Document the release process (#1611)

holidays/RELEASE.rst

@@ -0,0 +1,69 @@
+How to release a new version of Python Holidays
+===============================================
+
+- Finalize the current development version
+
+  - switch to ``beta`` branch and pull the most recent changes
+    from https://github.com/vacanza/python-holidays remote ``beta`` branch.
+  - generate release notes by running the following script
+    ``scripts/generate_release_notes.py -t <version>``, where <version> is the
+    value of tag/version you're going to release, e.g. 0.39
+  - insert the script's output into the top of ``CHANGES`` file
+    (see previous release notes for consistent formatting)
+  - commit the updated ``CHANGES`` file to ``beta`` branch with the following
+    commit message 'Finalize v<version>', e.g. 'Finalize v0.39'
+  - push changes to https://github.com/vacanza/python-holidays ``beta`` branch
+  - make sure the push related CI/CD job(s) have been completed successfully
+
+- Merge the finalized changes into ``master`` branch:
+
+  - create a new PR for the recent changes from ``beta`` to ``master`` branch
+    using 'v<version>' as a PR title and the previously generated release notes
+    as a PR description
+  - get the PR reviewed by at least one of the code owners
+  - merge the PR into ``master`` branch with 'Create a merge commit' action
+    (**do not use 'Squash and merge'**)
+  - make sure the PR related CI/CD job(s) have been completed successfully
+  - make sure readthedocs.org documentation build jobs at
+    https://readthedocs.org/projects/python-holidays/builds/
+    have been completed successfully
+
+- Create a new release:
+
+  - open https://github.com/vacanza/python-holidays/releases page and click
+    on the 'Draft a new release' button
+  - click on 'Choose a tag', enter 'v<version>' into the input field
+    (you should see something like 'Create a new tag: v0.39' on publish'
+  - select **master** - instead of default ``beta`` in 'Target' dropdown
+  - put 'v<version>' into 'Release title' field, e.g. 'v0.39'
+  - click on 'Generate release notes' button to collect new contributors and
+    full changelog link information (we normally keep it at the bottom with
+    a bit of re-formatting)
+  - replace auto-generated release notes with the previously generated release
+    notes (keep the new contributors and full changelog link)
+  - check/uncheck the 'Set as the latest release' checkbox depending on the
+    release status
+  - save the draft (do not publish it yet)
+  - preview the release on https://github.com/vacanza/python-holidays/releases
+  - after making sure everything looks right click 'Edit' and then
+    'Publish release'
+
+- Verify the new release:
+
+  - make sure the release related CI/CD job(s) have been completed successfully
+  - check https://pypi.org/project/holidays/ package page -- it should have
+    the current version and the released date updated
+
+- Finish the process with the following post-release actions:
+
+  - send "Python Holidays 'v<version>' has been released!" (or similar) message
+    to Vacanza Team Slack #release channel
+  - pull the recent changes from ``master`` branch into ``beta``
+  - bump the Python Holidays version at ``holidays/__init__.py`` file
+  - create a commit with 'Initialize v<version>' message, e.g.
+    'Initialize v0.40' and push it to ``beta`` branch (this may require
+    running ``make package`` to pass the tests locally)
+  - make sure ``beta`` branch **is not behind** the master branch (there
+    will be a message on top of the
+    https://github.com/vacanza/python-holidays/tree/beta page in case it is)
+  - make sure the push related CI/CD job(s) have been completed successfully