Add CI builder image and use it in the pipeline

builder.Dockerfile bakes the build step's dependencies into
git.teletype.hu/internal/* so the pipeline no longer installs
packages on every run.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -29,4 +29,19 @@ The pipeline uploads `$(PROJECT)-$(VERSION).lua`, `.tic`, `.html.zip`
 and `-docs.zip` to the droparea, then triggers
 `/update?platform=tic80&name=$(PROJECT)&version=$(VERSION)`.
 
+## Builder image
+
+The export step uses the TIC-80 Pro image
+(`git.teletype.hu/internal/tic80pro`, built from the
+`tic80pro-dockerfile` repo). For the lint / minify / docs steps,
+`builder.Dockerfile` bakes Lua 5.4 + luacheck + ldoc + zip into
+`git.teletype.hu/internal/tic80-luatools`, so the pipeline no longer
+runs luarocks (and a C compiler install) on every run:
+
+```sh
+docker build --platform linux/amd64 -f builder.Dockerfile \
+  -t git.teletype.hu/internal/tic80-luatools:latest .
+docker push git.teletype.hu/internal/tic80-luatools:latest
+```
+
 Detailed documentation lives on the wiki: `/development/tic80`.

builder.Dockerfile

@@ -0,0 +1,24 @@
+# CI toolbox image for the TIC-80 pipeline's lint / minify / docs steps:
+# Lua 5.4 with luacheck and ldoc preinstalled, so the pipeline does not
+# run luarocks (and a C compiler install) on every run.
+#
+# The export step keeps using the separate TIC-80 Pro image
+# (git.teletype.hu/internal/tic80pro, built from the tic80pro-dockerfile
+# repo) — this image only covers the Lua tooling around it.
+#
+# Build & push (the CI runner is linux/amd64):
+#   docker build --platform linux/amd64 -f builder.Dockerfile \
+#     -t git.teletype.hu/internal/tic80-luatools:latest .
+#   docker push git.teletype.hu/internal/tic80-luatools:latest
+
+FROM alpine:3.22
+
+RUN apk add --no-cache make zip curl git lua5.4 lua5.4-dev luarocks gcc musl-dev \
+ && ln -sf /usr/bin/lua5.4 /usr/bin/lua \
+ && ln -sf /usr/bin/luarocks-5.4 /usr/bin/luarocks \
+ && luarocks install luacheck \
+ && luarocks install ldoc
+
+WORKDIR /workspace
+
+CMD ["/bin/sh"]

example-woodpecker.yaml

@@ -6,28 +6,18 @@ steps:
       - 'make ci-version'
 
   - name: lint
-    image: alpine
+    image: git.teletype.hu/internal/tic80-luatools:latest
     commands:
-      - 'apk add --no-cache make lua5.4 lua5.4-dev luarocks gcc musl-dev'
-      - 'ln -sf /usr/bin/lua5.4 /usr/bin/lua'
-      - 'ln -sf /usr/bin/luarocks-5.4 /usr/bin/luarocks'
-      - 'luarocks install luacheck'
       - 'make ci-lint'
 
   - name: minify
-    image: alpine
+    image: git.teletype.hu/internal/tic80-luatools:latest
     commands:
-      - 'apk add --no-cache make lua5.4 curl'
-      - 'ln -sf /usr/bin/lua5.4 /usr/bin/lua'
       - 'make ci-minify'
 
   - name: docs
-    image: alpine
+    image: git.teletype.hu/internal/tic80-luatools:latest
     commands:
-      - 'apk add --no-cache make lua5.4 lua5.4-dev luarocks gcc musl-dev zip'
-      - 'ln -sf /usr/bin/lua5.4 /usr/bin/lua'
-      - 'ln -sf /usr/bin/luarocks-5.4 /usr/bin/luarocks'
-      - 'luarocks install ldoc'
       - 'make ci-docs'
 
   - name: export