Fix pull from a Project

[elsylambert]

Fix pull from a Project

[mvahowe]

What we need here is a way to link a locally-created repo to the equivalent repo that is downloaded at some later date. In other words

• I make a repo
• I push it
• Someone else works on it and makes changes
• I download those changes
• Now I want to merge those changes to my local repo.

This works if you start with a download because "make local copy" sets up remotes pointing back to the downloaded copy. Look at the "make local copy" code for details.

For now I think we could deduce the local path to the downloaded copy by modifying the path of the local copy. ie _local_/_local_/foo probably has a downloaded equivalent called _local_/_downloaded_/foo or _local_/_sideloaded_/foo. So we could check if either of those exist and provide a button to link.

Ideally we'd look at the commit history because the two repos must have common commits. But let's do that if/when we need it.