unpack-trees: handle failure in verify_absent

Commit 203a2fe1 (Allow callers of unpack_trees() to handle failure)
changed the "die on error" behavior to "return failure code".
verify_absent did not handle errors returned by
verify_clean_subdirectory, however.

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

t/t1001-read-tree-m-2way.sh

@@ -341,4 +341,28 @@ test_expect_success \
      check_cache_at DF/DF dirty &&
      :'
 
+test_expect_success \
+    'a/b (untracked) vs a case setup.' \
+    'rm -f .git/index &&
+     : >a &&
+     git update-index --add a &&
+     treeM=`git write-tree` &&
+     echo treeM $treeM &&
+     git ls-tree $treeM &&
+     git ls-files --stage >treeM.out &&
+
+     rm -f a &&
+     git update-index --remove a &&
+     mkdir a &&
+     : >a/b &&
+     treeH=`git write-tree` &&
+     echo treeH $treeH &&
+     git ls-tree $treeH'
+
+test_expect_success \
+    'a/b (untracked) vs a, plus c/d case test.' \
+    '! git read-tree -u -m "$treeH" "$treeM" &&
+     git ls-files --stage &&
+     test -f a/b'
+
 test_done

unpack-trees.c

@@ -587,7 +587,7 @@ static int verify_absent(struct cache_entry *ce, const char *action,
 		return 0;
 
 	if (!lstat(ce->name, &st)) {
-		int cnt;
+		int ret;
 		int dtype = ce_to_dtype(ce);
 		struct cache_entry *result;
 
@@ -615,7 +615,9 @@ static int verify_absent(struct cache_entry *ce, const char *action,
 			 * files that are in "foo/" we would lose
 			 * it.
 			 */
-			cnt = verify_clean_subdirectory(ce, action, o);
+			ret = verify_clean_subdirectory(ce, action, o);
+			if (ret < 0)
+				return ret;
 
 			/*
 			 * If this removed entries from the index,
@@ -634,7 +636,7 @@ static int verify_absent(struct cache_entry *ce, const char *action,
 			 * We need to increment it by the number of
 			 * deleted entries here.
 			 */
-			o->pos += cnt;
+			o->pos += ret;
 			return 0;
 		}