grep: extract main search loop as searcher method
Still displayer part is in commands.grep(), the core grep logic is now
reusable. I'll revisit the displayer stuff later since it will be another
long series.
#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