chore: Use correct commit hash as github cache key if submodule is not checked out (#107)

* chore: Use correct commit hash as github cache key

* chore: Clone with submodules

This will also initialize all the "doc" submodules, which might prove
too much.

Author: I-Al-Istannen

.github/workflows/enzyme-ci.yml

@@ -24,11 +24,12 @@ jobs:
       - name: Checkout Rust source
         uses: actions/checkout@v4
         with:
+          submodules: true # check out all submodules so the cache can work correctly
           fetch-depth: 2
       - uses: dtolnay/rust-toolchain@nightly
       - name: Get LLVM commit hash
         id: llvm-commit
-        run: echo "HEAD=$(git -C src/llvm-project rev-parse HEAD)" >> $GITHUB_OUTPUT
+        run: echo "HEAD=$(git rev-parse HEAD:src/llvm-project)" >> $GITHUB_OUTPUT
       - name: Cache LLVM
         id: cache-llvm
         uses: actions/cache@v4
@@ -37,7 +38,7 @@ jobs:
           key: ${{ matrix.os }}-llvm-${{ steps.llvm-commit.outputs.HEAD }}
       - name: Get Enzyme commit hash
         id: enzyme-commit
-        run: echo "HEAD=$(git -C src/tools/enzyme rev-parse HEAD)" >> $GITHUB_OUTPUT
+        run: echo "HEAD=$(git rev-parse HEAD:src/tools/enzyme)" >> $GITHUB_OUTPUT
       - name: Cache Enzyme
         id: cache-enzyme
         uses: actions/cache@v4