Fix Git path normalization

Author: BakerNet

internal/git/file_reader.go

@@ -23,8 +23,8 @@ func NewGitRefFileReader(ref string, dir string) *GitRefFileReader {
 
 // ReadFile reads a file from the git ref
 func (r *GitRefFileReader) ReadFile(path string) ([]byte, error) {
-	// Normalize path - remove leading slash if present
-	path = strings.TrimPrefix(path, "/")
+	// Normalize path - make it relative to the repository root
+	path = r.normalizePathForGit(path)
 
 	// Use git show to read the file from the ref
 	output, err := r.executor.execute("git", "show", fmt.Sprintf("%s:%s", r.ref, path))
@@ -36,10 +36,24 @@ func (r *GitRefFileReader) ReadFile(path string) ([]byte, error) {
 
 // PathExists checks if a file exists in the git ref
 func (r *GitRefFileReader) PathExists(path string) bool {
-	// Normalize path - remove leading slash if present
-	path = strings.TrimPrefix(path, "/")
+	// Normalize path - make it relative to the repository root
+	path = r.normalizePathForGit(path)
 
 	// Use git cat-file to check if the file exists
 	_, err := r.executor.execute("git", "cat-file", "-e", fmt.Sprintf("%s:%s", r.ref, path))
 	return err == nil
 }
+
+// normalizePathForGit converts an absolute filesystem path to a path relative to the repository root
+func (r *GitRefFileReader) normalizePathForGit(path string) string {
+	// We want to remove the path to the dir Root
+	dir_prefix := r.dir
+	if !strings.HasSuffix(dir_prefix, "/") {
+		dir_prefix = dir_prefix + "/"
+	}
+	path = strings.TrimPrefix(path, dir_prefix)
+	if strings.HasPrefix(path, "/") {
+		return path[1:]
+	}
+	return path
+}

internal/git/file_reader_path_normalization_test.go

@@ -0,0 +1,80 @@
+package git
+
+import (
+	"testing"
+)
+
+// TestGitRefFileReader_PathNormalization tests that absolute paths are correctly
+// normalized to be relative to the repository root
+func TestGitRefFileReader_PathNormalization(t *testing.T) {
+	tt := []struct {
+		name     string
+		repoDir  string
+		input    string
+		expected string
+	}{
+		{
+			name:     "relative path unchanged",
+			repoDir:  "/repo",
+			input:    ".codeowners",
+			expected: ".codeowners",
+		},
+		{
+			name:     "absolute path stripped",
+			repoDir:  "/repo",
+			input:    "/repo/.codeowners",
+			expected: ".codeowners",
+		},
+		{
+			name:     "nested path with repo prefix",
+			repoDir:  "/repo",
+			input:    "/repo/internal/app/.codeowners",
+			expected: "internal/app/.codeowners",
+		},
+		{
+			name:     "current directory repo with relative path",
+			repoDir:  ".",
+			input:    "./.codeowners",
+			expected: ".codeowners",
+		},
+		{
+			name:     "github workspace path",
+			repoDir:  "/github/workspace",
+			input:    "/github/workspace/.codeowners",
+			expected: ".codeowners",
+		},
+		{
+			name:     "github workspace nested path",
+			repoDir:  "/github/workspace",
+			input:    "/github/workspace/internal/app/.codeowners",
+			expected: "internal/app/.codeowners",
+		},
+		{
+			name:     "path not under repo dir",
+			repoDir:  "/repo",
+			input:    "/other/.codeowners",
+			expected: "other/.codeowners",
+		},
+		{
+			name:     "repo dir without trailing slash",
+			repoDir:  "/repo/",
+			input:    "/repo/subdir/.codeowners",
+			expected: "subdir/.codeowners",
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			reader := &GitRefFileReader{
+				ref: "test-ref",
+				dir: tc.repoDir,
+			}
+
+			result := reader.normalizePathForGit(tc.input)
+			if result != tc.expected {
+				t.Errorf("normalizePathForGit(%q) with dir=%q = %q, want %q",
+					tc.input, tc.repoDir, result, tc.expected)
+			}
+		})
+	}
+}

internal/git/file_reader_test.go

@@ -68,6 +68,18 @@ func TestGitRefFileReader_ReadFile(t *testing.T) {
 			expected:    "* @owner1\n",
 			expectError: false,
 		},
+		{
+			name:        "read with absolute path including repo dir",
+			path:        "/repo/.codeowners",
+			expected:    "* @owner1\n",
+			expectError: false,
+		},
+		{
+			name:        "read subdirectory with absolute path",
+			path:        "/repo/subdir/.codeowners",
+			expected:    "*.js @owner2\n",
+			expectError: false,
+		},
 	}
 
 	for _, tc := range tt {
@@ -129,6 +141,11 @@ func TestGitRefFileReader_PathExists(t *testing.T) {
 			path:     "/.codeowners",
 			expected: true,
 		},
+		{
+			name:     "existing file with absolute path",
+			path:     "/repo/.codeowners",
+			expected: true,
+		},
 	}
 
 	for _, tc := range tt {