gitsocial pm issue show rejects #commit:hash@branch for an issue in
the current repository.

It only succeeds with the full s3://bucket path prepended, the form
CLI.md reserves for another repository.

Reproduce with gitsocial pm issue create, then gitsocial pm issue
show on the printed #commit reference alone.

CLI.md documents #commit:hash@branch as sufficient for the current
repository.

Expected: gitsocial pm issue show resolves that reference without
the s3 URL.