Support permalinks from a git tag

When trying to create a permalink for https://github.dev/python/cpython/blob/v3.8.12/Objects/typeobject.c#L921 (note the v3.8.12 tag), I get the following message:

On github.com I can create the link without issue, so I would love to be able to do the same from github.dev .

[joyceerhl]

Running GHPRI out of sources against latest RemoteHub and can confirm that GHPRI permalink generation now works when opening the following GitHub urls in RemoteHub (previously, if you had any of these open, permalink generation did not work):

• https://github.com/python/cpython/commit/304f5b63e904c3ab0b746ef7ad58c5c2ff0154a8
• https://github.com/python/cpython/tree/v3.8.12/Objects/typeobject.c#L921
• https://github.com/python/cpython/blob/v3.8.12/Objects/typeobject.c#L921
• https://github.com/python/cpython/blob/aeb66c1abbf4ec214e2e80eb972546996d1a1571/Lib/test/test_finalization.py

(The tag urls didn’t work because no upstream was found and the repository metadata HEAD commit was wrong; the commit urls didn’t work because no upstream was found.)

[joyceerhl]

Something must have been stale somewhere as the one I saw while debugging was the old OID.

This is because RemoteHub caches metadata on disk and doesn’t invalidate that cache appropriately. I have pushed a fix in RemoteHub to ignore cached metadata and ask for the latest info from network when first initializing the repo. Users who have already seen the bad metadata once like @brettcannon should just be able to update RemoteHub and reload.