It's important that people don't use `./rust-patches`
or `rust-patches/*`, since the first won't match
the regex and the second the shell will expand.

Easier to use than manually specifying,
but doesn't handle non-top-level cargo.toml patches.

Should we rely on conventions of users putting
all of their patches in one location? As long as they aren't
intermixed with their source, it should be pretty easy
to guess.

This reverts commit f50ef2c.

This reverts commit 71ae809.