Squash multiple commits into a single commit.
Merge all commits from a specific branch into the current branch as a single commit
$ git squash [source_branch]
Squash all commits starting with a specific commit on the current branch
$ git squash [commit]
Squash the n latest commits and commit with a message
$ git squash HEAD~[n] "[message]"
Squash the n latest commits and commit concatenating all individual messages
$ git squash --squash-msg HEAD~[n]