unpack_trees(): allow callers to differentiate worktree errors from merge errors

Instead of uniformly returning -1 on any error, this teaches
unpack_trees() to return -2 when the merge itself is Ok but worktree
refuses to get updated.

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

diff --git a/unpack-trees.c b/unpack-trees.c
index 0de5a31c0b68f87491e540fdc1978809fee00240..cba0aca062f201c5cd5f8799f2190d4a6f06e7c7 100644 (file)
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -358,8 +358,13 @@ static int unpack_failed(struct unpack_trees_options *o, const char *message)
        return -1;
 }
 
+/*
+ * N-way merge "len" trees.  Returns 0 on success, -1 on failure to manipulate the
+ * resulting index, -2 on failure to reflect the changes to the work tree.
+ */
 int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
 {
+       int ret;
        static struct cache_entry *dfc;
 
        if (len > MAX_UNPACK_TREES)
@@ -404,11 +409,10 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
                return unpack_failed(o, "Merge requires file-level merging");
 
        o->src_index = NULL;
-       if (check_updates(o))
-               return -1;
+       ret = check_updates(o) ? (-2) : 0;
        if (o->dst_index)
                *o->dst_index = o->result;
-       return 0;
+       return ret;
 }
 
 /* Here come the merge functions */