Provide way of building zigup through Docker

.dockerignore

@@ -0,0 +1,5 @@
+/.git
+/zig-cache
+/zig-out
+/dep
+/scratch

.github/workflows/docker.yml

@@ -0,0 +1,39 @@
+name: Docker
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+    types:
+      - opened
+      - synchronize
+      - reopened
+      - unlocked
+
+jobs:
+  build:
+    concurrency: 
+      group: docker-${{ github.event.pull_request.number || github.sha }}
+      cancel-in-progress: true
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Build zigup on Docker
+        run: docker build -t zigup .
+
+      - name: Pull zigup from the built image
+        run: |
+          container="$(docker container create zigup)"
+          docker container cp "$container":/zigup/zig-out/bin/zigup .
+
+      - name: Verify zigup binary
+        run: |
+          if ldd ./zigup; then
+            >&2 echo "zigup was not compiled as a static binary"
+            exit 1
+          fi
+          ./zigup --help

Dockerfile

@@ -0,0 +1,29 @@
+FROM docker.io/library/alpine:latest
+
+# Update the system
+RUN apk update && apk upgrade
+
+# Initialize build tools directory
+RUN mkdir -p /tools
+WORKDIR /tools
+
+# Install Zig
+RUN apk add --no-cache curl tar xz
+ARG ZIG_VERSION=0.11.0-dev.1507+6f13a725a
+RUN curl -sSfL \
+      https://ziglang.org/builds/zig-linux-x86_64-"$ZIG_VERSION".tar.xz \
+      -o zig.tar.xz && \
+    tar -xf zig.tar.xz && \
+    mv zig-linux-x86_64-"$ZIG_VERSION" zig
+ENV PATH="/tools/zig:$PATH"
+
+# Build zigup
+RUN apk add --no-cache git
+ARG ZIGUP_TARGET=x86_64-linux
+ARG ZIGUP_BUILD_FLAGS=-Drelease-safe
+COPY . /zigup
+WORKDIR /zigup
+RUN zig build -Dfetch -Dtarget="$ZIGUP_TARGET" $ZIGUP_BUILD_FLAGS
+ENV PATH="/zigup/zig-out/bin:$PATH"
+
+ENTRYPOINT ["/zigup/zig-out/bin/zigup"]

README.md

@@ -40,14 +40,34 @@ zigup stores each compiler in a global "install directory" in a versioned subdir
 zigup makes the zig program available by creating an entry in a directory that occurs in the `PATH` environment variable.  On posix systems this entry is a symlink to one of the `zig` executables in the install directory.  On windows this is an executable that forwards invocations to one of the `zig` executables in the install directory.
 
 Both the "install directory" and "path link" are configurable through command-line options `--install-dir` and `--path-link` respectively.
+
 # Building
 
+## Directly on your host
+
 Run `zig build` to build, `zig build test` to test and install with:
 ```
 # install to a bin directory with
 cp zig-out/bin/zigup BIN_PATH
 ```
 
+## Through Docker
+
+```bash
+# Build for the default target (x86_64-linux)
+docker build -t zigup .
+# Or specify a custom target through ZIGUP_TARGET
+# docker build -t zigup --build-arg ZIGUP_TARGET=macos-x86_64 .
+
+# Copy zigup from the Docker image to your host
+container="$(docker container create zigup)"
+docker container cp "$container":/zigup/zig-out/bin/zigup .
+docker container rm "$container"
+
+# Use zigup  
+./zigup --help
+```
+
 # TODO
 
 * set/remove compiler in current environment without overriding the system-wide vesrion.