External repositories: document label expansion
External repositories: document label expansion

Add a test demonstrating how a repository can provide a rule with
an implicit dependency on a target in its own repository in a way
that works both, locally and remotely without the need to know
the name of the repository the rule resides in.

Change-Id: I2446be1ba16a382576800f8141da17331e64f8b1
PiperOrigin-RevId: 186314462

meteorcloudy/bazel,bazelbuild/bazel,werkt/bazel,dropbox/bazel,werkt/bazel,safarmer/bazel,bazelbuild/bazel,davidzchen/bazel,dropbox/bazel,dslomov/bazel,cushon/bazel,ulfjack/bazel,davidzchen/bazel,dslomov/bazel-windows,dslomov/bazel-windows,dslomov/bazel,katre/bazel,perezd/bazel,cushon/bazel,ulfjack/bazel,perezd/bazel,katre/bazel,ulfjack/bazel,katre/bazel,dropbox/bazel,aehlig/bazel,cushon/bazel,dslomov/bazel,dslomov/bazel-windows,twitter-forks/bazel,meteorcloudy/bazel,werkt/bazel,bazelbuild/bazel,aehlig/bazel,ButterflyNetwork/bazel,katre/bazel,safarmer/bazel,dslomov/bazel,dslomov/bazel,davidzchen/bazel,meteorcloudy/bazel,twitter-forks/bazel,ButterflyNetwork/bazel,perezd/bazel,cushon/bazel,davidzchen/bazel,safarmer/bazel,twitter-forks/bazel,akira-baruah/bazel,ButterflyNetwork/bazel,ulfjack/bazel,perezd/bazel,akira-baruah/bazel,ulfjack/bazel,werkt/bazel,meteorcloudy/bazel,dropbox/bazel,twitter-forks/bazel,davidzchen/bazel,werkt/bazel,aehlig/bazel,safarmer/bazel,akira-baruah/bazel,cushon/bazel,ulfjack/bazel,akira-baruah/bazel,perezd/bazel,meteorcloudy/bazel,dslomov/bazel,ButterflyNetwork/bazel,katre/bazel,dslomov/bazel-windows,twitter-forks/bazel,meteorcloudy/bazel,dslomov/bazel-windows,davidzchen/bazel,aehlig/bazel,safarmer/bazel,werkt/bazel,dslomov/bazel-windows,ButterflyNetwork/bazel,dropbox/bazel,perezd/bazel,ButterflyNetwork/bazel,twitter-forks/bazel,aehlig/bazel,bazelbuild/bazel,akira-baruah/bazel,davidzchen/bazel,katre/bazel,dslomov/bazel,akira-baruah/bazel,cushon/bazel,perezd/bazel,aehlig/bazel,twitter-forks/bazel,bazelbuild/bazel,dropbox/bazel,aehlig/bazel,ulfjack/bazel,meteorcloudy/bazel,safarmer/bazel,bazelbuild/bazel