fix, new diff dialog action didn't work due to with statement

also the position in view was reset, which was not something
  we want

CHANGELOG.md

@@ -1,3 +1,9 @@
+# v3.9.2-dev
+
+## Bugs fixed
+
+- Editor, Diff: the button used to "reload from disk and reset the history" didn't work.
+
 # v3.9.1
 
 ## Bugs fixed

src/u_synmemo.pas

@@ -3449,6 +3449,7 @@ var
   curMd5  : TMDDigest;
   str     : TStringList;
   newTxt  : string;
+  p       : TPoint;
 begin
   if fDiffDialogWillClose or fDisableFileDateCheck then
     exit;
@@ -3488,9 +3489,11 @@ begin
           end;
           mrAll:
           begin
+            p         := self.CaretXY;
             fModified := false;
-            text      := newTxt;
+            self.text := newTxt;
             fFileDate := newDate;
+            CaretXY   := p;
           end;
           mrIgnore:
           begin