fix: mark copy-only diff target as Added in DiffView

- parse copy metadata so copy target gets Added state (A icon)
- update state tracking to apply to displayed target path only
- avoid listing copy source as a separate file entry
- add/strengthen tests for copy-only and incremental copy metadata parsing

Author: timxx

qgitc/difffetcher.py

@@ -39,21 +39,20 @@ def parse(self, data: bytes):
         lines = data.split(self.separator)
         fullFileAStr = None
         fullFileBStr = None
+        fullDisplayFileStr = None
         fileState = FileState.Normal
 
         def _updateFileState():
-            nonlocal fullFileAStr, fullFileBStr, fileState
+            nonlocal fullFileAStr, fullFileBStr, fullDisplayFileStr, fileState
             if fileState != FileState.Normal:
-                if fullFileAStr:
-                    self._fileStates[fullFileAStr] = fileState
-                    if fullFileAStr in fileItems:
-                        fileItems[fullFileAStr].state = fileState
-                if fullFileBStr:
-                    self._fileStates[fullFileBStr] = fileState
-                    if fullFileBStr in fileItems:
-                        fileItems[fullFileBStr].state = fileState
+                fileToUpdate = fullDisplayFileStr or fullFileBStr or fullFileAStr
+                if fileToUpdate:
+                    self._fileStates[fileToUpdate] = fileState
+                    if fileToUpdate in fileItems:
+                        fileItems[fileToUpdate].state = fileState
             fullFileAStr = None
             fullFileBStr = None
+            fullDisplayFileStr = None
             fileState = FileState.Normal
 
         for line in lines:
@@ -75,13 +74,6 @@ def _updateFileState():
 
                 fullFileA = self.makeFilePath(fileA)
                 fullFileAStr = fullFileA.decode(diff_encoding)
-                fileItems[fullFileAStr] = FileInfo(self._row)
-                # Apply previously tracked state from earlier parse calls
-                if fullFileAStr in self._fileStates:
-                    fileItems[fullFileAStr].state = self._fileStates[fullFileAStr]
-
-                # Store current file for incremental parsing
-                self._currentFileA = fullFileAStr
 
                 # renames, keep new file name only
                 if fileB and fileB != fileA:
@@ -91,9 +83,17 @@ def _updateFileState():
                     fileItems[fullFileBStr] = FileInfo(self._row)
                     if fullFileBStr in self._fileStates:
                         fileItems[fullFileBStr].state = self._fileStates[fullFileBStr]
+                    fullDisplayFileStr = fullFileBStr
+                    self._currentFileA = fullFileAStr
                     self._currentFileB = fullFileBStr
                 else:
                     lineItems.append((DiffType.File, fullFileA))
+                    fileItems[fullFileAStr] = FileInfo(self._row)
+                    # Apply previously tracked state from earlier parse calls
+                    if fullFileAStr in self._fileStates:
+                        fileItems[fullFileAStr].state = self._fileStates[fullFileAStr]
+                    fullDisplayFileStr = fullFileAStr
+                    self._currentFileA = fullFileAStr
                     self._currentFileB = None
 
                 self._row += 1
@@ -146,35 +146,27 @@ def _updateFileState():
                         fileState = FileState.Renamed
                     elif fileState == FileState.Modified:
                         fileState = FileState.RenamedModified
+                elif line.startswith(b"copy to "):
+                    fileState = FileState.Added
                 elif line.startswith(b"index "):
                     if fileState == FileState.Renamed:
                         fileState = FileState.RenamedModified
                     elif fileState == FileState.Normal:
                         fileState = FileState.Modified
 
-                fileAToUpdate = fullFileAStr or self._currentFileA
-                fileBToUpdate = fullFileBStr or self._currentFileB
-
-                if fileAToUpdate:
-                    oldState = self._fileStates.get(fileAToUpdate)
-                    self._fileStates[fileAToUpdate] = fileState
-                    # If file not in fileItems yet (metadata from previous chunk)
-                    if fileAToUpdate not in fileItems:
-                        if oldState != fileState:
-                            self.fileStateChanged.emit(
-                                fileAToUpdate, fileState)
-                    else:
-                        fileItems[fileAToUpdate].state = fileState
-
-                if fileBToUpdate:
-                    oldState = self._fileStates.get(fileBToUpdate)
-                    self._fileStates[fileBToUpdate] = fileState
-                    if fileBToUpdate not in fileItems:
-                        if oldState != fileState:
-                            self.fileStateChanged.emit(
-                                fileBToUpdate, fileState)
-                    else:
-                        fileItems[fileBToUpdate].state = fileState
+                if fileState != FileState.Normal:
+                    fileToUpdate = fullDisplayFileStr or fullFileBStr or \
+                        fullFileAStr or self._currentFileB or self._currentFileA
+                    if fileToUpdate:
+                        oldState = self._fileStates.get(fileToUpdate)
+                        self._fileStates[fileToUpdate] = fileState
+                        # If file not in fileItems yet (metadata from previous chunk)
+                        if fileToUpdate not in fileItems:
+                            if oldState != fileState:
+                                self.fileStateChanged.emit(
+                                    fileToUpdate, fileState)
+                        else:
+                            fileItems[fileToUpdate].state = fileState
 
             if itemType != DiffType.Diff:
                 line = line.rstrip(b'\r')

tests/test_difffetcher.py

@@ -736,9 +736,12 @@ def test_copy_file(self):
             b'\x00'
         ])
 
-        lineItems, fileItems = self._parse_and_get_results(diff_data)
+        _, fileItems = self._parse_and_get_results(diff_data)
 
+        self.assertNotIn('original.txt', fileItems)
         self.assertIn('copy.txt', fileItems)
+        self.assertEqual(fileItems['copy.txt'].state, FileState.Added,
+                 "Copy target should be Added")
 
     def test_no_newline_at_end_of_file(self):
         """

tests/test_difffetcher_bugs.py

@@ -485,3 +485,36 @@ def test_true_incremental_parsing_across_calls(self):
         # foo.txt should NOT be in fileItems2 since it's a state-only update
         self.assertNotIn('foo.txt', fileItems2,
                          "foo.txt should not be in fileItems2 (emitted via fileStateChanged instead)")
+
+    def test_true_incremental_copy_metadata_updates_target_state(self):
+        """copy metadata in a later chunk should emit Added for copy target."""
+        chunk1 = b'\x00'.join([
+            b'diff --git a/guides/README.md b/.github/copilot-instructions.md',
+            b'\x00'
+        ])
+
+        _, fileItems1 = self._parse(chunk1)
+        self.assertIn('.github/copilot-instructions.md', fileItems1)
+        self.assertEqual(
+            fileItems1['.github/copilot-instructions.md'].state,
+            FileState.Normal
+        )
+
+        self.stateChanges.clear()
+
+        chunk2 = b'\x00'.join([
+            b'similarity index 100%',
+            b'copy from guides/README.md',
+            b'copy to .github/copilot-instructions.md',
+            b'\x00'
+        ])
+
+        _, fileItems2 = self._parse(chunk2, reset=False)
+
+        self.assertNotIn('.github/copilot-instructions.md', fileItems2)
+        self.assertEqual(len(self.stateChanges), 1)
+        self.assertEqual(
+            self.stateChanges[0][0],
+            '.github/copilot-instructions.md'
+        )
+        self.assertEqual(self.stateChanges[0][1], FileState.Added)