Ensure the data directory is present when creating a project archive

This is needed by the `Makefile` to save the blank terrain file in
after downloading it.

.gitignore

@@ -2,5 +2,4 @@ bin
 pkg
 server
 src/github.com
-data/smallterrain-blank.terrain
 src/cesium-terrain-server/assets/

Makefile

@@ -26,7 +26,7 @@ docker-local: docker/local/cesium-terrain-server.tar.gz docker/local/Cesium-$(ce
 docker/local/Cesium-$(cesium_version).zip: docker/cesium-version.txt
 	curl --location https://cesiumjs.org/releases/Cesium-$(cesium_version).zip > docker/local/Cesium-$(cesium_version).zip
 
-docker/local/cesium-terrain-server.tar.gz:
-	tar -czvf docker/local/cesium-terrain-server.tar.gz docker/cesium-version.txt src/cesium-terrain-server Makefile
+docker/local/cesium-terrain-server.tar.gz: src/cesium-terrain-server/server.go src/cesium-terrain-server/assets/assets.go
+	tar --exclude data/* -czvf docker/local/cesium-terrain-server.tar.gz docker/cesium-version.txt src/cesium-terrain-server Makefile data
 
 .PHONY: docker-local

data/.gitignore

@@ -0,0 +1,4 @@
+# Ignore everything we don't need in this directory
+smallterrain-blank.terrain
+# Except this file
+!.gitignore