docs: Clarify squash in CONTRIBUTING

Closes: #2736
Signed-off-by: Michael Gasch <[email protected]>

Author: Michael Gasch

CONTRIBUTING.md

@@ -109,30 +109,34 @@ $ git push --force-with-lease $USER issue-<number>
 
 ### Updating Pull Requests
 
-If your PR fails to pass CI or needs changes based on code review, you'll most
-likely want to squash these changes into existing commits.
+If your PR fails to pass CI or needs changes based on code review, it's ok to
+add more commits stating the changes made, e.g. "Address review comments". This
+is to assist the reviewer(s) to easily detect and review the recent changes.
 
-If your pull request contains a single commit or your changes are related to the
-most recent commit, you can simply amend the commit.
+In case of small PRs, it's ok to squash and force-push (see further below)
+directly instead.
 
 ```console
+# incorporate review feedback
 $ git add .
-$ git commit --amend
-$ git push --force-with-lease $USER issue-<number>
+
+# create a fixup commit which will be merged into your (original) <commit>
+$ git commit --fixup <commit>
+$ git push $USER issue-<number>
 ```
 
-If you need to squash changes into an earlier commit, you can use:
+Be sure to add a comment to the PR indicating your new changes are ready to
+review, as Github does not generate a notification when you git push.
+
+Once the review is complete, squash and push your final commit(s):
 
 ```console
-$ git add .
-$ git commit --fixup <commit>
+# squash all commits into one
+# --autosquash will automatically detect and merge fixup commits
 $ git rebase -i --autosquash vmware/master
 $ git push --force-with-lease $USER issue-<number>
 ```
 
-Be sure to add a comment to the PR indicating your new changes are ready to
-review, as Github does not generate a notification when you git push.
-
 ### Code Style
 
 The coding style suggested by the Go community is used in `govmomi`. See the