shortest: don't keep checking for longer prefix if node doesn't exist (API) If revlog.shortest() is called with an invalid nodeid, we keep checking if longer and longer prefixes are valid. We call revlog._partialmatch() for each prefix. That function will give us None if the node doesn't exist (and a RevlogError if it's ambiguous), so there's no need to keep checking. This patch instead makes revlog.shortest() raise a LookupError is the node does not exist, and updates the caller to handle it. Before this patch, revlog.shortest() would return the full hexnode for nonexistent nodeids. By the same reasoning as in 7b2955624777 (scmutil: make shortesthexnodeidprefix() take a full binary nodeid, 2018-04-14), it's not revlog.shortest() that should decide how to present nonexistent nodeids, so that's now moved to the template function. This should speed up cases where {shortest()} is applied to an invalid nodeid, but I couldn't think of a reasonable case where that would happen. Differential Revision: https://phab.mercurial-scm.org/D3461