Editora 0.20.0. Archived, so links from that release keep working. Read the 0.24.0 page →
Diff: Compare with Branch…
diff.vsBranch Diff the current file against a branch you pick.
How to run it
Open the command palette (M-x in the Emacs keymap) and search for Diff: Compare with Branch…, then press Enter. It has no default keybinding, but you can bind one in Settings → Keymaps.