merge-recursive: improve handling for rename/rename(2to1) conflicts

This makes the rename/rename(2to1) conflicts use the new
handle_file_collision() function.  Since that function was based
originally on the rename/rename(2to1) handling code, the main
differences here are in what was added.  In particular:

  * Instead of storing files at collide_path~HEAD and collide_path~MERGE,
    the files are two-way merged and recorded at collide_path.

  * Instead of recording the version of the renamed file that existed
    on the renamed side in the index (thus ignoring any changes that
    were made to the file on the side of history without the rename),
    we do a three-way content merge on the renamed path, then store
    that at either stage 2 or stage 3.

  * Note that since the content merge for each rename may have conflicts,
    and then we have to merge the two renamed files, we can end up with
    nested conflict markers.

Signed-off-by: Elijah Newren <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: newren

merge-recursive.c

@@ -696,27 +696,6 @@ static int update_stages(struct merge_options *opt, const char *path,
 	return 0;
 }
 
-static int update_stages_for_stage_data(struct merge_options *opt,
-					const char *path,
-					const struct stage_data *stage_data)
-{
-	struct diff_filespec o, a, b;
-
-	o.mode = stage_data->stages[1].mode;
-	oidcpy(&o.oid, &stage_data->stages[1].oid);
-
-	a.mode = stage_data->stages[2].mode;
-	oidcpy(&a.oid, &stage_data->stages[2].oid);
-
-	b.mode = stage_data->stages[3].mode;
-	oidcpy(&b.oid, &stage_data->stages[3].oid);
-
-	return update_stages(opt, path,
-			     is_null_oid(&o.oid) ? NULL : &o,
-			     is_null_oid(&a.oid) ? NULL : &a,
-			     is_null_oid(&b.oid) ? NULL : &b);
-}
-
 static void update_entry(struct stage_data *entry,
 			 struct diff_filespec *o,
 			 struct diff_filespec *a,
@@ -1870,89 +1849,29 @@ static int handle_rename_rename_2to1(struct merge_options *o,
 	char *path_side_2_desc;
 	struct merge_file_info mfi_c1;
 	struct merge_file_info mfi_c2;
-	int ret;
 
 	output(o, 1, _("CONFLICT (rename/rename): "
 	       "Rename %s->%s in %s. "
 	       "Rename %s->%s in %s"),
 	       a->path, c1->path, ci->branch1,
 	       b->path, c2->path, ci->branch2);
 
-	remove_file(o, 1, a->path, o->call_depth || would_lose_untracked(a->path));
-	remove_file(o, 1, b->path, o->call_depth || would_lose_untracked(b->path));
-
 	path_side_1_desc = xstrfmt("version of %s from %s", path, a->path);
 	path_side_2_desc = xstrfmt("version of %s from %s", path, b->path);
 	if (merge_mode_and_contents(o, a, c1, &ci->ren1_other, path_side_1_desc,
 				    o->branch1, o->branch2,
-				    o->call_depth * 2, &mfi_c1) ||
+				    1 + o->call_depth * 2, &mfi_c1) ||
 	    merge_mode_and_contents(o, b, &ci->ren2_other, c2, path_side_2_desc,
 				    o->branch1, o->branch2,
-				    o->call_depth * 2, &mfi_c2))
+				    1 + o->call_depth * 2, &mfi_c2))
 		return -1;
 	free(path_side_1_desc);
 	free(path_side_2_desc);
 
-	if (o->call_depth) {
-		/*
-		 * If mfi_c1.clean && mfi_c2.clean, then it might make
-		 * sense to do a two-way merge of those results.  But, I
-		 * think in all cases, it makes sense to have the virtual
-		 * merge base just undo the renames; they can be detected
-		 * again later for the non-recursive merge.
-		 */
-		remove_file(o, 0, path, 0);
-		ret = update_file(o, 0, &mfi_c1.oid, mfi_c1.mode, a->path);
-		if (!ret)
-			ret = update_file(o, 0, &mfi_c2.oid, mfi_c2.mode,
-					  b->path);
-	} else {
-		char *new_path1 = unique_path(o, path, ci->branch1);
-		char *new_path2 = unique_path(o, path, ci->branch2);
-		output(o, 1, _("Renaming %s to %s and %s to %s instead"),
-		       a->path, new_path1, b->path, new_path2);
-		if (was_dirty(o, path))
-			output(o, 1, _("Refusing to lose dirty file at %s"),
-			       path);
-		else if (would_lose_untracked(path))
-			/*
-			 * Only way we get here is if both renames were from
-			 * a directory rename AND user had an untracked file
-			 * at the location where both files end up after the
-			 * two directory renames.  See testcase 10d of t6043.
-			 */
-			output(o, 1, _("Refusing to lose untracked file at "
-				       "%s, even though it's in the way."),
-			       path);
-		else
-			remove_file(o, 0, path, 0);
-		ret = update_file(o, 0, &mfi_c1.oid, mfi_c1.mode, new_path1);
-		if (!ret)
-			ret = update_file(o, 0, &mfi_c2.oid, mfi_c2.mode,
-					  new_path2);
-		/*
-		 * unpack_trees() actually populates the index for us for
-		 * "normal" rename/rename(2to1) situtations so that the
-		 * correct entries are at the higher stages, which would
-		 * make the call below to update_stages_for_stage_data
-		 * unnecessary.  However, if either of the renames came
-		 * from a directory rename, then unpack_trees() will not
-		 * have gotten the right data loaded into the index, so we
-		 * need to do so now.  (While it'd be tempting to move this
-		 * call to update_stages_for_stage_data() to
-		 * apply_directory_rename_modifications(), that would break
-		 * our intermediate calls to would_lose_untracked() since
-		 * those rely on the current in-memory index.  See also the
-		 * big "NOTE" in update_stages()).
-		 */
-		if (update_stages_for_stage_data(o, path, ci->dst_entry1))
-			ret = -1;
-
-		free(new_path2);
-		free(new_path1);
-	}
-
-	return ret;
+	return handle_file_collision(o, path, a->path, b->path,
+				     ci->branch1, ci->branch2,
+				     &mfi_c1.oid, mfi_c1.mode,
+				     &mfi_c2.oid, mfi_c2.mode);
 }
 
 /*
@@ -3361,9 +3280,14 @@ static int process_entry(struct merge_options *o,
 				clean_merge = -1;
 			break;
 		case RENAME_TWO_FILES_TO_ONE:
-			clean_merge = 0;
-			if (handle_rename_rename_2to1(o, conflict_info))
-				clean_merge = -1;
+			/*
+			 * Probably unclean merge, but if the two renamed
+			 * files merge cleanly and the two resulting files
+			 * can then be two-way merged cleanly, I guess it's
+			 * a clean merge?
+			 */
+			clean_merge = handle_rename_rename_2to1(o,
+								conflict_info);
 			break;
 		default:
 			entry->processed = 0;

t/t6036-recursive-corner-cases.sh

@@ -64,15 +64,12 @@ test_expect_success 'merge simple rename+criss-cross with no modifications' '
 		git ls-files -u >out &&
 		test_line_count = 2 out &&
 		git ls-files -o >out &&
-		test_line_count = 3 out &&
+		test_line_count = 1 out &&
 
 		git rev-parse >expect       \
-			L2:three   R2:three \
 			L2:three   R2:three &&
 		git rev-parse   >actual     \
 			:2:three   :3:three &&
-		git hash-object >>actual    \
-			three~HEAD three~R2^0 &&
 		test_cmp expect actual
 	)
 '
@@ -140,15 +137,12 @@ test_expect_success 'merge criss-cross + rename merges with basic modification'
 		git ls-files -u >out &&
 		test_line_count = 2 out &&
 		git ls-files -o >out &&
-		test_line_count = 3 out &&
+		test_line_count = 1 out &&
 
 		git rev-parse >expect       \
-			L2:three   R2:three \
 			L2:three   R2:three &&
 		git rev-parse   >actual     \
 			:2:three   :3:three &&
-		git hash-object >>actual    \
-			three~HEAD three~R2^0 &&
 		test_cmp expect actual
 	)
 '
@@ -1512,7 +1506,7 @@ test_expect_success 'setup nested conflicts' '
 	)
 '
 
-test_expect_failure 'check nested conflicts' '
+test_expect_success 'check nested conflicts' '
 	(
 		cd nested_conflicts &&
 

t/t6042-merge-rename-corner-cases.sh

@@ -464,17 +464,28 @@ test_expect_success 'handle rename/rename (2to1) conflict correctly' '
 		git ls-files -u c >out &&
 		test_line_count = 2 out &&
 		git ls-files -o >out &&
-		test_line_count = 3 out &&
+		test_line_count = 1 out &&
 
 		test_path_is_missing a &&
 		test_path_is_missing b &&
-		test_path_is_file c~HEAD &&
-		test_path_is_file c~C^0 &&
 
-		git rev-parse >expect   \
-			C:a     B:b     &&
-		git hash-object >actual \
-			c~HEAD  c~C^0   &&
+		git rev-parse >expect  \
+			C:a     B:b    &&
+		git rev-parse >actual  \
+			:2:c    :3:c   &&
+		test_cmp expect actual &&
+
+		# Test that the two-way merge in new_a is as expected
+		git cat-file -p :2:c >>ours &&
+		git cat-file -p :3:c >>theirs &&
+		>empty &&
+		test_must_fail git merge-file \
+			-L "HEAD" \
+			-L "" \
+			-L "C^0" \
+			ours empty theirs &&
+		git hash-object c >actual &&
+		git hash-object ours >expect &&
 		test_cmp expect actual
 	)
 '
@@ -940,7 +951,6 @@ test_expect_failure 'mod6-check: chains of rename/rename(1to2) and rename/rename
 test_conflicts_with_adds_and_renames() {
 	sideL=$1
 	sideR=$2
-	expect=$3
 
 	# Setup:
 	#          L
@@ -1048,7 +1058,7 @@ test_conflicts_with_adds_and_renames() {
 		)
 	'
 
-	test_expect_$expect "check simple $sideL/$sideR conflict" '
+	test_expect_success "check simple $sideL/$sideR conflict" '
 		(
 			cd simple_${sideL}_${sideR} &&
 
@@ -1094,10 +1104,10 @@ test_conflicts_with_adds_and_renames() {
 	'
 }
 
-test_conflicts_with_adds_and_renames rename rename failure
-test_conflicts_with_adds_and_renames rename add    success
-test_conflicts_with_adds_and_renames add    rename success
-test_conflicts_with_adds_and_renames add    add    success
+test_conflicts_with_adds_and_renames rename rename
+test_conflicts_with_adds_and_renames rename add
+test_conflicts_with_adds_and_renames add    rename
+test_conflicts_with_adds_and_renames add    add
 
 # Setup:
 #          L
@@ -1168,7 +1178,7 @@ test_expect_success 'setup nested conflicts from rename/rename(2to1)' '
 	)
 '
 
-test_expect_failure 'check nested conflicts from rename/rename(2to1)' '
+test_expect_success 'check nested conflicts from rename/rename(2to1)' '
 	(
 		cd nested_conflicts_from_rename_rename &&