shortest: make {shortest("fffffffff")} work again
{shortest("fffffffff")} should shorten it to the shortest unambiguous
prefix for the working directory. It used to do that until I broke it
in 7b2955624777 (scmutil: make shortesthexnodeidprefix() take a full
binary nodeid, 2018-04-14), when we started returning the full hex
nodeid for any working directory prefix shorter than 40 hex
digits. This patch fixes it by catching WdirUnsupported
specifically.
Differential Revision: https://phab.mercurial-scm.org/D3455
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ echo 'base' > base
$ hg ci -Ambase
adding base
$ hg qnew -mmqbase mqbase
$ hg qsave
$ hg qrestore 2
restoring status: hg patches saved state