Undo Multiple Commits

Adds an Undo Multiple Commits... entry to the Source Control view, right after Undo Last Commit in the ... > Commit submenu.

Asks how many commits to undo, shows the commits that will be undone (with warnings for merge commits and already-pushed commits), then runs git reset --soft HEAD~N. File changes are kept staged, and the undone commit messages are restored into the commit message box.

Also available from the Command Palette: Git: Undo Multiple Commits...