title: Can't determine if a branch has been merged when squash is used
body: <p>My team uses github and sourcetree to manage our workflow. We've recently started trying out github's squash merge feature. We really like how it keeps our work history tidy, and essentially has a single commit per PR.</p>
  
  <p>One of the unexpected downsides of using squash commits is that it's difficult to tell when a local branch can be deleted. My entire team seems to manage their local branches based on being able to visually see in the commit graph that it's been merged, and every few days we'll go through our local branches one by one seeing if they've been merged, and then remove it locally if it has. Enabling squash merging removes this visualization and makes it difficult for us to tell if the branch has been merged.</p>
  
  <p>We'd really like to use the squash commit feature, but we need a reliable way to determine if a branch has been merged and is safe to be deleted locally. Are there any good ways that we haven't thought of to achieve this?</p>