From 8959ac06acb65b7090b2396891c90ea1da23c830 Mon Sep 17 00:00:00 2001
From: Tom Foster <tom@tcpip.uk>
Date: Mon, 22 Sep 2025 17:05:21 +0100
Subject: [PATCH] ci: Split Rust build cache into dependencies and incremental
 caches

Replace single large build cache with separate dependencies and incremental
caches. Dependencies cache survives source code changes and uses tiered
restore keys. Removes build directory from caching to improve CI performance
while maintaining effective compilation caching with sccache.
---
 .forgejo/actions/setup-rust/action.yml | 31 ++++++++++++++++++--------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/.forgejo/actions/setup-rust/action.yml b/.forgejo/actions/setup-rust/action.yml
index d1a070a5..4640f581 100644
--- a/.forgejo/actions/setup-rust/action.yml
+++ b/.forgejo/actions/setup-rust/action.yml
@@ -92,23 +92,36 @@ runs:
     - name: Setup sccache
       uses: https://git.tomfos.tr/tom/sccache-action@v1
 
-    - name: Cache build artifacts
-      id: build-cache
+    - name: Cache dependencies
+      id: deps-cache
       uses: actions/cache@v4
       with:
         path: |
-          target/**/deps
-          !target/**/deps/*.rlib
-          target/**/build
           target/**/.fingerprint
-          target/**/incremental
+          target/**/deps
           target/**/*.d
+          target/**/.cargo-lock
+          target/**/CACHEDIR.TAG
+          target/**/.rustc_info.json
           /timelord/
-        # Build artifacts - cache per code change, restore from deps when code changes
+        # Dependencies cache - based on Cargo.lock, survives source code changes
         key: >-
-          continuwuity-build-${{ steps.runner-os.outputs.slug }}-${{ steps.runner-os.outputs.arch }}-${{ inputs.rust-version }}${{ inputs.cache-key-suffix && format('-{0}', inputs.cache-key-suffix) || '' }}-${{ hashFiles('rust-toolchain.toml', '**/Cargo.lock') }}-${{ hashFiles('**/*.rs', '**/Cargo.toml') }}
+          continuwuity-deps-${{ steps.runner-os.outputs.slug }}-${{ steps.runner-os.outputs.arch }}-${{ inputs.rust-version }}${{ inputs.cache-key-suffix && format('-{0}', inputs.cache-key-suffix) || '' }}-${{ hashFiles('rust-toolchain.toml', '**/Cargo.lock') }}
         restore-keys: |
-          continuwuity-build-${{ steps.runner-os.outputs.slug }}-${{ steps.runner-os.outputs.arch }}-${{ inputs.rust-version }}${{ inputs.cache-key-suffix && format('-{0}', inputs.cache-key-suffix) || '' }}-${{ hashFiles('rust-toolchain.toml', '**/Cargo.lock') }}-
+          continuwuity-deps-${{ steps.runner-os.outputs.slug }}-${{ steps.runner-os.outputs.arch }}-${{ inputs.rust-version }}${{ inputs.cache-key-suffix && format('-{0}', inputs.cache-key-suffix) || '' }}-
+
+    - name: Cache incremental compilation
+      id: incremental-cache
+      uses: actions/cache@v4
+      with:
+        path: |
+          target/**/incremental
+        # Incremental cache - based on source code changes
+        key: >-
+          continuwuity-incremental-${{ steps.runner-os.outputs.slug }}-${{ steps.runner-os.outputs.arch }}-${{ inputs.rust-version }}${{ inputs.cache-key-suffix && format('-{0}', inputs.cache-key-suffix) || '' }}-${{ hashFiles('rust-toolchain.toml', '**/Cargo.lock') }}-${{ hashFiles('**/*.rs', '**/Cargo.toml') }}
+        restore-keys: |
+          continuwuity-incremental-${{ steps.runner-os.outputs.slug }}-${{ steps.runner-os.outputs.arch }}-${{ inputs.rust-version }}${{ inputs.cache-key-suffix && format('-{0}', inputs.cache-key-suffix) || '' }}-${{ hashFiles('rust-toolchain.toml', '**/Cargo.lock') }}-
+          continuwuity-incremental-${{ steps.runner-os.outputs.slug }}-${{ steps.runner-os.outputs.arch }}-${{ inputs.rust-version }}${{ inputs.cache-key-suffix && format('-{0}', inputs.cache-key-suffix) || '' }}-
 
     - name: End cache restore group
       shell: bash