use the proper caret offset in case of selection. Do not overindent when replacing selection

PY-8744 Smart indent pasted lines doesn't replace selection when pasting multi-line code

python/src/com/jetbrains/python/editor/PythonCopyPasteProcessor.java

@@ -58,7 +58,7 @@ public class PythonCopyPasteProcessor implements CopyPastePreProcessor {
           final int line = document.getLineNumber(selectionModel.getSelectionStart());
           final int lineOffset = getLineStartSafeOffset(document, line);
           final PsiElement ws = file.findElementAt(lineOffset);
-          int offset = ws instanceof PsiWhiteSpace? ws.getTextRange().getEndOffset() : caretOffset;
+          int offset = ws instanceof PsiWhiteSpace? ws.getTextRange().getEndOffset() : selectionModel.getSelectionStart();
           if (text.equals(selectionModel.getSelectedText())) return text;
           caretModel.moveToOffset(offset);
           selectionModel.setSelection(offset, selectionModel.getSelectionEnd());

python/testData/copyPaste/ReplaceSelection.after.py

@@ -0,0 +1,4 @@
+a = 1
+b = 1
+a = 1
+b = 1

python/testData/copyPaste/ReplaceSelection.dst.py

@@ -0,0 +1,4 @@
+a = 1
+b = 1
+<selection>c = 1
+</selection><caret>

python/testData/copyPaste/ReplaceSelection.src.py

@@ -0,0 +1,3 @@
+<selection>a = 1
+b = 1
+</selection><caret>c = 1

python/testSrc/com/jetbrains/python/PyCopyPasteTest.java

@@ -263,6 +263,10 @@ public class PyCopyPasteTest extends PyTestCase {
     doTest();
   }
 
+  public void testReplaceSelection() {    //PY-8744
+    doTest();
+  }
+
   private void doTest() {
     String name = getTestName(false);