Fix Incorrect File Selection in Merge Conflict Window Directory Tree by Preserving Expanded State

[Khukhunashvili]

Problem:

When users collapse directories in the Merge Conflict window pop up and a refresh occurs (triggered by updateModelFromFiles(), for example when I open the file for merge and close it immediately), the previously selected file could be reselected incorrectly.

This issue stems from table.selectionModel.minSelectionIndex not accounting for the visibility (expanded/collapsed state) of files in the directory tree. Consequently, when the updateTree() function expands all directories during a refresh, the indices of files change, leading to a mismatch between the intended and actual selections.

Here is the visualization of the problem: https://imgur.com/gallery/sjJe84Y

Solution:

To address this issue, I implemented a strategy to preserve the user's context in the directory tree across updates. The solution involves the following steps:

1. Save Expanded Paths
2. After updateTree() function is invoked, collapse the entire tree.
3. Restore expanded paths

This approach ensures that the directory tree's structure post-update remains identical to its state prior to the update. Consequently, the index saved in selIndex remains consistent.