Add a PR review section to CONTRIBUTING.md

CONTRIBUTING.md

@@ -16,6 +16,7 @@ bug reports and features requests or writing code to add enhancements or fix bug
 7. [Source Code Patches](#contributing-patches-source-code)
 8. [Documentation Patches](#contributing-patches-documentation)
 9. [Contribute CheckCommand Definitions](#contributing-patches-itl-checkcommands)
+10. [Review](#contributing-review)
 
 ## <a id="contributing-intro"></a> Introduction
 
@@ -439,3 +440,58 @@ hub pull-request
 In case developers ask for changes during review, please add them
 to the branch and push those changes.
 
+## <a id="contributing-review"></a> Review
+
+### <a id="contributing-pr-review"></a> Pull Request Review
+
+This is only important for developers who will review pull requests. If you want to join
+the development team, kindly contact us.
+
+- Ensure that the style guide applies.
+- Verify that the patch fixes a problem or linked issue, if any.
+- Discuss new features with team members.
+- Test the patch in your local dev environment.
+
+If there are changes required, kindly ask for an updated patch.
+
+Once the review is completed, merge the PR via GitHub.
+
+#### <a id="contributing-pr-review-fixes"></a> Pull Request Review Fixes
+
+In order to amend the commit message, fix conflicts or add missing changes, you can
+add your changes to the PR.
+
+A PR is just a pointer to a different Git repository and branch.
+By default, pull requests allow to push into the repository of the PR creator.
+
+Example for [#4956](https://github.com/Icinga/icinga2/pull/4956):
+
+At the bottom it says "Add more commits by pushing to the fix/persistent-comments-are-not-persistent branch on TheFlyingCorpse/icinga2."
+
+First off, add the remote repository as additional origin and fetch its content:
+
+```
+git remote add theflyingcorpse https://github.com/TheFlyingCorpse/icinga2
+git fetch --all
+```
+
+Checkout the mentioned remote branch into a local branch (Note: `theflyingcorpse` is the name of the remote):
+
+```
+git checkout theflyingcorpse/fix/persistent-comments-are-not-persistent -b fix/persistent-comments-are-not-persistent
+```
+
+Rebase, amend, squash or add your own commits on top.
+
+Once you are satisfied, push the changes to the remote `theflyingcorpse` and its branch `fix/persistent-comments-are-not-persistent`.
+The syntax here is `git push <remote> <localbranch>:<remotebranch>`.
+
+```
+git push theflyingcorpse fix/persistent-comments-are-not-persistent:fix/persistent-comments-are-not-persistent
+```
+
+In case you've changed the commit history (rebase, amend, squash), you'll need to force push. Be careful, this can't be reverted!
+
+```
+git push -f theflyingcorpse fix/persistent-comments-are-not-persistent:fix/persistent-comments-are-not-persistent
+```