[PATCH] Better errors when trying to merge a submodule

[Finn Arne Gangstad <finnag@pvv.org>]

Instead of dying with weird errors when trying to merge submodules from a
supermodule, emit errors that show what the problem is.

Signed-off-by: Finn Arne Gangstad <finnag@pvv.org>
---

If you try to merge a submodule from a supermodule, you get some very
strange error messages. With this patch you get a nice clean error
message indicating that this isn't supported instead.


 git-merge-one-file.sh |    7 +++++++
 merge-recursive.c     |    2 ++
 2 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/git-merge-one-file.sh b/git-merge-one-file.sh
index 1e7727d..7aee342 100755
--- a/git-merge-one-file.sh
+++ b/git-merge-one-file.sh
@@ -82,6 +82,13 @@ case "${1:-.}${2:-.}${3:-.}" in
 		;;
 	esac
 
+	case ",$6,$7," in
+	*,160000,*)
+		echo "ERROR: $4: Not merging submodule."
+		exit 1
+		;;
+	esac
+
 	src2=`git-unpack-file $3`
 	case "$1" in
 	'')
diff --git a/merge-recursive.c b/merge-recursive.c
index 9a1e2f2..ecae8ea 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -1046,6 +1046,8 @@ static struct merge_file_info merge_file(struct diff_filespec *o,
 
 			free(result_buf.ptr);
 			result.clean = (merge_status == 0);
+                } else if (S_ISGITLINK(a->mode) || S_ISGITLINK(b->mode)) {
+                        die("cannot merge submodules!");
 		} else {
 			if (!(S_ISLNK(a->mode) || S_ISLNK(b->mode)))
 				die("cannot merge modes?");
-- 
1.5.3.7.1149.g591a-dirty