diff-index --cached --raw: show tree entry on the LHS for unmerged en…

…tries.

This updates the way diffcore represents an unmerged pair
somewhat.  It used to be that entries with mode=0 on both sides
were used to represent an unmerged pair, but now it has an
explicit flag.  This is to allow diff-index --cached to report
the entry from the tree when the path is unmerged in the index.

This is used in updating "git reset <tree> -- <path>" to restore
absense of the path in the index from the tree.

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

diff-lib.c

@@ -97,7 +97,7 @@ int run_diff_files(struct rev_info *revs, int silent_on_removed)
 			 * Show the diff for the 'ce' if we found the one
 			 * from the desired stage.
 			 */
-			diff_unmerge(&revs->diffopt, ce->name);
+			diff_unmerge(&revs->diffopt, ce->name, 0, null_sha1);
 			if (ce_stage(ce) != diff_unmerged_stage)
 				continue;
 		}
@@ -297,9 +297,12 @@ static int diff_cache(struct rev_info *revs,
 			    !show_modified(revs, ce, ac[1], 0,
 					   cached, match_missing))
 				break;
-			/* fallthru */
+			diff_unmerge(&revs->diffopt, ce->name,
+				     ntohl(ce->ce_mode), ce->sha1);
+			break;
 		case 3:
-			diff_unmerge(&revs->diffopt, ce->name);
+			diff_unmerge(&revs->diffopt, ce->name,
+				     0, null_sha1);
 			break;
 
 		default:

diff.c

@@ -2875,10 +2875,12 @@ void diff_change(struct diff_options *options,
 }
 
 void diff_unmerge(struct diff_options *options,
-		  const char *path)
+		  const char *path,
+		  unsigned mode, const unsigned char *sha1)
 {
 	struct diff_filespec *one, *two;
 	one = alloc_filespec(path);
 	two = alloc_filespec(path);
-	diff_queue(&diff_queued_diff, one, two);
+	fill_filespec(one, sha1, mode);
+	diff_queue(&diff_queued_diff, one, two)->is_unmerged = 1;
 }

diff.h

@@ -144,7 +144,9 @@ extern void diff_change(struct diff_options *,
 			const char *base, const char *path);
 
 extern void diff_unmerge(struct diff_options *,
-			 const char *path);
+			 const char *path,
+			 unsigned mode,
+			 const unsigned char *sha1);
 
 extern int diff_scoreopt_parse(const char *opt);
 

diffcore.h

@@ -54,9 +54,9 @@ struct diff_filepair {
 	unsigned source_stays : 1; /* all of R/C are copies */
 	unsigned broken_pair : 1;
 	unsigned renamed_pair : 1;
+	unsigned is_unmerged : 1;
 };
-#define DIFF_PAIR_UNMERGED(p) \
-	(!DIFF_FILE_VALID((p)->one) && !DIFF_FILE_VALID((p)->two))
+#define DIFF_PAIR_UNMERGED(p) ((p)->is_unmerged)
 
 #define DIFF_PAIR_RENAME(p) ((p)->renamed_pair)