ci(aur): publish the AUR packages from CI

A release tag now updates and pushes all three AUR packages once the
GitHub release exists, then commits the refreshed recipes back to main.
A push to main that changes the -git recipe publishes that package
alone; plain upstream commits need no AUR push because its pkgver()
follows git at build time.

Needs the AUR_SSH_PRIVATE_KEY repository secret.

.github/workflows/aur.yml

@@ -0,0 +1,101 @@
+name: AUR
+
+on:
+  # The -git package computes its pkgver from git at build time, so a new commit
+  # upstream needs no AUR push. Only a changed -git recipe is published.
+  push:
+    branches: [main]
+    paths:
+      - 'packaging/aur/proton-drive-for-linux-git/**'
+  # Called by release.yml once the GitHub release and its assets exist.
+  workflow_call:
+    inputs:
+      version:
+        required: true
+        type: string
+    secrets:
+      AUR_SSH_PRIVATE_KEY:
+        required: true
+  workflow_dispatch:
+    inputs:
+      version:
+        description: 'Release to publish, such as 2.1.0. Leave empty to publish only the -git package.'
+        required: false
+        type: string
+
+permissions:
+  contents: write
+
+concurrency:
+  group: aur
+  cancel-in-progress: false
+
+jobs:
+  publish:
+    name: Publish AUR packages
+    runs-on: ubuntu-24.04
+    container: archlinux:base-devel
+    env:
+      # makepkg refuses to run as root, so the packaging steps run as `builder`.
+      HOME: /home/builder
+      VERSION: ${{ inputs.version }}
+
+    steps:
+      - name: Install packaging tools
+        run: pacman -Syu --noconfirm --needed git openssh pacman-contrib
+
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          # The updated recipes are committed back to main, not to the tag.
+          ref: main
+
+      - name: Create build user
+        run: |
+          useradd --create-home builder
+          chown -R builder: "$GITHUB_WORKSPACE"
+
+      - name: Configure AUR access
+        env:
+          AUR_SSH_PRIVATE_KEY: ${{ secrets.AUR_SSH_PRIVATE_KEY }}
+        run: |
+          install -d -m700 -o builder -g builder "$HOME/.ssh"
+          printf '%s\n' "$AUR_SSH_PRIVATE_KEY" > "$HOME/.ssh/aur"
+          cat > "$HOME/.ssh/config" <<'EOF'
+          Host aur.archlinux.org
+            IdentityFile ~/.ssh/aur
+            User aur
+          EOF
+          # Pin the host key to the fingerprint published on aur.archlinux.org.
+          ssh-keyscan -t ed25519 aur.archlinux.org > "$HOME/.ssh/known_hosts"
+          ssh-keygen -lf "$HOME/.ssh/known_hosts" | grep -q 'SHA256:RFzBCUItH9LZS0cKB5UE6ceAYhBD5C8GeOBip8Z11+4'
+          chown -R builder: "$HOME/.ssh"
+          chmod 600 "$HOME/.ssh/aur"
+          runuser -u builder -- git config --global user.name 'Nils Pukropp'
+          runuser -u builder -- git config --global user.email 'contact@narl.io'
+
+      - name: Update release packages
+        if: env.VERSION != ''
+        run: runuser -u builder -- packaging/aur/update.sh "${VERSION#v}"
+
+      - name: Refresh the -git metadata
+        if: env.VERSION == ''
+        working-directory: packaging/aur/proton-drive-for-linux-git
+        run: runuser -u builder -- sh -c 'makepkg --printsrcinfo > .SRCINFO'
+
+      - name: Publish to the AUR
+        run: |
+          if [ -n "$VERSION" ]; then
+            runuser -u builder -- packaging/aur/push.sh
+          else
+            runuser -u builder -- packaging/aur/push.sh proton-drive-for-linux-git
+          fi
+
+      - name: Commit the updated recipes to main
+        if: env.VERSION != ''
+        run: |
+          runuser -u builder -- git add packaging/aur
+          if ! runuser -u builder -- git diff --cached --quiet; then
+            runuser -u builder -- git commit -m "chore(aur): update packages to ${VERSION#v}"
+            runuser -u builder -- git push origin HEAD:main
+          fi

.github/workflows/release.yml

@@ -202,3 +202,13 @@ jobs:
           prerelease: false
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+  aur:
+    name: Publish AUR packages
+    needs: build-release
+    if: startsWith(github.ref, 'refs/tags/')
+    uses: ./.github/workflows/aur.yml
+    with:
+      version: ${{ github.ref_name }}
+    secrets:
+      AUR_SSH_PRIVATE_KEY: ${{ secrets.AUR_SSH_PRIVATE_KEY }}

packaging/aur/README.md

@@ -21,6 +21,22 @@ built packages never reach the AUR.
 
 ## Releasing a new version
 
+`.github/workflows/aur.yml` does this automatically:
+
+- **On a release tag**, `release.yml` calls it after the GitHub release is
+  published. It runs `./update.sh <version>`, pushes all three packages with
+  `./push.sh`, and commits the updated recipes back to `main` as
+  `chore(aur): update packages to <version>`.
+- **On a push to `main` that changes `proton-drive-for-linux-git/`**, it
+  regenerates that package's `.SRCINFO` and pushes only the -git package.
+- **By hand**, run the workflow from the Actions tab. Give a version to publish
+  a release, or leave it empty to publish only the -git package.
+
+It needs the `AUR_SSH_PRIVATE_KEY` repository secret: a private key whose public
+half is registered with the AUR account.
+
+To do the same by hand:
+
 1. Tag and publish the upstream release, so the source tarball and the
    `proton-drive-linux-<version>-x86_64.tar.gz` release asset exist.
 2. Run `./update.sh <version>` — it rewrites `pkgver`, resets `pkgrel=1`,
@@ -32,7 +48,8 @@ built packages never reach the AUR.
    for a single package).
 
 `proton-drive-for-linux-git` carries a `pkgver()` function, so its `pkgver` is
-computed at build time; do not push a commit that only bumps it.
+computed at build time; do not push a commit that only bumps it. This is why new
+commits on `main` do not trigger an AUR push.
 
 ## Requirements for pushing