Squash commit tooltip needs improved text
**Problem**
The **Squash commits** checkbox currently has tooltip text of "About this feature". This provides no useful information to the user.
**Suggestions**
1. Change the text to "Squash all commits into a single commit on merge."
1. Add to the tooltip a link to https://docs.gitlab.com/ee/user/project/merge_requests/squash_and_merge.html
issue