feat: walk up directory tree to find .cheat directory (#602)

Previously cheat only checked the current working directory for a .cheat
subdirectory. Now it walks upward through ancestor directories, stopping
at the first .cheat directory found. This mirrors how git discovers .git
directories, so users can place .cheat at their project root and have it
work from any subdirectory.

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

internal/config/config_test.go

@@ -4,6 +4,7 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"runtime"
 	"testing"
 
 	"github.com/davecgh/go-spew/spew"
@@ -13,9 +14,267 @@ import (
 	"github.com/cheat/cheat/internal/mock"
 )
 
+// TestFindLocalCheatpathInCurrentDir tests that .cheat in the given dir is found
+func TestFindLocalCheatpathInCurrentDir(t *testing.T) {
+	tempDir, err := os.MkdirTemp("", "cheat-test-*")
+	if err != nil {
+		t.Fatalf("failed to create temp dir: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	cheatDir := filepath.Join(tempDir, ".cheat")
+	if err := os.Mkdir(cheatDir, 0755); err != nil {
+		t.Fatalf("failed to create .cheat dir: %v", err)
+	}
+
+	result := findLocalCheatpath(tempDir)
+	if result != cheatDir {
+		t.Errorf("expected %s, got %s", cheatDir, result)
+	}
+}
+
+// TestFindLocalCheatpathInParent tests walking up to a parent directory
+func TestFindLocalCheatpathInParent(t *testing.T) {
+	tempDir, err := os.MkdirTemp("", "cheat-test-*")
+	if err != nil {
+		t.Fatalf("failed to create temp dir: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	cheatDir := filepath.Join(tempDir, ".cheat")
+	if err := os.Mkdir(cheatDir, 0755); err != nil {
+		t.Fatalf("failed to create .cheat dir: %v", err)
+	}
+
+	subDir := filepath.Join(tempDir, "sub")
+	if err := os.Mkdir(subDir, 0755); err != nil {
+		t.Fatalf("failed to create sub dir: %v", err)
+	}
+
+	result := findLocalCheatpath(subDir)
+	if result != cheatDir {
+		t.Errorf("expected %s, got %s", cheatDir, result)
+	}
+}
+
+// TestFindLocalCheatpathInGrandparent tests walking up multiple levels
+func TestFindLocalCheatpathInGrandparent(t *testing.T) {
+	tempDir, err := os.MkdirTemp("", "cheat-test-*")
+	if err != nil {
+		t.Fatalf("failed to create temp dir: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	cheatDir := filepath.Join(tempDir, ".cheat")
+	if err := os.Mkdir(cheatDir, 0755); err != nil {
+		t.Fatalf("failed to create .cheat dir: %v", err)
+	}
+
+	deepDir := filepath.Join(tempDir, "a", "b", "c")
+	if err := os.MkdirAll(deepDir, 0755); err != nil {
+		t.Fatalf("failed to create deep dir: %v", err)
+	}
+
+	result := findLocalCheatpath(deepDir)
+	if result != cheatDir {
+		t.Errorf("expected %s, got %s", cheatDir, result)
+	}
+}
+
+// TestFindLocalCheatpathNearestWins tests that the closest .cheat is returned
+func TestFindLocalCheatpathNearestWins(t *testing.T) {
+	tempDir, err := os.MkdirTemp("", "cheat-test-*")
+	if err != nil {
+		t.Fatalf("failed to create temp dir: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	// Create .cheat at root level
+	if err := os.Mkdir(filepath.Join(tempDir, ".cheat"), 0755); err != nil {
+		t.Fatalf("failed to create root .cheat dir: %v", err)
+	}
+
+	// Create sub/.cheat (the nearer one)
+	subDir := filepath.Join(tempDir, "sub")
+	if err := os.Mkdir(subDir, 0755); err != nil {
+		t.Fatalf("failed to create sub dir: %v", err)
+	}
+	nearCheatDir := filepath.Join(subDir, ".cheat")
+	if err := os.Mkdir(nearCheatDir, 0755); err != nil {
+		t.Fatalf("failed to create sub .cheat dir: %v", err)
+	}
+
+	// Search from sub/deep/
+	deepDir := filepath.Join(subDir, "deep")
+	if err := os.Mkdir(deepDir, 0755); err != nil {
+		t.Fatalf("failed to create deep dir: %v", err)
+	}
+
+	result := findLocalCheatpath(deepDir)
+	if result != nearCheatDir {
+		t.Errorf("expected nearest %s, got %s", nearCheatDir, result)
+	}
+}
+
+// TestFindLocalCheatpathNotFound tests that empty string is returned when no .cheat exists
+func TestFindLocalCheatpathNotFound(t *testing.T) {
+	tempDir, err := os.MkdirTemp("", "cheat-test-*")
+	if err != nil {
+		t.Fatalf("failed to create temp dir: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	result := findLocalCheatpath(tempDir)
+	if result != "" {
+		t.Errorf("expected empty string, got %s", result)
+	}
+}
+
+// TestFindLocalCheatpathSkipsFile tests that a file named .cheat is not matched
+func TestFindLocalCheatpathSkipsFile(t *testing.T) {
+	tempDir, err := os.MkdirTemp("", "cheat-test-*")
+	if err != nil {
+		t.Fatalf("failed to create temp dir: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	// Create .cheat as a file, not a directory
+	cheatFile := filepath.Join(tempDir, ".cheat")
+	if err := os.WriteFile(cheatFile, []byte("not a directory"), 0644); err != nil {
+		t.Fatalf("failed to create .cheat file: %v", err)
+	}
+
+	result := findLocalCheatpath(tempDir)
+	if result != "" {
+		t.Errorf("expected empty string for .cheat file, got %s", result)
+	}
+}
+
+// TestFindLocalCheatpathSymlink tests that a .cheat symlink to a directory is found
+func TestFindLocalCheatpathSymlink(t *testing.T) {
+	tempDir := t.TempDir()
+
+	// Create the real directory
+	realDir := filepath.Join(tempDir, "real-cheat")
+	if err := os.Mkdir(realDir, 0755); err != nil {
+		t.Fatalf("failed to create real dir: %v", err)
+	}
+
+	// Symlink .cheat -> real-cheat
+	cheatLink := filepath.Join(tempDir, ".cheat")
+	if err := os.Symlink(realDir, cheatLink); err != nil {
+		t.Fatalf("failed to create symlink: %v", err)
+	}
+
+	result := findLocalCheatpath(tempDir)
+	if result != cheatLink {
+		t.Errorf("expected %s, got %s", cheatLink, result)
+	}
+}
+
+// TestFindLocalCheatpathSymlinkInAncestor tests discovery through a symlinked
+// ancestor directory. When the cwd is reached via a symlink, filepath.Dir
+// walks the symlinked path (not the real path), so .cheat must be findable
+// through that chain.
+func TestFindLocalCheatpathSymlinkInAncestor(t *testing.T) {
+	tempDir := t.TempDir()
+
+	// Create real/project/.cheat
+	realProject := filepath.Join(tempDir, "real", "project")
+	if err := os.MkdirAll(realProject, 0755); err != nil {
+		t.Fatalf("failed to create real project dir: %v", err)
+	}
+	if err := os.Mkdir(filepath.Join(realProject, ".cheat"), 0755); err != nil {
+		t.Fatalf("failed to create .cheat dir: %v", err)
+	}
+
+	// Create symlink: linked -> real/project
+	linkedProject := filepath.Join(tempDir, "linked")
+	if err := os.Symlink(realProject, linkedProject); err != nil {
+		t.Fatalf("failed to create symlink: %v", err)
+	}
+
+	// Create sub inside the symlinked path
+	subDir := filepath.Join(linkedProject, "sub")
+	if err := os.Mkdir(subDir, 0755); err != nil {
+		t.Fatalf("failed to create sub dir: %v", err)
+	}
+
+	// Search from linked/sub — should find linked/.cheat
+	// (os.Stat follows symlinks, so linked/.cheat resolves to real/project/.cheat)
+	result := findLocalCheatpath(subDir)
+	expected := filepath.Join(linkedProject, ".cheat")
+	if result != expected {
+		t.Errorf("expected %s, got %s", expected, result)
+	}
+}
+
+// TestFindLocalCheatpathPermissionDenied tests that unreadable ancestor
+// directories are skipped and the walk continues upward.
+func TestFindLocalCheatpathPermissionDenied(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("Unix permissions do not apply on Windows")
+	}
+	if os.Getuid() == 0 {
+		t.Skip("test requires non-root user")
+	}
+
+	tempDir := t.TempDir()
+
+	// Resolve symlinks (macOS /var -> /private/var)
+	tempDir, err := filepath.EvalSymlinks(tempDir)
+	if err != nil {
+		t.Fatalf("failed to resolve symlinks: %v", err)
+	}
+
+	// Create tempDir/.cheat (the target we want found)
+	cheatDir := filepath.Join(tempDir, ".cheat")
+	if err := os.Mkdir(cheatDir, 0755); err != nil {
+		t.Fatalf("failed to create .cheat dir: %v", err)
+	}
+
+	// Create tempDir/restricted/ with its own .cheat and sub/
+	restricted := filepath.Join(tempDir, "restricted")
+	if err := os.Mkdir(restricted, 0755); err != nil {
+		t.Fatalf("failed to create restricted dir: %v", err)
+	}
+	if err := os.Mkdir(filepath.Join(restricted, ".cheat"), 0755); err != nil {
+		t.Fatalf("failed to create restricted .cheat dir: %v", err)
+	}
+	subDir := filepath.Join(restricted, "sub")
+	if err := os.Mkdir(subDir, 0755); err != nil {
+		t.Fatalf("failed to create sub dir: %v", err)
+	}
+
+	// Make restricted/ unreadable — blocks stat of children
+	if err := os.Chmod(restricted, 0000); err != nil {
+		t.Fatalf("failed to chmod: %v", err)
+	}
+	t.Cleanup(func() { os.Chmod(restricted, 0755) })
+
+	// Walk from restricted/sub: stat("restricted/sub/.cheat") fails (EACCES),
+	// stat("restricted/.cheat") fails (EACCES), walk continues to tempDir/.cheat
+	result := findLocalCheatpath(subDir)
+	if result != cheatDir {
+		t.Errorf("expected %s (walked past restricted dir), got %s", cheatDir, result)
+	}
+}
+
 // TestConfig asserts that the configs are loaded correctly
 func TestConfigSuccessful(t *testing.T) {
 
+	// Chdir into a temp directory so no ancestor .cheat directory can
+	// leak into the cheatpaths (findLocalCheatpath walks the full
+	// ancestor chain).
+	oldCwd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("failed to get cwd: %v", err)
+	}
+	defer os.Chdir(oldCwd)
+	if err := os.Chdir(t.TempDir()); err != nil {
+		t.Fatalf("failed to chdir: %v", err)
+	}
+
 	// clear env vars so they don't override the config file value
 	oldVisual := os.Getenv("VISUAL")
 	oldEditor := os.Getenv("EDITOR")