t7415: rename to expand scope

This script has already expanded beyond its original intent of ".. in
submodule names" to include other malicious submodule bits. Let's update
the name and description to reflect that, as well as the fact that we'll
soon be adding similar tests for other dotfiles (.gitattributes, etc).
We'll also renumber it to move it out of the group of submodule-specific
tests.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7450-bad-git-dotfiles.sh

@@ -1,9 +1,16 @@
 #!/bin/sh
 
-test_description='check handling of .. in submodule names
+test_description='check broken or malicious patterns in .git* files
 
-Exercise the name-checking function on a variety of names, and then give a
-real-world setup that confirms we catch this in practice.
+Such as:
+
+  - presence of .. in submodule names;
+    Exercise the name-checking function on a variety of names, and then give a
+    real-world setup that confirms we catch this in practice.
+
+  - nested submodule names
+
+  - symlinked .gitmodules, etc
 '
 . ./test-lib.sh
 . "$TEST_DIRECTORY"/lib-pack.sh