added instructions about commit messages to CONTRIBUTING; bumped version

CONTRIBUTING.md

@@ -100,13 +100,15 @@ For any more significant change that is made (e.g., closing an issue, adding a n
 
 6. Run unit tests and ensure they pass.
 
-7. Create a pull request (PR). **WARNING:** by default, it will want to merge into the `master` branch. Change the destination branch to `dev`.
+7. Commit the changes. In the commit message, reference the issue using the phrase "fixes #123" or "closes #123" (see [here](https://docs.github.com/en/enterprise/2.16/user/github/managing-your-work-on-github/closing-issues-using-keywords)). Also, in the commit message, describe the issue that was fixed (one easy way is to copy the title of the issue); this message will show up in automatically generated release notes, so this is part of the official documentation of what changed.
 
-8. Wait for all checks to complete (see next section), and then merge the changes from the new branch into `dev`. This will typically require someone else to review the code first and possibly request changes.
+8. Create a pull request (PR). **WARNING:** by default, it will want to merge into the `master` branch. Change the destination branch to `dev`.
 
-9. After merging, it will say that the branch you just merged from can be safely deleted. Delete the branch.
+9. Wait for all checks to complete (see next section), and then merge the changes from the new branch into `dev`. This will typically require someone else to review the code first and possibly request changes.
 
-10. Locally, remember to switch back to the `dev` branch and pull it. (Although you added those changes locally, they revert back once you switch to your local `dev` branch, which needs to be synced with the remote repo for you to see the changes that were just merged from the now-deleted temporary branch.)
+10. After merging, it will say that the branch you just merged from can be safely deleted. Delete the branch.
+
+11. Locally, remember to switch back to the `dev` branch and pull it. (Although you added those changes locally, they revert back once you switch to your local `dev` branch, which needs to be synced with the remote repo for you to see the changes that were just merged from the now-deleted temporary branch.)
 
 
 

scadnano/scadnano.py

@@ -44,7 +44,7 @@
 # commented out for now to support Py3.6, which does not support this feature
 # from __future__ import annotations
 
-__version__ = "0.12.1"  # version line; WARNING: do not remove or change this line or comment
+__version__ = "0.12.2"  # version line; WARNING: do not remove or change this line or comment
 
 import dataclasses
 from abc import abstractmethod, ABC