ci(e2e): cache the Rust build of the E2E suite bundles

build-e2e-bundles restores a Rust target cache, and Rust Cache saves it
on main, where Branch E2E never runs.

Signed-off-by: Matthew Grossman <mgrossman@nvidia.com>

Author: matthewgrossman

.github/workflows/branch-e2e.yml

@@ -212,7 +212,8 @@ jobs:
   # openshell-conformance, built once per run instead of in every row (see
   # e2e-suites.yml). The rows only run on amd64, so only the x86_64 guest
   # target is built. Each bundle holds its whole family; a row picks its
-  # package at run time.
+  # package at run time. Rust Cache (rust-cache.yml) saves the cache on main;
+  # keep the env and build commands aligned with its e2e-bundles job.
   build-e2e-bundles:
     name: E2E suite bundles (x86_64-unknown-linux-musl)
     needs: [pr_metadata]
@@ -228,11 +229,16 @@ jobs:
           ref: ${{ github.sha }}
       - uses: ./.github/actions/setup-nix
         with:
+          prepare-shell: "true"
           cachix-auth-token: ${{ secrets.CACHIX_AUTH_TOKEN }}
+      - uses: ./.github/actions/setup-rust
+        with:
+          cache-key: e2e-bundles-v1-x86_64-unknown-linux-musl
       - name: Build the bundles
         env:
           # One target directory for every family, so later families reuse
-          # testkit-ready and the dependencies the first one built.
+          # testkit-ready and the dependencies the first one built. It is the
+          # root target directory, which setup-rust caches.
           CARGO_TARGET_DIR: ${{ github.workspace }}/target
           # Every row downloads the bundles. Line tables keep backtraces
           # readable at a third of the size of full debuginfo.

.github/workflows/rust-cache.yml

@@ -3,9 +3,10 @@
 
 name: Rust Cache
 
-# Branch Checks never runs on main, so this saves the rust-checks cache that PR
-# mirrors and merge groups restore. Keep env and build commands aligned with
-# the Branch Checks rust-test job so the cache keys and contents match.
+# Branch Checks and Branch E2E never run on main, so this saves the Rust
+# caches that PR mirrors and merge groups restore. Keep each job's env and
+# build commands aligned with the job that restores its cache, so the cache
+# keys and contents match.
 on:
   push:
     branches:
@@ -65,3 +66,37 @@ jobs:
           cargo nextest run --locked --profile ci --workspace --features openshell-server/test-support --no-run
           cargo nextest run --locked --config-file .config/nextest.toml --profile ci --manifest-path examples/supervisor-middleware-content-guard/Cargo.toml --no-run
           cargo nextest run --locked --config-file .config/nextest.toml --profile ci --manifest-path tests/testkit/Cargo.toml --no-run
+
+  # Restored by build-e2e-bundles in branch-e2e.yml.
+  e2e-bundles:
+    name: E2E suite bundles cache (x86_64-unknown-linux-musl)
+    runs-on: linux-amd64-cpu8
+    timeout-minutes: 60
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+
+      - uses: ./.github/actions/setup-nix
+        with:
+          prepare-shell: "true"
+          cachix-auth-token: ${{ secrets.CACHIX_AUTH_TOKEN }}
+
+      - id: rust
+        uses: ./.github/actions/setup-rust
+        with:
+          cache-key: e2e-bundles-v1-x86_64-unknown-linux-musl
+          save-cache: "true"
+
+      - name: Build the bundles
+        if: steps.rust.outputs.cache-hit != 'true'
+        env:
+          CARGO_TARGET_DIR: ${{ github.workspace }}/target
+          CARGO_PROFILE_DEV_DEBUG: line-tables-only
+        run: |
+          set -euo pipefail
+          nix build --no-link .#openshell-test-runner || nix build --no-link .#openshell-test-runner
+          for family in features drivers/podman; do
+            nix run .#openshell-test-runner -- build \
+              --family "$family" --out "$RUNNER_TEMP/e2e-bundles/${family//\//-}"
+          done