shortest: remove unnecessary check for revnum in isvalid() We now always disambiguating against revnums after we've found an otherwise valid prefix, so we can safely remove the early isrev() check in isvalid(). Differential Revision: https://phab.mercurial-scm.org/D3501

shortest: make pure code also disambigute against revnums at end This makes the pure code more similar to the native code in that it first finds a prefix that's unambiguous among nodeids and then adds hex digits until it no longer looks like a revnum. It will allow us to even better separate the disambiguation with revnums in a later patch. With this patch `hg log -r 0::50 -T '{shortest(node,1)}'` with no native code goes from 25s to 43s. It wasn't exactly usable to begin with, so I don't feel too bad about it. Differential Revision: https://phab.mercurial-scm.org/D3500