Subject: [PATCH v7 26/31] merge-recursive: avoid clobbering untracked files with directory renames

From: Elijah Newren <[email-masked]>
Date: Tue, 30 Jan 2018 15:25:28 -0800

Signed-off-by: Elijah Newren <[email-masked]>
---
 merge-recursive.c                   | 42 +++++++++++++++++++++++++++++++++++--
 t/t6043-merge-rename-directories.sh |  6 +++---
 2 files changed, 43 insertions(+), 5 deletions(-)

diff --git a/merge-recursive.c b/merge-recursive.c
index 7c78dc2dc1..39e161e094 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -1147,6 +1147,26 @@ static int conflict_rename_dir(struct merge_options *o,
 {
 	const struct diff_filespec *dest = pair->two;
 
+	if (!o->call_depth && would_lose_untracked(dest->path)) {
+		char *alt_path = unique_path(o, dest->path, rename_branch);
+
+		output(o, 1, _("Error: Refusing to lose untracked file at %s; "
+			       "writing to %s instead."),
+		       dest->path, alt_path);
+		/*
+		 * Write the file in worktree at alt_path, but not in the
+		 * index.  Instead, write to dest->path for the index but
+		 * only at the higher appropriate stage.
+		 */
+		if (update_file(o, 0, &dest->oid, dest->mode, alt_path))
+			return -1;
+		free(alt_path);
+		return update_stages(o, dest->path, NULL,
+				     rename_branch == o->branch1 ? dest : NULL,
+				     rename_branch == o->branch1 ? NULL : dest);
+	}
+
+	/* Update dest->path both in index and in worktree */
 	if (update_file(o, 1, &dest->oid, dest->mode, dest->path))
 		return -1;
 	return 0;
@@ -1165,7 +1185,8 @@ static int handle_change_delete(struct merge_options *o,
 	const char *update_path = path;
 	int ret = 0;
 
-	if (dir_in_way(path, !o->call_depth, 0)) {
+	if (dir_in_way(path, !o->call_depth, 0) ||
+	    (!o->call_depth && would_lose_untracked(path))) {
 		update_path = alt_path = unique_path(o, path, change_branch);
 	}
 
@@ -1291,6 +1312,12 @@ static int handle_file(struct merge_options *o,
 			dst_name = unique_path(o, rename->path, cur_branch);
 			output(o, 1, _("%s is a directory in %s adding as %s instead"),
 			       rename->path, other_branch, dst_name);
+		} else if (!o->call_depth &&
+			   would_lose_untracked(rename->path)) {
+			dst_name = unique_path(o, rename->path, cur_branch);
+			output(o, 1, _("Refusing to lose untracked file at %s; "
+				       "adding as %s instead"),
+			       rename->path, dst_name);
 		}
 	}
 	if ((ret = update_file(o, 0, &rename->oid, rename->mode, dst_name)))
@@ -1416,7 +1443,18 @@ static int conflict_rename_rename_2to1(struct merge_options *o,
 		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);
-		remove_file(o, 0, path, 0);
+		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,
diff --git a/t/t6043-merge-rename-directories.sh b/t/t6043-merge-rename-directories.sh
index b6207763cf..abb5b20f6b 100755
--- a/t/t6043-merge-rename-directories.sh
+++ b/t/t6043-merge-rename-directories.sh
@@ -2984,7 +2984,7 @@ test_expect_success '10b-setup: Overwrite untracked with dir rename + delete' '
 	)
 '
 
-test_expect_failure '10b-check: Overwrite untracked with dir rename + delete' '
+test_expect_success '10b-check: Overwrite untracked with dir rename + delete' '
 	(
 		cd 10b &&
 
@@ -3062,7 +3062,7 @@ test_expect_success '10c-setup: Overwrite untracked with dir rename/rename(1to2)
 	)
 '
 
-test_expect_failure '10c-check: Overwrite untracked with dir rename/rename(1to2)' '
+test_expect_success '10c-check: Overwrite untracked with dir rename/rename(1to2)' '
 	(
 		cd 10c &&
 
@@ -3137,7 +3137,7 @@ test_expect_success '10d-setup: Delete untracked with dir rename/rename(2to1)' '
 	)
 '
 
-test_expect_failure '10d-check: Delete untracked with dir rename/rename(2to1)' '
+test_expect_success '10d-check: Delete untracked with dir rename/rename(2to1)' '
 	(
 		cd 10d &&
 
-- 
2.16.1.106.gf69932adfe