bootc-ubuntu-setup: Add support for ubuntu-26.04 runners

Ubuntu 26.04 ships a sufficiently modern podman (with heredoc support
and no manifest handling bugs), so unlike 24.04 we can skip the plucky
PPA and package upgrade path entirely. This simplifies the setup on
26.04 to just installing `just`.

The version gate is refactored from a hard `test` assertion into a
`case` statement that dispatches per-version setup logic and rejects
unsupported runners with a clear error.

CI test jobs are added for ubuntu-26.04 in both PR and published-action
workflows. The PR test includes a heredoc Containerfile build to verify
the native podman meets the minimum capability bar per the acceptance
criteria.

Closes: #49

Assisted-by: Claude Code (Claude Opus 4)
Signed-off-by: Colin Walters <walters@verbum.org>

Author: redhat-chai-bot

.github/workflows/test-actions-pr.yml

@@ -24,6 +24,37 @@ jobs:
           just --version
           test -n "$ARCH"
 
+  test-bootc-ubuntu-setup-2604:
+    name: Test bootc-ubuntu-setup (26.04)
+    runs-on: ubuntu-26.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      - name: Run bootc-ubuntu-setup
+        uses: ./bootc-ubuntu-setup
+
+      - name: Verify setup
+        run: |
+          podman --version
+          just --version
+          test -n "$ARCH"
+
+      - name: Verify podman heredoc support
+        shell: bash
+        run: |
+          set -euo pipefail
+          dir=$(mktemp -d)
+          cat > "${dir}/Containerfile" <<'CEOF'
+          FROM docker.io/library/alpine:latest
+          RUN <<EOF
+          echo "heredoc works" > /heredoc-test.txt
+          EOF
+          CEOF
+          podman build -t localhost/heredoc-test:latest -f "${dir}/Containerfile" "${dir}"
+          result="$(podman run --rm localhost/heredoc-test:latest cat /heredoc-test.txt)"
+          test "${result}" = "heredoc works"
+
   test-setup-rust:
     name: Test setup-rust
     runs-on: ubuntu-latest

.github/workflows/test-actions-published.yml

@@ -21,6 +21,19 @@ jobs:
           just --version
           test -n "$ARCH"
 
+  test-bootc-ubuntu-setup-2604:
+    name: Test bootc-ubuntu-setup@main (26.04)
+    runs-on: ubuntu-26.04
+    steps:
+      - name: Run bootc-ubuntu-setup
+        uses: bootc-dev/actions/bootc-ubuntu-setup@main
+
+      - name: Verify setup
+        run: |
+          podman --version
+          just --version
+          test -n "$ARCH"
+
   test-setup-rust:
     name: Test setup-rust@main
     runs-on: ubuntu-latest

bootc-ubuntu-setup/action.yml

@@ -39,27 +39,41 @@ runs:
           fi
         done
     # We really want support for heredocs
-    - name: Update podman and install just
+    - name: Install required packages
       shell: bash
       run: |
         set -eux
-        # Require the runner is ubuntu-24.04
         IDV=$(. /usr/lib/os-release && echo ${ID}-${VERSION_ID})
-        test "${IDV}" = "ubuntu-24.04"
-        # plucky is the next release. The azure.archive.ubuntu.com mirror only carries amd64.
-        # Other architectures like arm64 use ports.ubuntu.com/ubuntu-ports.
-        if [ "$(dpkg --print-architecture)" = "amd64" ]; then
-          mirror="http://azure.archive.ubuntu.com/ubuntu"
-        else
-          mirror="http://ports.ubuntu.com/ubuntu-ports"
-        fi
-        echo "deb ${mirror} plucky universe main" | sudo tee /etc/apt/sources.list.d/plucky.list
-        # apt has a compiled-in default of 3 retries with exponential backoff (1s, 2s, 4s),
-        # capped at 30s per attempt. 34 retries covers ~15 min of cumulative delay; use 35.
-        echo 'Acquire::Retries "35";' | sudo tee /etc/apt/apt.conf.d/80-retries
-        /bin/time -f '%E %C' sudo apt update
-        # skopeo is currently older in plucky for some reason hence --allow-downgrades
-        /bin/time -f '%E %C' sudo apt install -y --allow-downgrades crun/plucky buildah/plucky podman/plucky skopeo/plucky just
+        case "${IDV}" in
+          ubuntu-24.04)
+            # 24.04's podman is too old (no heredoc support, manifest bugs);
+            # pull newer packages from plucky (25.04).
+            # The azure.archive.ubuntu.com mirror only carries amd64.
+            # Other architectures like arm64 use ports.ubuntu.com/ubuntu-ports.
+            if [ "$(dpkg --print-architecture)" = "amd64" ]; then
+              mirror="http://azure.archive.ubuntu.com/ubuntu"
+            else
+              mirror="http://ports.ubuntu.com/ubuntu-ports"
+            fi
+            echo "deb ${mirror} plucky universe main" | sudo tee /etc/apt/sources.list.d/plucky.list
+            # apt has a compiled-in default of 3 retries with exponential backoff (1s, 2s, 4s),
+            # capped at 30s per attempt. 34 retries covers ~15 min of cumulative delay; use 35.
+            echo 'Acquire::Retries "35";' | sudo tee /etc/apt/apt.conf.d/80-retries
+            /bin/time -f '%E %C' sudo apt update
+            # skopeo is currently older in plucky for some reason hence --allow-downgrades
+            /bin/time -f '%E %C' sudo apt install -y --allow-downgrades crun/plucky buildah/plucky podman/plucky skopeo/plucky just
+            ;;
+          ubuntu-26.04)
+            # 26.04 ships a sufficiently modern podman with heredoc support;
+            # no PPA or package upgrades needed — just install extras.
+            /bin/time -f '%E %C' sudo apt update
+            /bin/time -f '%E %C' sudo apt install -y just
+            ;;
+          *)
+            echo "Unsupported runner: ${IDV}" >&2
+            exit 1
+            ;;
+        esac
     # This is the default on e.g. Fedora derivatives, but not Debian.
     # Only needed when libvirt/virtualization is requested.
     - name: Enable unprivileged /dev/kvm access