update release guide

doc/README.md

@@ -6,15 +6,20 @@ The iminuit logo uses glyphs generated from the free Gentium Plus font.
 How to make a release
 =====================
 
+- On develop
+  - Update `src/iminuit/version.py` to released version
+  - Update `doc/changelog.rst` to released version and add today's date
+  - Note: A prerelease can be published simply by adding `.rcN` to `iminuit_version`,
+    where N is a number >= 0
 - Merge develop into master
   - Option: do a `git rebase -i` to make history edits
-- Create a branch on the master, called release_<version>, make release edits there
-  - Increase version number in iminuit/version.py
-  - Update doc/changelog.rst
-  - Check that all wheels are build (Azure should trigger)
-- Merge release branch to master
+- Check that all wheels are build and run fine
+  - If there are problems with the wheels, create a beta/<release-version> branch and
+    commit fixes there, once the problem is fixed, squash-merge the branch to master
 - Create release on Github
-  - This triggers an upload of the latest build artefacts to PyPI
-  - Note: a prerelease is published on TestPyPI, a release on PyPI
-  - Upload uses API tokens configured in PyPI, TestPyPI, and Github "Secrets"
-- Conda-forge should pick this up automatically and generate conda packages
+  - Message: [See changelog on RTD](https://iminuit.readthedocs.io/en/stable/changelog.html)
+- This triggers an upload of the latest build artefacts to PyPI
+  - If this fails unexpectedly, download the artefact from the actions page and upload
+    it manually with twine, then fix the issue for the next release
+  - Upload uses API tokens configured in PyPI and Github "Secrets"
+- conda-forge should pick this up automatically and generate conda packages