path/filepath: fix escaped chars in Glob on non-Windows

Backslashes are ignored in Match and Glob on Windows, since those
collide with the separator character. However, they should still work in
both functions on other operating systems.

hasMeta did not reflect this logic - it always treated a backslash as a
non-special character. Do that only on Windows.

Assuming this is what the TODO was referring to, remove it. There are no
other characters that scanChunk treats especially.

Fixes #23418.

Change-Id: Ie0bd795812e0ed9d8c8c1bbc3137f29d960cba84
Reviewed-on: https://go-review.googlesource.com/87455
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/path/filepath/match.go

@@ -339,6 +339,9 @@ func glob(dir, pattern string, matches []string) (m []string, e error) {
 // hasMeta reports whether path contains any of the magic characters
 // recognized by Match.
 func hasMeta(path string) bool {
-	// TODO(niemeyer): Should other magic characters be added here?
-	return strings.ContainsAny(path, "*?[")
+	magicChars := `*?[`
+	if runtime.GOOS != "windows" {
+		magicChars = `*?[\`
+	}
+	return strings.ContainsAny(path, magicChars)
 }

src/path/filepath/match_test.go

@@ -10,6 +10,7 @@ import (
 	"io/ioutil"
 	"os"
 	. "path/filepath"
+	"reflect"
 	"runtime"
 	"sort"
 	"strings"
@@ -371,3 +372,18 @@ func TestWindowsGlob(t *testing.T) {
 		}
 	}
 }
+
+func TestNonWindowsGlobEscape(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skipf("skipping non-windows specific test")
+	}
+	pattern := `\match.go`
+	want := []string{"match.go"}
+	matches, err := Glob(pattern)
+	if err != nil {
+		t.Fatalf("Glob error for %q: %s", pattern, err)
+	}
+	if !reflect.DeepEqual(matches, want) {
+		t.Fatalf("Glob(%#q) = %v want %v", pattern, matches, want)
+	}
+}