Use a dev drive for testing on Windows

.github/workflows/ci.yaml

@@ -321,14 +321,30 @@ jobs:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
           persist-credentials: false
+      - name: Setup Dev Drive
+        run: ${{ github.workspace }}/.github/workflows/setup-dev-drive.ps1
+
+      # actions/checkout does not let us clone into anywhere outside `github.workspace`, so we have to copy the clone
+      # the fuzz corpus links are broken so we remove them
+      - name: Copy Git Repo to Dev Drive
+        run: |
+          Remove-Item -Path ".\fuzz\corpus" -Recurse
+          Copy-Item -Path "${{ github.workspace }}" -Destination "${{ env.RUFF_WORKSPACE }}" -Recurse
+
       - uses: Swatinem/rust-cache@9d47c6ad4b02e050fd481d890b2ea34778fd09d6 # v2.7.8
+        with:
+          workspaces: ${{ env.RUFF_WORKSPACE }}
+
       - name: "Install Rust toolchain"
+        working-directory: ${{ env.RUFF_WORKSPACE }}
         run: rustup show
+
       - name: "Install cargo nextest"
         uses: taiki-e/install-action@d12e869b89167df346dd0ff65da342d1fb1202fb # v2.53.2
         with:
           tool: cargo-nextest
       - name: "Run tests"
+        working-directory: ${{ env.RUFF_WORKSPACE }}
         shell: bash
         env:
           NEXTEST_PROFILE: "ci"

.github/workflows/setup-dev-drive.ps1

@@ -0,0 +1,62 @@
+# Configures a drive for testing in CI.
+
+# When not using a GitHub Actions "larger runner", the `D:` drive is present and
+# has similar or better performance characteristics than a ReFS dev drive.
+# Sometimes using a larger runner is still more performant (e.g., when running
+# the test suite) and we need to create a dev drive. This script automatically
+# configures the appropriate drive.
+
+# Note we use `Get-PSDrive` is not sufficient because the drive letter is assigned.
+if (Test-Path "D:\") {
+    Write-Output "Using existing drive at D:"
+    $Drive = "D:"
+} else {
+	# The size (20 GB) is chosen empirically to be large enough for our
+	# workflows; larger drives can take longer to set up.
+	$Volume = New-VHD -Path C:/ruff_dev_drive.vhdx -SizeBytes 20GB |
+						Mount-VHD -Passthru |
+						Initialize-Disk -Passthru |
+						New-Partition -AssignDriveLetter -UseMaximumSize |
+						Format-Volume -DevDrive -Confirm:$false -Force
+
+	$Drive = "$($Volume.DriveLetter):"
+
+	# Set the drive as trusted
+	# See https://learn.microsoft.com/en-us/windows/dev-drive/#how-do-i-designate-a-dev-drive-as-trusted
+	fsutil devdrv trust $Drive
+
+	# Disable antivirus filtering on dev drives
+	# See https://learn.microsoft.com/en-us/windows/dev-drive/#how-do-i-configure-additional-filters-on-dev-drive
+	fsutil devdrv enable /disallowAv
+
+	# Remount so the changes take effect
+	Dismount-VHD -Path C:/ruff_dev_drive.vhdx
+	Mount-VHD -Path C:/ruff_dev_drive.vhdx
+
+	# Show some debug information
+	Write-Output $Volume
+	fsutil devdrv query $Drive
+
+    Write-Output "Using Dev Drive at $Volume"
+}
+
+$Tmp = "$($Drive)\ruff-tmp"
+
+# Create the directory ahead of time in an attempt to avoid race-conditions
+New-Item $Tmp -ItemType Directory
+
+# Move Cargo to the dev drive
+New-Item -Path "$($Drive)/.cargo/bin" -ItemType Directory -Force
+Copy-Item -Path "C:/Users/runneradmin/.cargo/*" -Destination "$($Drive)/.cargo/" -Recurse -Force
+
+Write-Output `
+	"DEV_DRIVE=$($Drive)" `
+	"TMP=$($Tmp)" `
+	"TEMP=$($Tmp)" `
+	"UV_INTERNAL__TEST_DIR=$($Tmp)" `
+	"RUSTUP_HOME=$($Drive)/.rustup" `
+	"CARGO_HOME=$($Drive)/.cargo" `
+	"RUFF_WORKSPACE=$($Drive)/ruff" `
+	"PATH=$($Drive)/.cargo/bin;$env:PATH" `
+	>> $env:GITHUB_ENV
+