Add dev docs on code formatting

docs/docs/dev/index.md

@@ -1,6 +1,42 @@
-Development
-===========
+# Development
 
 There are opportunities for people of all skills levels to help improve the xemu
 project! Join the xemu community Discord server to chat about ways to apply your
 skills to improve the project.
+
+## Contributing
+
+The xemu project accepts contributions by pull request on the github repository.
+
+Please ensure code is correctly formatted before submitting a pull request.
+This can be done automatically with `git-clang-format`, available with most clang distributions.
+
+```sh
+# Make some changes and stage them
+git add -u
+
+# Format and stage formatter's updates
+git clang-format
+git add -u
+
+# Commit changes with an appropriate message
+git commit -m "subsystem: Description of change"
+```
+
+If the changes have already been committed, the commit hashes can be passed into `git clang-format` as arguments:
+
+```sh
+# Format changes in the last commit
+git clang-format HEAD~1
+
+# Format all commits made on the branch since master
+git clang-format master
+```
+
+After performing either of these commands, the formatting updates must be staged and committed. This can be done
+by amending the commit that was just formatted:
+
+```sh
+git add -u
+git commit --amend
+```