update-existing-pkg: Add suitable shortlog examples

The reasoning is the same as for the new packages.

The git shortlog examples shown in this in this commit have already
been proven useful in the context of the serpent recipe monorepo.

Signed-off-by: Rune Morling <ermo@serpentos.com>

docs/packaging/updating-an-existing-package.md

@@ -167,6 +167,20 @@ Full release notes:
 - [ ] Package was built and tested against unstable
 ```
 
+### Other commit message format examples
+
+In the cases where you are not updating a package to a new version, but simply applying a patch of fixing an existing version, the following commit message shortlogs are considered suitable:
+
+- Add the `homepage` metatdata key:
+  `package: Add homepage`
+- Fix a packaging issue (including adding a patch to fix the package)
+  `package: Fix (...)`
+- Updating a README, monitoring.yml file or other stuff that does not directly _change_ the package, meaning the package release number didn't need a bump:
+  `package: [NFC] Add README.md and monitoring.yml`
+`[NFC]` is an abbreviation adopted from the clang compiler suite, which expands to "Non Functional Change".
+
+The overall reasoning for the git shortlog formats shown above is to enable quick and efficient "at-a-glance" parsing of git shortlogs for Solus Staff.
+
 For more information on suitable commit messages, please check the [tooling central documentation](https://github.com/solus-project/tooling-central/blob/master/README.rst#using-git).
 
 Next, you'll [submit a pull request for review](submitting-a-pull-request.md).