CONTRIBUTING.md - add some notes about feature branches (#659)

- try nudge people towards using a feature branch in their fork instead of their main.
- add note about squash and merge,
- link to an example PR as a sort of reference.
- add a "Tips" section with some tips.

CONTRIBUTING.md

@@ -37,20 +37,28 @@ contributions smoothly we recommend the following:
 1.  Before working on any changes, try to
     [sync the forked repository](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork)
     to keep it up-to-date with the upstream repository.
-1.  Work on a small focused change that only touches on a few files.
+1.  On a
+    [new branch](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/creating-and-deleting-branches-within-your-repository)
+    in your fork (aka a "feature branch" and not `main`) work on a small focused
+    change that only touches on a few files.
 1.  Run `pre-commit` and make sure all files have formatting fixed. This
     simplifies life for reviewers.
 1.  Package up a small bit of work that solves part of the problem
     [into a Pull Request](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/creating-a-pull-request-from-a-fork)
     and
     [send it out for review](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/requesting-a-pull-request-review).
+    [Here](https://github.com/LAION-AI/Open-Assistant/pull/658) is an example PR
+    for this project to illustrate this flow.
 1.  If you're lucky, we can merge your change into `main` without any problems.
     If there's changes to files you're working on, resolve them by:
 1.  First try rebase as suggested
     [in these instructions](https://timwise.co.uk/2019/10/14/merge-vs-rebase/#should-you-rebase).
 1.  If rebase feels too painful, merge as suggested
     [in these instructions](https://timwise.co.uk/2019/10/14/merge-vs-rebase/#should-you-merge).
-1.  Once you've resolved any conflicts, finish the review and merge into `main`.
+1.  Once you've resolved any conflicts, finish the review and
+    [squash and merge](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/incorporating-changes-from-a-pull-request/about-pull-request-merges#squash-and-merge-your-commits)
+    your PR (when squashing try to clean up or update the individual commit
+    messages to be one sensible single one).
 1.  Merge in your change and move onto a new issue or the second step of your
     current issue.
 
@@ -59,6 +67,24 @@ need help on it or would like suggestions on how to approach the issue. If so,
 share wildly. If they seem to have a good handle on it, let them work on their
 solution until a challenge comes up.
 
+#### Tips
+
+- At any point you can compare your feature branch to the upstream/main of
+  `LAION-AI/Open-Assistant` but using a URL like this:
+  https://github.com/LAION-AI/Open-Assistant/compare/main...andrewm4894:Open-Assistant:my-example-feature-branch.
+  Obviously just replace `andrewm4894` with your own GitHub user name and
+  `my-example-feature-branch` with whatever you called the feature branch you
+  are working on, so something like
+  `https://github.com/LAION-AI/Open-Assistant/compare/main...<your_github_username>:Open-Assistant:<your_branch_name>`.
+  This will show the changes that would appear in a PR, so you can check this to
+  make sure it just looks like only the files you have changed or added will be
+  part of the PR.
+- Try not to work on the `main` branch in your fork - ideally you can keep this
+  as just a updated copy of `main` from `LAION-AI/Open-Assistant`.
+- If your feature branch gets messed up, just update the `main` branch in your
+  fork and create a fresh new clean "feature branch" you can try again on by
+  adding your changes one by one in separate commits or all as a single commit.
+
 ### When does a review finish
 
 A review finishes when all blocking comments are addressed and at least one