From 8645982dffab25b50f8c6715112722b155bdff24 Mon Sep 17 00:00:00 2001
From: Jason Orendorff <jorendorff@github.com>
Date: Mon, 12 Jun 2023 11:14:05 -0500
Subject: [PATCH] rust-toolchain.toml and incremental build example

Changes to rust-toolchain.toml should invalidate the cache.
Also, add an example with incremental builds.
---
 examples.md | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/examples.md b/examples.md
index 1bcde91..2d26193 100644
--- a/examples.md
+++ b/examples.md
@@ -596,7 +596,26 @@ whenever possible:
       ~/.cargo/registry/cache/
       ~/.cargo/git/db/
       target/
-    key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+    key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock', 'rust-toolchain.toml') }}
+```
+
+Since Rust compile times are so long, you might want to take advantage of incremental builds. To do this, use the configuration below.
+- Include the `run_id` in the key to force `actions/cache` to upload a new snapshot after every build.
+- Use `restore-keys:` to load the previous build (when there are multiple partial matches, it selects the most recent).
+
+```yaml
+- uses: actions/cache@v3
+  with:
+    path: |
+      ~/.cargo/bin/
+      ~/.cargo/registry/index/
+      ~/.cargo/registry/cache/
+      ~/.cargo/git/db/
+      ~/.rustup/
+      target/
+    key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock', 'rust-toolchain.toml') }}-${{ github.run_id }}
+    restore-keys: |
+      ${{ runner.os }}-cargo-${{ hashFiles(**/'Cargo.lock', 'rust-toolchain.toml') }}
 ```
 
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