Makefile: add a target for running a shell inside docker

Change-Id: If9d72e1a87fef19e78dc4173705d2da831de7575
Reviewed-on: https://go-review.googlesource.com/c/pkgsite-metrics/+/471121
Run-TryBot: Jonathan Amsterdam <jba@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Maceo Thompson <maceothompson@google.com>
diff --git a/Makefile b/Makefile
index bff1134..1cdd2d9 100644
--- a/Makefile
+++ b/Makefile
@@ -48,9 +48,15 @@
 	touch $@
 
 # Run the docker image locally, for testing.
+# The worker will start and listen at port 8080.
 docker-run: docker-build
 	docker run --rm --privileged -p 8080:8080 $(IMAGE)
 
+# Run the docker image and enter an interactive shell.
+# The worker does not start.
+docker-run-shell: docker-build
+	docker run --rm -it --privileged ecosystem-worker-test /bin/bash
+
 # Run the docker image in the background, waiting until the server is ready.
 docker-run-bg: docker-build
 	docker run --detach --rm --privileged -p 8080:8080 $(IMAGE) > /tmp/ecosystem-docker-container-id