ci: release revisions of an upstream version

README.md

@@ -163,6 +163,10 @@ scripts/prepare.sh
   published a newer release than `upstream.txt`, it rebuilds against it and — only if every
   platform built and every check passed — commits the bump, tags it with the upstream version and
   publishes a release with the installers.
+- **Revisions** of the same upstream release are published by running Upstream release by hand
+  with `revision` ticked. It builds the upstream release in `upstream.txt` again with the current
+  patches and publishes it as `v0.21.2-2`, `v0.21.2-3` and so on. The app and installers still
+  carry the upstream version: RPM and the Windows installers do not accept a suffix in it.
 
 `scripts/check.sh` is what makes the automation trustworthy. A patch can apply cleanly and still
 stop doing its job if upstream moves the thing it was holding down, so the checks assert the