feat: Implement ability to disable adding job ID + rust environment hashes to cache names (#279)

README.md

@@ -28,6 +28,16 @@ sensible defaults.
     # default: empty
     key: ""
 
+    # If the automatic `job`-based cache key should include the job id.
+    # default: "true"
+    add-job-id-key: ""
+
+    # Weather the a hash of the rust environment should be included in the cache key.
+    # This includes a hash of all Cargo.toml/Cargo.lock files, rust-toolchain files,
+    # and .cargo/config.toml files (if present), as well as the specified 'env-vars'.
+    # default: "true"
+    add-rust-environment-hash-key: ""
+
     # A whitespace separated list of env-var *prefixes* who's value contributes
     # to the environment cache key.
     # The env-vars are matched by *prefix*, so the default `RUST` var will
@@ -121,12 +131,14 @@ This action currently caches the following files/directories:
 
 This cache is automatically keyed by:
 
-- the github [`job_id`](https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_id),
+- the github [`job_id`](https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_id)
+(if `add-job-id-key` is `"true"`),
 - the rustc release / host / hash,
-- the value of some compiler-specific environment variables (eg. RUSTFLAGS, etc), and
-- a hash of all `Cargo.lock` / `Cargo.toml` files found anywhere in the repository (if present).
-- a hash of all `rust-toolchain` / `rust-toolchain.toml` files in the root of the repository (if present).
-- a hash of all `.cargo/config.toml` files in the root of the repository (if present).
+- the following values, if `add-rust-environment-hash-key` is `"true"`:
+  - the value of some compiler-specific environment variables (eg. RUSTFLAGS, etc), and
+  - a hash of all `Cargo.lock` / `Cargo.toml` files found anywhere in the repository (if present).
+  - a hash of all `rust-toolchain` / `rust-toolchain.toml` files in the root of the repository (if present).
+  - a hash of all `.cargo/config.toml` files in the root of the repository (if present).
 
 An additional input `key` can be provided if the builtin keys are not sufficient.