Attempt to pull maintained packaged if referenced at newer version

[medikoo]

If package depends on a maintained package, but refers to newer version than one found locally, it'll be good to attempt git pull on that maintained package, but only if it's on its default branch and git status is clean.

[medikoo]

Wanted to implement that but it appears as tricky, e.g. there can be the case where at first pass (e.g. when inspected as deep dependency) maintained package is referenced at supported version, and then at second pass (as a top level dependency) it appears as outdated.
Currently there's no mechanism to revisit package setup in such case, which makes it troublesome to address. Also pull operation is sort of destructive, and it'll be good to make it only for top level dependencies.

Still I've made an improvement, and with 3a6d7a3 we now signal with notice log such case, so at least it's not treated silently.