added remote variants

Todo item is done at last.

Might later want to think about testing some other types of remotes that
can be tested locally. The git remote itself is probably already well
enough tested by the test suite that testremote is not needed. Could
test things like bup, or rsync to a local directory. Or even external,
although that would require embedding an external special remote program
into the test suite..

doc/todo/test_testremote.mdwn

@@ -10,3 +10,5 @@ that could then be added to the test suite's TestTree.
 (See [[bugs/testremote_failures_starting_with_aeca7c220]])
 
 --[[Joey]]
+
+> [[done]] --[[Joey]]