Support a merge with conflicting gitlink change

merge-recursive did not support merging trees that have conflicting
changes in submodules they contain, and died.  Support it exactly the
same way as how it handles conflicting symbolic link changes --- mark it
as a conflict, take the tentative result from the current side, and
letting the caller resolve the conflict, without dying in merge_file()
function.

Also reword the error message issued when merge_file() has to die
because it sees a tree entry of type it does not support yet.

[jc: fixed up initial draft by Finn Arne Gangstad]

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/merge-recursive.c b/merge-recursive.c
index 9a1e2f269d..2a58dad3f4 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -1046,14 +1046,16 @@ static struct merge_file_info merge_file(struct diff_filespec *o,
 
 			free(result_buf.ptr);
 			result.clean = (merge_status == 0);
-		} else {
-			if (!(S_ISLNK(a->mode) || S_ISLNK(b->mode)))
-				die("cannot merge modes?");
-
+		} else if (S_ISGITLINK(a->mode)) {
+			result.clean = 0;
+			hashcpy(result.sha, a->sha1);
+		} else if (S_ISLNK(a->mode)) {
 			hashcpy(result.sha, a->sha1);
 
 			if (!sha_eq(a->sha1, b->sha1))
 				result.clean = 0;
+		} else {
+			die("unsupported object type in the tree");
 		}
 	}