Make version explicit

Dockerfile

@@ -5,11 +5,10 @@ ENV DOTNET_CLI_TELEMETRY_OPTOUT 1
 RUN apt-get update \
     && apt-get -y install jq
 
+ARG OSU_VERSION
+ENV OSU_VERSION=$OSU_VERSION
 
-ARG CACHEBUST=1
-ENV CACHEBUST=$CACHEBUST
-
-RUN OSU_VERSION=$(curl -s https://api.github.com/repos/ppy/osu/releases/latest | jq -r .tag_name) \
+RUN echo "Downloading and building osu! ${OSU_VERSION}" >&2 \
     && git clone --depth=1 --single-branch -b ${OSU_VERSION} https://github.com/ppy/osu \
     && cd osu \
     && dotnet publish \

README.md

@@ -2,6 +2,16 @@
 
 ## How to use
 
+### Building
+
+Using podman/buildah:
+
+    buildah build --format docker --layers -t osu --build-arg OSU_VERSION=2024.412.1
+
+Change `2024.412.1` to the newest osu! version.
+
+### Running
+
 Place `run.sh` in a directory of your choice. On first run, the directories
 `data` and `import` will be created.