Right now I'm using meld, but it shows differences only for one file, and if you have few changed files you have to close meld window, then it suggests to open a new window with differences for next file, and so on. Is there any GUI tool that can show differences for all files in one window, somewhat familiar to how it's done in GitHub, for example when you are looking through Pull Request changes, with split mode and stuff?
If you call :
git difftool -d
to invoke your graphical diff viewer, it will open in a "directory diff" mode.
meld for example presents you with an overview of all different files, and you can view the differences for each individual file by double clicking.