New matching options --excludesamecontent and --includesamecontent

The normalisation of filenames turns out to be the tricky part here,
because the associated files coming out of the keys db may look like
"./foo/bar" or "../bar". For the former to match a glob like "foo/*",
it needs to be normalised.

Note that, on windows, normalise "./foo/bar" = "foo\\bar"
which a glob like "foo/*" won't match. So the glob is matched a second
time, on the toInternalGitPath, so allowing the user to provide a glob
with the slashes in either direction. However, this still won't support
some wacky edge cases like the user providing a glob of "foo/bar\\*"

Sponsored-by: Dartmouth College's Datalad project

doc/todo/option_to___96__drop_path__96___to_not_drop___34__all_copies__34__.mdwn

@@ -6,3 +6,5 @@ In our repositories/workflows we quite often encounter cases where multiple subf
 
 [[!meta author=yoh]]
 [[!tag projects/datalad]]
+
+> [[done]] --[[Joey]]