lib/db: Don't whack blocks when putting truncated file (#6434)

As of the latest database checker we are again putting files without
blocks. I'm not 100% convinced that's a great idea, but we also do it
for ignored files apparently so it looks like we probably should support
it. This adds an escape hatch that must be manually enabled...

lib/db/db_test.go

@@ -261,11 +261,11 @@ func TestRepairSequence(t *testing.T) {
 	short := protocol.LocalDeviceID.Short()
 
 	files := []protocol.FileInfo{
-		{Name: "fine"},
-		{Name: "duplicate"},
-		{Name: "missing"},
-		{Name: "overwriting"},
-		{Name: "inconsistent"},
+		{Name: "fine", Blocks: genBlocks(1)},
+		{Name: "duplicate", Blocks: genBlocks(2)},
+		{Name: "missing", Blocks: genBlocks(3)},
+		{Name: "overwriting", Blocks: genBlocks(4)},
+		{Name: "inconsistent", Blocks: genBlocks(5)},
 	}
 	for i, f := range files {
 		files[i].Version = f.Version.Update(short)
@@ -282,7 +282,7 @@ func TestRepairSequence(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
-		if err := trans.putFile(dk, f); err != nil {
+		if err := trans.putFile(dk, f, false); err != nil {
 			t.Fatal(err)
 		}
 		sk, err := trans.keyer.GenerateSequenceKey(nil, folder, seq)
@@ -399,16 +399,20 @@ func TestRepairSequence(t *testing.T) {
 	}
 	defer it.Release()
 	for it.Next() {
-		fi, ok, err := ro.getFileTrunc(it.Value(), true)
+		intf, ok, err := ro.getFileTrunc(it.Value(), false)
 		if err != nil {
 			t.Fatal(err)
 		}
+		fi := intf.(protocol.FileInfo)
 		seq := ro.keyer.SequenceFromSequenceKey(it.Key())
 		if !ok {
 			t.Errorf("Sequence entry %v points at nothing", seq)
 		} else if fi.SequenceNo() != seq {
 			t.Errorf("Inconsistent sequence entry for %v: %v != %v", fi.FileName(), fi.SequenceNo(), seq)
 		}
+		if len(fi.Blocks) == 0 {
+			t.Error("Missing blocks in", fi.FileName())
+		}
 	}
 	if err := it.Error(); err != nil {
 		t.Fatal(err)