os symlink use rel path

os.go

@@ -16,6 +16,7 @@ package afero
 
 import (
 	"os"
+	"path/filepath"
 	"time"
 )
 
@@ -105,7 +106,11 @@ func (OsFs) LstatIfPossible(name string) (os.FileInfo, bool, error) {
 }
 
 func (OsFs) SymlinkIfPossible(oldname, newname string) error {
-	return os.Symlink(oldname, newname)
+	relpath, err := filepath.Rel(filepath.Dir(newname), oldname)
+	if err != nil {
+		return &os.LinkError{Op: "symlink", Old: oldname, New: newname, Err: err}
+	}
+	return os.Symlink(relpath, newname)
 }
 
 func (OsFs) ReadlinkIfPossible(name string) (string, error) {

symlink_test.go

@@ -132,14 +132,15 @@ func TestReadlinkIfPossible(t *testing.T) {
 	}
 
 	testRead := func(r LinkReader, name string, output *string) {
-		_, err := r.ReadlinkIfPossible(name)
+		str, err := r.ReadlinkIfPossible(name)
 		if (err != nil) && (output == nil) {
 			t.Fatalf("Error reading link, expected success, got error: %v", err)
 		} else if (err == nil) && (output != nil) {
 			t.Fatalf("Error reading link, succeeded when expecting error: %v", *output)
 		} else if err != nil && err.Error() != *output && !strings.HasSuffix(err.Error(), *output) {
 			t.Fatalf("Error reading link, expected error '%v', instead received '%v'", *output, err)
 		}
+		t.Logf("str: %v", str)
 	}
 
 	notSupported := ErrNoReadlink.Error()