[llvm] [Docs] Add example of making a PR with git and GitHub web interface (PR #65393)

[Michael Maitland via llvm-commits]

================
@@ -207,6 +207,76 @@ See more in-depth information about how to contribute in the following documenta
 * :doc:`Contributing`
 * :doc:`MyFirstTypoFix`
 
+Example Pull Request with git
+====================================
+
+Instead of using the GitHub CLI to create a PR, you can push your code to a
+remote branch on your fork and create the PR to upstream using the GitHub web
+interface.
+
+Here is an example of making a PR using git and the GitHub web interface:
+
+First follow the instructions to [fork the repository](https://docs.github.com/en/get-started/quickstart/fork-a-repo?tool=webui#forking-a-repository).
+
+Next follow the instructions to [clone your forked repository](https://docs.github.com/en/get-started/quickstart/fork-a-repo?tool=webui#cloning-your-forked-repository).
+
+Once you've cloned your forked repository,
+
+::
+
+  # Switch to the forked repo and create a new branch
+  cd llvm-project
+  git switch -c my_change
+
+  # Create your changes
+  $EDITOR file.cpp
+
+  # Don't forget clang-format
+  git clang-format
+
+  # and don't forget running your tests
+  ninja check-llvm
+
+  # Commit, use a good commit message
+  git commit file.cpp
+
+  # Push your changes to your fork branch, be mindful of
+  # your remotes here, if you don't remember what points to your
+  # fork, use git remote -v to see. Usually origin points to your
+  # fork and upstream to llvm/llvm-project
+  git push origin my_change
+
+Now back on the GitHub web interface, navigate to your fork and create a pull
+request from your branch to llvm::main.
+
+::
+
+  # If you get any review comments, come back to the branch and
+  # adjust them.
+  git switch my_change
+  $EDITOR file.cpp
+
+  # Commit your changes
+  git commit file.cpp -m "Code Review adjustments"
+
+  # Push your changes to your fork branch, be mindful of
+  # your remotes here, if you don't remember what points to your
+  # fork, use git remote -v to see. Usually origin points to your
+  # fork and upstream to llvm/llvm-project
+  git push origin my_change
+
+  # When your PR is accepted, you can now rebase it and make sure
+  # you have all the latest changes.
+  git rebase -i origin/main
----------------
michaelmaitland wrote:

From the docs above: `After your PR is reviewed and accepted, you want to rebase your branch to ensure you won’t encounter merge conflicts when landing the PR.`

Maybe what we'd like is to move the rebase and ninja steps to be placed above pushing changes to the branch. WDYT?

https://github.com/llvm/llvm-project/pull/65393