mv: prevent mismatched data when ignoring errors.

We shrink the source and destination arrays, but not the modes or
submodule_gitfile arrays, resulting in potentially mismatched data.  Shrink
all the arrays at the same time to prevent this.  Add tests to ensure the
problem does not recur.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/mv.c

@@ -231,6 +231,11 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 					memmove(destination + i,
 						destination + i + 1,
 						(argc - i) * sizeof(char *));
+					memmove(modes + i, modes + i + 1,
+						(argc - i) * sizeof(enum update_mode));
+					memmove(submodule_gitfile + i,
+						submodule_gitfile + i + 1,
+						(argc - i) * sizeof(char *));
 					i--;
 				}
 			} else

t/t7001-mv.sh

@@ -294,7 +294,8 @@ test_expect_success 'setup submodule' '
 	git submodule add ./. sub &&
 	echo content >file &&
 	git add file &&
-	git commit -m "added sub and file"
+	git commit -m "added sub and file" &&
+	git branch submodule
 '
 
 test_expect_success 'git mv cannot move a submodule in a file' '
@@ -442,4 +443,14 @@ test_expect_success 'mv --dry-run does not touch the submodule or .gitmodules' '
 	git diff-files --quiet -- sub .gitmodules
 '
 
+test_expect_success 'mv -k does not accidentally destroy submodules' '
+	git checkout submodule &&
+	mkdir dummy dest &&
+	git mv -k dummy sub dest &&
+	git status --porcelain >actual &&
+	grep "^R  sub -> dest/sub" actual &&
+	git reset --hard &&
+	git checkout .
+'
+
 test_done