debugcommands: fix a missing b prefix
This wasn't causing any immediate problems because of the source
transformer, but I noticed the inconsistency and it bugged me.
# skip-blame just a b prefix
Differential Revision: https://phab.mercurial-scm.org/D4255
#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