restore: Fix small memory leak in filesWriter, add tests

Signed-off-by: Igor Fedorenko <igor@ifedorenko.com>

internal/restorer/fileswriter.go

@@ -66,4 +66,5 @@ func (w *filesWriter) close(file *fileInfo) {
 	w.lock.Lock()
 	defer w.lock.Unlock()
 	w.writers.Remove(file)
+	delete(w.inprogress, file)
 }

internal/restorer/fileswriter_test.go

@@ -0,0 +1,44 @@
+package restorer
+
+import (
+	"io/ioutil"
+	"testing"
+
+	rtest "github.com/restic/restic/internal/test"
+)
+
+func TestFilesWriterBasic(t *testing.T) {
+	dir, cleanup := rtest.TempDir(t)
+	defer cleanup()
+
+	w := newFilesWriter(1)
+
+	f1 := &fileInfo{path: dir + "/f1"}
+	f2 := &fileInfo{path: dir + "/f2"}
+
+	rtest.OK(t, w.writeToFile(f1, []byte{1}))
+	rtest.Equals(t, 1, w.writers.Len())
+	rtest.Equals(t, 1, len(w.inprogress))
+
+	rtest.OK(t, w.writeToFile(f2, []byte{2}))
+	rtest.Equals(t, 1, w.writers.Len())
+	rtest.Equals(t, 2, len(w.inprogress))
+
+	rtest.OK(t, w.writeToFile(f1, []byte{1}))
+	w.close(f1)
+	rtest.Equals(t, 0, w.writers.Len())
+	rtest.Equals(t, 1, len(w.inprogress))
+
+	rtest.OK(t, w.writeToFile(f2, []byte{2}))
+	w.close(f2)
+	rtest.Equals(t, 0, w.writers.Len())
+	rtest.Equals(t, 0, len(w.inprogress))
+
+	buf, err := ioutil.ReadFile(f1.path)
+	rtest.OK(t, err)
+	rtest.Equals(t, []byte{1, 1}, buf)
+
+	buf, err = ioutil.ReadFile(f2.path)
+	rtest.OK(t, err)
+	rtest.Equals(t, []byte{2, 2}, buf)
+}