Commits contain tangible units of progress toward the project’s goal. Each commit is indeed a pace in the project road map. In the ideal world, all commits are self-sufficient and do not require any modification after they are submitted into a repository. However, in the real world, this is not the case all the time! For example, after submitting we may find the commit message is not clear enough or it does not include all pieces of information. For such situations, Git envisioned a list of actions to update history:
Squash ...
