Backport #22864
Collapsing folders currently just throws a console error
```
index.js?v=1.19.0~dev-403-gb6b8feb3d:10 TypeError: this.$set is not a function
at Proxy.handleClick (index.js?v=1.19.0~dev-403-gb6b8feb3d:58:7159)
at index.js?v=1.19.0~dev-403-gb6b8feb3d:58:6466
at index.js?v=1.19.0~dev-403-gb6b8feb3d:10:93922
at ce (index.js?v=1.19.0~dev-403-gb6b8feb3d:10:1472)
at Q (index.js?v=1.19.0~dev-403-gb6b8feb3d:10:1567)
at HTMLDivElement.$e (index.js?v=1.19.0~dev-403-gb6b8feb3d:10:79198)
```
This PR fixes this and allows folders to be collapsed again.
Also:
- better cursor interaction with folders
- added some color to the diff detail stats
- remove green link color from all the file names
Screenshots:
![image](https://user-images.githubusercontent.com/9765622/218269712-2f3dda55-6d70-407f-8d34-2a5d9c8df548.png)
![image](https://user-images.githubusercontent.com/9765622/218269714-6ce8a954-daea-4ed6-9eea-8b2323db4d8f.png)
Co-authored-by: gempir <daniel.pasch.s@gmail.com>
Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
This PR adds a filetree to the left side of the files/diff view.
Initially the filetree will not be shown and may be shown via a new
"Show file tree" button.
Showing and hiding is using the same icon as github. Folders are
collapsible. On small devices (max-width 991 PX) the file tree will be
hidden.
Close#18192
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>