import: Check gitignores when importing trees from special remotes

import: Check gitignores when importing trees from special remotes

It seemed best to do this, for consistency with every other way files can
get into a git-annex repo. Although it's just a bit strange that a local
.gitignore file affects the pseudo-commits made for the remote that's
imported from.

This commit was sponsored by Brett Eisenberg on Patreon.