Allow source build in GitHub actions

CHANGELOG.md

@@ -9,6 +9,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- The GitHub action can now install unreleased builds:
+  passing a commit SHA or branch name as `version` clones the repository at that ref and builds from source with Go.
+  Release tags (`vX.Y.Z`) and `latest` still download pre-built binaries.
+
 - The tar write functions (`tarDirInc`, `tarDirExc`, `tarPack`) now accept a
   dictionary destination `{path: str|path, compress?: bool}`, where `compress`
   overrides the extension-based gzip inference in either direction — useful

action.yml

@@ -2,14 +2,29 @@ name: 'Setup mshell'
 description: 'Install the mshell concatenative shell language'
 inputs:
   version:
-    description: 'Version to install (e.g., v0.1.0). Defaults to latest.'
+    description: >
+      Version to install. A release tag (e.g., v0.1.0) or 'latest' downloads a
+      pre-built binary. Anything else (a commit SHA or branch name) is built
+      from source with Go. Defaults to latest.
     required: false
     default: 'latest'
 runs:
   using: 'composite'
   steps:
+    - name: Determine install mode
+      id: mode
+      shell: bash
+      run: |
+        VERSION="${{ inputs.version }}"
+        if [ "$VERSION" = "latest" ] || [ "${VERSION#v}" != "$VERSION" ]; then
+          echo "mode=release" >> $GITHUB_OUTPUT
+        else
+          echo "mode=source" >> $GITHUB_OUTPUT
+        fi
+
     - name: Determine platform
       id: platform
+      if: steps.mode.outputs.mode == 'release'
       shell: bash
       run: |
         case "${{ runner.os }}-${{ runner.arch }}" in
@@ -21,7 +36,8 @@ runs:
           *) echo "Unsupported platform: ${{ runner.os }}-${{ runner.arch }}" && exit 1 ;;
         esac
 
-    - name: Download and install mshell
+    - name: Download mshell release
+      if: steps.mode.outputs.mode == 'release'
       shell: bash
       env:
         ACTION_REPO: ${{ github.action_repository }}
@@ -38,6 +54,47 @@ runs:
         mkdir -p "$HOME/.mshell/bin"
         curl -sL "$URL" | tar -xz -C "$HOME/.mshell/bin"
 
+    - name: Checkout mshell source
+      if: steps.mode.outputs.mode == 'source'
+      shell: bash
+      env:
+        ACTION_REPO: ${{ github.action_repository }}
+      run: |
+        VERSION="${{ inputs.version }}"
+        SRC_DIR="$RUNNER_TEMP/mshell-src"
+        rm -rf "$SRC_DIR"
+        git clone "https://github.com/${ACTION_REPO}" "$SRC_DIR"
+        git -C "$SRC_DIR" checkout "$VERSION"
+
+    - name: Set up Go
+      if: steps.mode.outputs.mode == 'source'
+      uses: actions/setup-go@v5
+      with:
+        go-version-file: ${{ runner.temp }}/mshell-src/mshell/go.mod
+        cache: false
+
+    - name: Build mshell from source
+      if: steps.mode.outputs.mode == 'source'
+      shell: bash
+      run: |
+        SRC_DIR="$RUNNER_TEMP/mshell-src"
+        mkdir -p "$HOME/.mshell/bin"
+
+        if [ "${{ runner.os }}" = "Windows" ]; then
+          BIN="mshell.exe"
+        else
+          BIN="mshell"
+        fi
+
+        cd "$SRC_DIR/mshell"
+        go build -o "$HOME/.mshell/bin/$BIN"
+
+        # Releases ship std.msh in the tarball; for source builds take it from the repo.
+        cp "$SRC_DIR/lib/std.msh" "$HOME/.mshell/bin/std.msh"
+
+    - name: Install mshell
+      shell: bash
+      run: |
         # Create symlinks so both msh and mshell work
         cd "$HOME/.mshell/bin"
         if [ -f mshell ]; then
@@ -76,7 +133,7 @@ runs:
         mkdir -p "$DATA_DIR/$MSH_VERSION"
         mkdir -p "$CONFIG_DIR/$MSH_VERSION"
 
-        # std.msh is included in the release tarball; move it into the versioned startup location.
+        # std.msh is placed in the bin directory by both install modes; move it into the versioned startup location.
         mv "$HOME/.mshell/bin/std.msh" "$DATA_DIR/$MSH_VERSION/std.msh"
 
         # Create an empty init.msh so startup succeeds on first run.

doc/getting-started.inc.html

@@ -96,6 +96,21 @@ <h1 id="getting-started-github-actions">GitHub Actions <a class="section-link" h
 The action downloads the pre-built binary for the runner platform and installs the matching startup files automatically.
 </p>
 
+<p>
+To use a build that has not been released yet, pass a commit SHA or branch name as the version.
+Anything that is not <code>latest</code> and does not start with <code>v</code> is treated as a git ref:
+the action clones the repository at that ref and builds from source with Go
+(installed automatically via <code>actions/setup-go</code>).
+</p>
+
+<pre>
+<code><span class="yaml-key">steps:</span>
+  - <span class="yaml-key">uses:</span> mitchpaulus/mshell@main
+    <span class="yaml-key">with:</span>
+      <span class="yaml-key">version:</span> a087dc2f
+  - <span class="yaml-key">run:</span> msh script.msh</code>
+</pre>
+
 <h1 id="getting-started-editor-support">Editor Support <a class="section-link" href="#getting-started-editor-support" aria-label="Permalink">§</a> <a class="back-to-top" href="#getting-started-top">Back to top</a></h1>
 
 <p>