Re: [PATCH] modify/delete conflict resolution overwrites untracked file

Junio C Hamano [off-list ref] writes:

Clemens Buchacher [off-list ref] writes:

quoted

On Wed, Dec 10, 2008 at 09:12:59PM +0100, Clemens Buchacher wrote:

quoted

If a file was removed in HEAD, but modified in MERGE_HEAD, recursive merge
will result in a "CONFLICT (delete/modify)". If the (now untracked) file
already exists and was not added to the index, it is overwritten with the
conflict resolution contents.

The following patch fixes the problem described above, but it also breaks
t6023-merge-rename-nocruft.sh, which tries to merge "A" renamed to "B" in
HEAD and "A" modified in MERGE_HEAD, while ignoring an untracked file "A" in
the working tree. If we want to be able to do this, we have to handle the
other case after rename detection.

If the breakage is in merge-recursive but not in merge-resolve, my gut
feeling is that we should not be touching unpack-trees at all.  With luck
I may be able to find some time to take a look at this myself but right
now we are entertaining a guest, so....

-- >8 --
merge-recursive: do not clobber untracked working tree garbage

When merge-recursive wanted to create a new file in the work tree (either
as the final result, or a hint for reference purposes while delete/modify
conflicts), it unconditionally overwrote an untracked file in the working
tree.  Be careful not to lose whatever the user has that is not tracked.

Signed-off-by: Junio C Hamano <redacted>
---
 merge-recursive.c |   32 ++++++++++++++++++++++++++++++++
 1 files changed, 32 insertions(+), 0 deletions(-)

diff --git c/merge-recursive.c w/merge-recursive.c
index a0c804c..2da4333 100644
--- c/merge-recursive.c
+++ w/merge-recursive.c

@@ -447,6 +447,30 @@ static void flush_buffer(int fd, const char *buf, unsigned long size)
 	}
 }
 
+static int would_lose_untracked(const char *path)
+{
+	int pos = cache_name_pos(path, strlen(path));
+
+	if (pos < 0)
+		pos = -1 - pos;
+	while (pos < active_nr &&
+	       !strcmp(path, active_cache[pos]->name)) {
+		/*
+		 * If stage #0, it is definitely tracked.
+		 * If it has stage #2 then it was tracked
+		 * before this merge started.  All other
+		 * cases the path was not tracked.
+		 */
+		switch (ce_stage(active_cache[pos])) {
+		case 0:
+		case 2:
+			return 0;
+		}
+		pos++;
+	}
+	return file_exists(path);
+}
+
 static int make_room_for_path(const char *path)
 {
 	int status;

@@ -462,6 +486,14 @@ static int make_room_for_path(const char *path)
 		die(msg, path, "");
 	}
 
+	/*
+	 * Do not unlink a file in the work tree if we are not
+	 * tracking it.
+	 */
+	if (would_lose_untracked(path))
+		return error("refusing to lose untracked file at '%s'",
+			     path);
+
 	/* Successful unlink is good.. */
 	if (!unlink(path))
 		return 0;