ci: Add ci-config.toml in .cargo folder. (#3392)

Release Notes:

- N/A

.cargo/ci-config.toml

@@ -0,0 +1,12 @@
+# This config is different from config.toml in this directory, as the latter is recognized by Cargo.
+# This file is placed in $HOME/.cargo/config.toml on CI runs. Cargo then merges Zeds .cargo/config.toml with $HOME/.cargo/config.toml
+# with preference for settings from Zeds config.toml.
+# TL;DR: If a value is set in both ci-config.toml and config.toml, config.toml value takes precedence.
+# Arrays are merged together though. See: https://doc.rust-lang.org/cargo/reference/config.html#hierarchical-structure
+# The intent for this file is to configure CI build process with a divergance from Zed developers experience; for example, in this config file
+# we use `-D warnings` for rustflags (which makes compilation fail in presence of warnings during build process). Placing that in developers `config.toml`
+# would be incovenient.
+# We *could* override things like RUSTFLAGS manually by setting them as environment variables, but that is less DRY; worse yet, if you forget to set proper environment variables
+# in one spot, that's going to trigger a rebuild of all of the artifacts. Using ci-config.toml we can define these overrides for CI in one spot and not worry about it.
+[build]
+rustflags = ["-D", "warnings"]

.github/workflows/ci.yml

@@ -23,15 +23,15 @@ jobs:
       - self-hosted
       - test
     steps:
-      - name: Set up default .cargo/config.toml
-        run: printf "[build]\nrustflags = [\"-D\", \"warnings\"]" > $HOME/.cargo/config.toml
-
       - name: Checkout repo
         uses: actions/checkout@v3
         with:
           clean: false
           submodules: "recursive"
 
+      - name: Set up default .cargo/config.toml
+        run: cp ./.cargo/ci-config.toml ~/.cargo/config.toml
+
       - name: Run rustfmt
         uses: ./.github/actions/check_formatting