Add multi-package Alpine packaging

packaging/alpine/blueprint/README.md

@@ -0,0 +1,26 @@
+# Alpine Package Blueprint
+
+Copy this directory to `packaging/alpine/local/<pkgname>/` and replace the
+placeholder values before building.
+
+Required:
+
+- `APKBUILD`
+
+Optional package-local hooks:
+
+- `scripts/test-install.sh` validates README-style installation instructions.
+- `scripts/update-generated-sources.sh` refreshes generated files that are
+  listed in `source=`.
+
+Repo-level tasks discover packages from `packaging/alpine/local/*/APKBUILD`.
+Limit a task to one or more packages with:
+
+```sh
+ALPINE_PACKAGE=<pkgname> mise run apk:build
+ALPINE_PACKAGES="<pkg-a> <pkg-b>" mise run apk:build-all
+ALPINE_PACKAGE=<pkgname> mise run apk:test-install
+```
+
+For compiled software, put normal Alpine build logic in `build()`, `check()`,
+and `package()` and declare build tools in `makedepends`.