filepath.Clean() the include paths (#124)

This normalizes the include path strings for use throughout the linter,
parser, and checks.

See: https://pkg.go.dev/path/filepath#Clean

Author: jparise

README.md

@@ -44,6 +44,11 @@ Use `--stdin-name` to customize the filename used in output messages.
 $ thriftlint --stdin-name filename.thrift - < filename.thrift
 ```
 
+Include paths specified via `-I` or in the configuration file are normalized
+using lexical path cleaning, which removes trailing slashes, resolves `.` and
+`..` elements, and eliminates redundant separators. This means `includes/`,
+`includes`, and `./includes/` are treated identically.
+
 Messages are reported to standard output using a familiar parseable format:
 
 ```

linter.go

@@ -48,7 +48,9 @@ func WithLogger(logger *log.Logger) Option {
 // WithIncludes is an Option that adds Thrift include paths to the linter.
 func WithIncludes(includes []string) Option {
 	return func(l *Linter) {
-		l.includes = includes
+		for _, dir := range includes {
+			l.includes = append(l.includes, filepath.Clean(dir))
+		}
 	}
 }
 

linter_test.go

@@ -33,10 +33,11 @@ func TestWithLogger(t *testing.T) {
 }
 
 func TestWithIncludes(t *testing.T) {
-	includes := []string{"a", "b"}
+	includes := []string{"a", "b/", "../c/..", "/d", "./e", ""}
+	expected := []string{"a", "b", "..", "/d", "e", "."}
 	linter := NewLinter(Checks{}, WithIncludes(includes))
-	if !reflect.DeepEqual(linter.includes, includes) {
-		t.Errorf("expected includes to be %v, got %v", includes, linter.includes)
+	if !reflect.DeepEqual(linter.includes, expected) {
+		t.Errorf("expected includes to be %v, got %v", expected, linter.includes)
 	}
 }