internal/ci: make our checkout step configurable

This prepares for a later change in another repository where we need to
configure that submodules are checked out.

We could also consider having submodules checkout being the default.

This change should not result in any .github/workflows changes.

Signed-off-by: Paul Jolly <paul@myitcv.io>
Change-Id: I00d8b8238a832054bda4a883fd2d53a0090e5623
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/551531
Unity-Result: CUEcueckoo <cueckoo@cuelang.org>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>

internal/ci/base/base.cue

@@ -49,8 +49,8 @@ import (
 	}
 }
 
-#checkoutCode: [
-	json.#step & {
+#checkoutCode: {
+	#actionsCheckout: json.#step & {
 		name: "Checkout code"
 		uses: "actions/checkout@v3"
 
@@ -63,25 +63,29 @@ import (
 			ref:           "${{ github.event.pull_request.head.sha }}"
 			"fetch-depth": 0 // see the docs below
 		}
-	},
-	// Restore modified times to work around https://go.dev/issues/58571,
-	// as otherwise we would get lots of unnecessary Go test cache misses.
-	// Note that this action requires actions/checkout to use a fetch-depth of 0.
-	// Since this is a third-party action which runs arbitrary code,
-	// we pin a commit hash for v2 to be in control of code updates.
-	// Also note that git-restore-mtime does not update all directories,
-	// per the bug report at https://github.com/MestreLion/git-tools/issues/47,
-	// so we first reset all directory timestamps to a static time as a fallback.
-	// TODO(mvdan): May be unnecessary once the Go bug above is fixed.
-	json.#step & {
-		name: "Reset git directory modification times"
-		run:  "touch -t 202211302355 $(find * -type d)"
-	},
-	json.#step & {
-		name: "Restore git file modification times"
-		uses: "chetan/git-restore-mtime-action@075f9bc9d159805603419d50f794bd9f33252ebe"
-	},
-]
+	}
+
+	[
+		#actionsCheckout,
+		// Restore modified times to work around https://go.dev/issues/58571,
+		// as otherwise we would get lots of unnecessary Go test cache misses.
+		// Note that this action requires actions/checkout to use a fetch-depth of 0.
+		// Since this is a third-party action which runs arbitrary code,
+		// we pin a commit hash for v2 to be in control of code updates.
+		// Also note that git-restore-mtime does not update all directories,
+		// per the bug report at https://github.com/MestreLion/git-tools/issues/47,
+		// so we first reset all directory timestamps to a static time as a fallback.
+		// TODO(mvdan): May be unnecessary once the Go bug above is fixed.
+		json.#step & {
+			name: "Reset git directory modification times"
+			run:  "touch -t 202211302355 $(find * -type d)"
+		},
+		json.#step & {
+			name: "Restore git file modification times"
+			uses: "chetan/git-restore-mtime-action@075f9bc9d159805603419d50f794bd9f33252ebe"
+		},
+	]
+}
 
 #earlyChecks: json.#step & {
 	name: "Early git and code sanity checks"