test: introduce a new flag to display env variable line per line
It's easier to conditionalize some of the environment variables per Mercurial
version once there is only one value per line.
Differential Revision: https://phab.mercurial-scm.org/D5453
#require test-repo jshint hg10
$ . "$TESTDIR/helpers-testrepo.sh"
run jshint on all tracked files ending in .js except vendored dependencies
$ cd "`dirname "$TESTDIR"`"
$ testrepohg locate 'set:**.js' \
> 2>/dev/null \
> | xargs jshint