base, struct diff_options *opt);
 
+struct combine_diff_path {
+	struct combine_diff_path *next;
+	int len;
+	char *path;
+	unsigned char sha1[20];
+	unsigned char parent_sha1[FLEX_ARRAY][20];
+};
+
+int show_combined_diff(struct combine_diff_path *elem, int num_parent,
+		       int dense, const char *header, int show_empty);
+
 extern int diff_tree_combined_merge(const unsigned char *sha1, const char *, int, int);
 
 extern void diff_addremove(struct diff_options *,