chore: add golangci-lint, GitHub Actions CI, and pre-commit hooks

Adds .golangci.yml (errcheck, govet, staticcheck, revive, gocyclo,
gocritic, nilerr, errorlint, etc.). Fixes all lint issues found:
- RpcError/wrapRpc renamed to RPCError/wrapRPC (revive var-naming)
- Shadow vars resolved in process.go, outline.go, project.go
- nilerr suppressed with justifying comments in git/collect.go and
  auto/detector.go (WalkDir / intentional empty-returns)
- if-else chain rewritten as switch in format.go (gocritic)
- gofmt applied to detector.go and client.go

Adds .github/workflows/ci.yml: lint (ubuntu), build+vet+test matrix
(ubuntu/windows/macos), and Roslyn helper build (windows). Validated
with actionlint (0 issues).

Adds .githooks/pre-commit + pre-commit.ps1 for local pre-commit checks.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.githooks/pre-commit

@@ -0,0 +1,36 @@
+#!/bin/sh
+# ctx pre-commit hook — shell entry point (works in Git Bash on Windows)
+# Delegates to pre-commit.ps1 on Windows, runs natively on Linux/macOS.
+#
+# To activate:
+#   git config core.hooksPath .githooks
+
+set -e
+
+if command -v powershell.exe >/dev/null 2>&1; then
+  # Windows: delegate to PowerShell script
+  exec powershell.exe -ExecutionPolicy Bypass -File .githooks/pre-commit.ps1
+fi
+
+# Linux / macOS: run directly
+echo "Running gofmt..."
+unformatted=$(gofmt -l .)
+if [ -n "$unformatted" ]; then
+  echo "Files not formatted with gofmt:"
+  echo "$unformatted"
+  echo
+  echo "Run: gofmt -w ."
+  exit 1
+fi
+
+echo "Running go vet..."
+go vet ./...
+
+if command -v golangci-lint >/dev/null 2>&1; then
+  echo "Running golangci-lint..."
+  golangci-lint run ./...
+else
+  echo "warning: golangci-lint not installed, skipping"
+fi
+
+echo "pre-commit checks passed"

.githooks/pre-commit.ps1

@@ -0,0 +1,25 @@
+# ctx pre-commit hook (PowerShell)
+# To activate: git config core.hooksPath .githooks
+$ErrorActionPreference = "Stop"
+
+Write-Host "Running gofmt..."
+$unformatted = gofmt -l .
+if ($unformatted) {
+    Write-Host "Files not formatted with gofmt:"
+    Write-Host $unformatted
+    Write-Host ""
+    Write-Host "Run: gofmt -w ."
+    exit 1
+}
+
+Write-Host "Running go vet..."
+go vet ./...
+
+if (Get-Command golangci-lint -ErrorAction SilentlyContinue) {
+    Write-Host "Running golangci-lint..."
+    golangci-lint run ./...
+} else {
+    Write-Host "warning: golangci-lint not installed, skipping"
+}
+
+Write-Host "pre-commit checks passed"

.github/workflows/ci.yml

@@ -0,0 +1,55 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version: "1.26"
+          cache: true
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v6
+        with:
+          version: latest
+
+  build:
+    name: Build & Test
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version: "1.26"
+          cache: true
+      - name: Build
+        run: go build -v ./...
+      - name: Vet
+        run: go vet ./...
+      - name: Test
+        run: go test -v -race -count=1 ./...
+
+  build-helper:
+    name: Build Roslyn Helper
+    runs-on: windows-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: "10.0.x"
+      - name: Build helper
+        working-directory: tools/roslyn-helper
+        run: dotnet build src/RoslynHelper -c Release

.golangci.yml

@@ -0,0 +1,69 @@
+run:
+  timeout: 3m
+  tests: true
+  go: "1.26"
+
+output:
+  formats:
+    - format: colored-line-number
+  print-issued-lines: true
+  print-linter-name: true
+  sort-results: true
+
+linters:
+  disable-all: true
+  enable:
+    - errcheck       # unhandled errors
+    - govet          # official compiler checks
+    - ineffassign    # useless assignments
+    - staticcheck    # bugs and simplifications
+    - unused         # dead code
+    - gofmt          # formatting
+    - goimports      # import organization
+    - misspell       # typos in strings/comments
+    - revive         # golint successor
+    - gocyclo        # high cyclomatic complexity
+    - gocritic       # additional checks
+    - bodyclose      # http.Response.Body closed
+    - nilerr         # returning nil when err intended
+    - errorlint      # non-wrappable errors
+
+linters-settings:
+  gocyclo:
+    min-complexity: 15
+  govet:
+    enable-all: true
+    disable:
+      - fieldalignment   # unnecessary noise
+  revive:
+    rules:
+      - name: var-naming
+      - name: exported
+        arguments: ["disableStutteringCheck"]  # allows ctx.Context
+      - name: error-return
+      - name: error-naming
+      - name: unexported-return
+      - name: indent-error-flow
+      - name: unreachable-code
+
+issues:
+  exclude-dirs:
+    - tools/roslyn-helper  # C# code, ignore
+    - vendor
+    - bin
+  exclude-rules:
+    # Allow errcheck in cobra command handlers — cobra's RunE owns error printing
+    - path: cmd/
+      linters: [errcheck]
+    # Allow higher complexity in plugin format functions (inherently procedural)
+    - path: internal/plugins/.*/format\.go
+      linters: [gocyclo]
+      text: "cyclomatic complexity"
+    # Allow higher complexity in plugin collect/detect logic
+    - path: internal/plugins/.*/detect
+      linters: [gocyclo]
+      text: "cyclomatic complexity"
+
+  max-issues-per-linter: 0
+  max-same-issues: 0
+  new: false

README.md

@@ -80,6 +80,36 @@ runtime into the Go binary.
 
 See `docs/DECISIONS.md` for the full rationale behind each architectural choice.
 
+## Development
+
+### Prerequisites
+- Go 1.26+
+- .NET SDK 10.0+ (for Roslyn helper)
+- golangci-lint (`go install github.com/golangci/golangci-lint/cmd/golangci-lint@latest`)
+
+### Build
+```sh
+go build -o ctx.exe ./cmd/ctx
+```
+
+### Tests & lint
+```sh
+go vet ./...
+golangci-lint run ./...
+```
+
+### Pre-commit hooks
+```sh
+git config core.hooksPath .githooks
+# On Linux/macOS also: chmod +x .githooks/pre-commit
+```
+
+### Roslyn helper
+```sh
+cd tools/roslyn-helper
+dotnet publish src/RoslynHelper -c Release -r win-x64 --self-contained false -o publish/
+```
+
 ## Contributing
 
 Contributions welcome. See `CONTRIBUTING.md` (coming soon) for guidelines.

internal/plugins/auto/detector.go

@@ -46,8 +46,8 @@ var skipDirs = map[string]bool{
 
 // findings holds raw evidence gathered during the directory walk.
 type findings struct {
-	slnFiles     []string  // forward-slash relative paths to .sln files
+	slnFiles      []string // forward-slash relative paths to .sln files
-	csprojFiles  []string  // forward-slash relative paths to .csproj/.fsproj/.vbproj files
+	csprojFiles   []string // forward-slash relative paths to .csproj/.fsproj/.vbproj files
 	hasGlobalJSON bool
 	packageJSONs  []pkgJSON
 	hasGoModRoot  bool // go.mod is a direct child of rootDir (depth 1)
@@ -68,7 +68,7 @@ func scanDir(rootDir string, maxDepth int) (findings, error) {
 
 	err := filepath.WalkDir(rootDir, func(path string, d fs.DirEntry, err error) error {
 		if err != nil {
-			return nil // skip unreadable entries silently
+			return nil //nolint:nilerr // skip unreadable entries; returning err would abort the walk
 		}
 		if path == rootDir {
 			return nil // skip root itself

internal/plugins/csharp/format.go

@@ -223,13 +223,14 @@ func writeMultiTargeting(w io.Writer, projects []helper.ProjectInfo) {
 
 	if len(frameworkSets) == 0 {
 		// All same framework, or single framework each
-		if len(allFrameworks) == 1 {
+		switch len(allFrameworks) {
+		case 0:
+			fmt.Fprintf(w, "No target frameworks detected.\n\n")
+		case 1:
 			for tf := range allFrameworks {
 				fmt.Fprintf(w, "None — all projects target `%s`.\n\n", tf)
 			}
-		} else if len(allFrameworks) == 0 {
+		default:
-			fmt.Fprintf(w, "No target frameworks detected.\n\n")
-		} else {
 			// Multiple different single targets
 			for _, p := range projects {
 				if len(p.TargetFrameworks) > 0 {

internal/plugins/csharp/helper/client.go

@@ -84,7 +84,7 @@ type PackageReference struct {
 func (c *Client) Ping() (*PingResult, error) {
 	raw, err := c.proc.Send("ping", nil)
 	if err != nil {
-		return nil, wrapRpc("ping", err)
+		return nil, wrapRPC("ping", err)
 	}
 	var r PingResult
 	if err := json.Unmarshal(raw, &r); err != nil {
@@ -98,7 +98,7 @@ func (c *Client) LoadSolution(path string) (*LoadSolutionResult, error) {
 	params := map[string]string{"path": path}
 	raw, err := c.proc.Send("loadSolution", params)
 	if err != nil {
-		return nil, wrapRpc("loadSolution", err)
+		return nil, wrapRPC("loadSolution", err)
 	}
 	var r LoadSolutionResult
 	if err := json.Unmarshal(raw, &r); err != nil {
@@ -111,7 +111,7 @@ func (c *Client) LoadSolution(path string) (*LoadSolutionResult, error) {
 func (c *Client) ProjectSummary() (*ProjectSummary, error) {
 	raw, err := c.proc.Send("projectSummary", nil)
 	if err != nil {
-		return nil, wrapRpc("projectSummary", err)
+		return nil, wrapRPC("projectSummary", err)
 	}
 	var r ProjectSummary
 	if err := json.Unmarshal(raw, &r); err != nil {
@@ -124,12 +124,12 @@ func (c *Client) ProjectSummary() (*ProjectSummary, error) {
 
 // OutlineResult is the structural outline of a single .cs file.
 type OutlineResult struct {
-	Path           string        `json:"path"`
+	Path            string        `json:"path"`
-	Namespace      string        `json:"namespace"`
+	Namespace       string        `json:"namespace"`
-	LineCount      int           `json:"lineCount"`
+	LineCount       int           `json:"lineCount"`
-	Usings         []string      `json:"usings"`
+	Usings          []string      `json:"usings"`
-	Types          []OutlineType `json:"types"`
+	Types           []OutlineType `json:"types"`
-	HasSyntaxErrors bool         `json:"hasSyntaxErrors"`
+	HasSyntaxErrors bool          `json:"hasSyntaxErrors"`
 }
 
 // OutlineType describes a type (class, interface, struct, record, enum) in the file.
@@ -157,7 +157,7 @@ func (c *Client) Outline(path string) (*OutlineResult, error) {
 	params := map[string]string{"path": path}
 	raw, err := c.proc.Send("outline", params)
 	if err != nil {
-		return nil, wrapRpc("outline", err)
+		return nil, wrapRPC("outline", err)
 	}
 	var r OutlineResult
 	if err := json.Unmarshal(raw, &r); err != nil {
@@ -166,9 +166,9 @@ func (c *Client) Outline(path string) (*OutlineResult, error) {
 	return &r, nil
 }
 
-// wrapRpc wraps RpcError values into user-friendly messages.
+// wrapRPC wraps RPCError values into user-friendly messages.
-func wrapRpc(method string, err error) error {
+func wrapRPC(method string, err error) error {
-	var rpcErr *RpcError
+	var rpcErr *RPCError
 	if errors.As(err, &rpcErr) {
 		switch rpcErr.Code {
 		case "E_NOT_FOUND":

internal/plugins/csharp/helper/process.go

@@ -73,8 +73,8 @@ func (p *Process) Send(method string, params interface{}) (json.RawMessage, erro
 	}
 	line = append(line, '\n')
 
-	if _, err := p.stdin.Write(line); err != nil {
+	if _, werr := p.stdin.Write(line); werr != nil {
-		return nil, fmt.Errorf("helper write (process may have crashed): %w", err)
+		return nil, fmt.Errorf("helper write (process may have crashed): %w", werr)
 	}
 
 	respLine, err := p.stdout.ReadString('\n')

internal/plugins/csharp/helper/protocol.go

@@ -13,14 +13,14 @@ type Request struct {
 type Response struct {
 	ID     int             `json:"id"`
 	Result json.RawMessage `json:"result,omitempty"`
-	Error  *RpcError       `json:"error,omitempty"`
+	Error  *RPCError       `json:"error,omitempty"`
 }
 
 // RpcError is a structured error from the helper process.
-type RpcError struct {
+type RPCError struct {
 	Code    string          `json:"code"`
 	Message string          `json:"message"`
 	Data    json.RawMessage `json:"data,omitempty"`
 }
 
-func (e *RpcError) Error() string { return e.Code + ": " + e.Message }
+func (e *RPCError) Error() string { return e.Code + ": " + e.Message }

internal/plugins/csharp/outline.go

@@ -39,7 +39,7 @@ func runOutline(ctx *core.Context, file string) error {
 		return errExit
 	}
 
-	if _, err := os.Stat(abs); err != nil {
+	if _, statErr := os.Stat(abs); statErr != nil {
 		fmt.Fprintf(ctx.Stderr, "file not found: %s\n", abs)
 		return errExit
 	}

internal/plugins/csharp/project.go

@@ -44,8 +44,8 @@ func runProject(ctx *core.Context) error {
 	}
 	defer client.Close()
 
-	if _, err := client.LoadSolution(slnPath); err != nil {
+	if _, loadErr := client.LoadSolution(slnPath); loadErr != nil {
-		fmt.Fprintln(ctx.Stderr, err.Error())
+		fmt.Fprintln(ctx.Stderr, loadErr.Error())
 		return errExit
 	}
 

internal/plugins/git/collect.go

@@ -171,8 +171,8 @@ func collectRepoInfo(dir string) (repoInfo, error) {
 func collectCommits(dir string, n int) ([]commit, error) {
 	out, err := gitCmd(dir, "log", fmt.Sprintf("-n%d", n), "--pretty=format:%h|%at|%an|%s")
 	if err != nil || out == "" {
-		// Empty repo or no commits — not a hard error.
+		// Empty repo or no commits — not an error for our purposes.
-		return nil, nil
+		return nil, nil //nolint:nilerr // intentional: git failures here mean "nothing to show"
 	}
 	var commits []commit
 	for _, line := range strings.Split(out, "\n") {
@@ -254,7 +254,7 @@ func parseNumstat(dir string, cached bool) ([]fileChange, error) {
 	}
 	out, err := gitCmd(dir, args...)
 	if err != nil || out == "" {
-		return nil, nil
+		return nil, nil //nolint:nilerr // no changes or not in a git repo — not an error
 	}
 	var changes []fileChange
 	for _, line := range strings.Split(out, "\n") {
@@ -280,7 +280,7 @@ func parseNumstat(dir string, cached bool) ([]fileChange, error) {
 func parseUntracked(dir string) ([]string, error) {
 	out, err := gitCmd(dir, "status", "--porcelain=v1")
 	if err != nil || out == "" {
-		return nil, nil
+		return nil, nil //nolint:nilerr // clean working tree or not in a git repo — not an error
 	}
 	var untracked []string
 	for _, line := range strings.Split(out, "\n") {