Editora 0.18.3. Archived, so links from that release keep working. Read the 0.18.5 page →
Diff: Compare with Commit…
diff.vsCommit Diff the current file against a commit you pick.
How to run it
Open the command palette (M-x in the Emacs keymap) and search for Diff: Compare with Commit…, then press Enter. It has no default keybinding, but you can bind one in Settings → Keymaps.