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
$ hg init a
$ cd a
$ echo a > a
$ hg ci -Am0
adding a
$ echo b > b
$ hg ci -Am1
adding b
$ hg tag -r0 default
warning: tag default conflicts with existing branch name
$ hg log
changeset: 2:30a83d1e4a1e
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added tag default for changeset f7b1eb17ad24
changeset: 1:925d80f479bb
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 1
changeset: 0:f7b1eb17ad24
tag: default
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 0
$ hg update 'tag(default)'
0 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ hg parents
changeset: 0:f7b1eb17ad24
tag: default
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 0
$ hg update 'branch(default)'
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg parents
changeset: 2:30a83d1e4a1e
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added tag default for changeset f7b1eb17ad24
$ cd ..