Enable selective test execution in Mill's own CI

.config/mill-version

@@ -1 +1 @@
-0.12.3-58-4a0046
+0.12.3-58-4a0046

.github/actions/post-build-setup/action.yml

@@ -0,0 +1,30 @@
+# action.yml
+inputs:
+  java-version:
+    required: true
+    type: string
+
+  timeout-minutes:
+    default: 60
+    type: number
+
+  os:
+    type: string
+
+runs:
+  using: "composite"
+  steps:
+    - uses: actions/setup-java@v4
+      with:
+        java-version: ${{ inputs.java-version }}
+        distribution: temurin
+
+    - uses: actions/checkout@v4
+
+    # Need to fix cached artifact file permissions because github actions screws it up
+    # https://github.com/actions/upload-artifact/issues/38
+    - name: chmod executable
+      run: "chmod -R +x ."
+      shell: bash
+
+    - uses: coursier/cache-action@v6

.github/workflows/post-build-raw.yml

@@ -0,0 +1,36 @@
+name: post-build-raw
+on:
+  workflow_call:
+    inputs:
+      buildcmd:
+        default: ''
+        type: string
+      java-version:
+        required: true
+        type: string
+      os:
+        default: 'ubuntu-latest'
+        type: string
+      timeout-minutes:
+        default: 60
+        type: number
+
+jobs:
+  run:
+    runs-on: ${{ inputs.os }}
+    continue-on-error: false
+    timeout-minutes: ${{ inputs.timeout-minutes }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: ./.github/actions/post-build-setup
+        with:
+          java-version: ${{ inputs.java-version }}
+          os: ${{ inputs.os }}
+
+      - uses: actions/download-artifact@v4
+        with:
+          path: .
+          name: ${{ inputs.os }}-artifact
+
+      - run: ${{ inputs.buildcmd }}

.github/workflows/post-build-selective.yml

@@ -0,0 +1,69 @@
+name: post-build-selective
+on:
+  workflow_call:
+    inputs:
+      millargs:
+        default: ''
+        type: string
+      java-version:
+        required: true
+        type: string
+      os:
+        default: 'ubuntu-latest'
+        type: string
+      timeout-minutes:
+        default: 60
+        type: number
+      install-android-sdk:
+        default: false
+        type: boolean
+
+jobs:
+  run:
+    runs-on: ${{ inputs.os }}
+    continue-on-error: false
+    timeout-minutes: ${{ inputs.timeout-minutes }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: ./.github/actions/post-build-setup
+        with:
+          java-version: ${{ inputs.java-version }}
+          os: ${{ inputs.os }}
+
+      - uses: actions/download-artifact@v4
+        with:
+          path: .
+          name: ${{ inputs.os }}-artifact
+
+      - run: chmod -R 777 . # normalize permissions before and after upload/download-artifact
+
+      - uses: actions/download-artifact@v4
+        with:
+          path: out/mill-selective-execution
+          name: ${{ inputs.os }}-selective-execution-artifact
+
+      - run: mv out/mill-selective-execution/mill-selective-execution.json out/mill-selective-execution.json
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+
+      - uses: android-actions/setup-android@v3
+        if: ${{ inputs.install-android-sdk }}
+        with:
+          log-accepted-android-sdk-licenses: false
+
+      - run: ./mill -i -k selective.resolve ${{ inputs.millargs }}
+        if: github.event_name == 'pull_request'
+
+      - run: ./mill -i -k selective.run ${{ inputs.millargs }}
+        if: github.event_name == 'pull_request'
+
+      - run: ./mill -i -k ${{ inputs.millargs }}
+        if: github.event_name != 'pull_request'
+
+      - run: 'taskkill -f -im java* && rm -rf out/mill-server/*'
+        if: startsWith(inputs.os, 'windows')
+        shell: bash
+        continue-on-error: true

.github/workflows/pre-build.yml

@@ -0,0 +1,53 @@
+on:
+  workflow_call:
+    inputs:
+      compileargs:
+        default: '__.compile'
+        type: string
+      prepareargs:
+        default: '__.test'
+        type: string
+      java-version:
+        default: '11'
+        type: string
+      os:
+        type: string
+      timeout-minutes:
+        default: 60
+        type: number
+
+jobs:
+  run:
+    runs-on: ${{ inputs.os }}
+    timeout-minutes: ${{ inputs.timeout-minutes }}
+    steps:
+      - uses: actions/setup-java@v4
+        with:
+          java-version: ${{ inputs.java-version }}
+          distribution: temurin
+
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ github.base_ref }}
+
+      - run: chmod -R 777 . # normalize permissions before and after upload/download-artifact
+
+      - run: ./mill -i -k selective.prepare ${{ inputs.prepareargs }}
+
+      - uses: actions/[email protected]
+        with:
+          path: out/mill-selective-execution.json
+          name: ${{ inputs.os }}-selective-execution-artifact
+          include-hidden-files: true
+
+      - uses: actions/checkout@v4
+
+      - uses: coursier/cache-action@v6
+
+      - run: ./mill -i -k ${{ inputs.compileargs }}
+
+      - uses: actions/[email protected]
+        with:
+          path: .
+          name: ${{ inputs.os }}-artifact
+          include-hidden-files: true