lib/scanner, lib/fs: Don't create file infos with abs paths (fixes #4799) (#4800)

lib/scanner/walk_test.go

@@ -498,6 +498,30 @@ func TestStopWalk(t *testing.T) {
 	}
 }
 
+func TestIssue4799(t *testing.T) {
+	tmp, err := ioutil.TempDir("", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmp)
+
+	fs := fs.NewFilesystem(fs.FilesystemTypeBasic, tmp)
+
+	fd, err := fs.Create("foo")
+	if err != nil {
+		t.Fatal(err)
+	}
+	fd.Close()
+
+	files, err := walkDir(fs, "/foo")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(files) != 1 || files[0].Name != "foo" {
+		t.Error(`Received unexpected file infos when walking "/foo"`, files)
+	}
+}
+
 // Verify returns nil or an error describing the mismatch between the block
 // list and actual reader contents
 func verify(r io.Reader, blocksize int, blocks []protocol.BlockInfo) error {