Minor clarifications to git-filter-branch usage and doc

- Remove "DESTBRANCH" from usage, as it rewrites the branches given.
- Remove an = from an example usage, as the script doesn't understand
it.

Signed-off-by: Brian Gernhardt <benji@silverinsanity.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Documentation/git-filter-branch.txt b/Documentation/git-filter-branch.txt
index 915258f..8c43be6 100644
--- a/Documentation/git-filter-branch.txt
+++ b/Documentation/git-filter-branch.txt
@@ -120,7 +120,7 @@
 	tag name is expected on standard output.
 +
 The original tags are not deleted, but can be overwritten;
-use "--tag-name-filter=cat" to simply update the tags.  In this
+use "--tag-name-filter cat" to simply update the tags.  In this
 case, be very careful and make sure you have the old tags
 backed up in case the conversion has run afoul.
 +