Reading the jj changelog is fun where you see them deprecate functions, acknowledging that they perform identical purposes. Beautiful to see this simplification that benefits all users going forward.

The one that stood out in my mind:

  `jj checkout` and `jj merge` are both deprecated; use `jj new` instead to replace both of these commands in all instances.

  Rationale: jj checkout and jj merge both implement identical functionality, which is a subset of jj new. checkout creates a new working copy commit on top of a single specified revision, i.e. with one parent. merge creates a new working copy commit on top of at least two specified revisions, i.e. with two or more parents.

  The only difference between these commands and jj new, which also creates a new working copy commit, is that new can create a working copy commit on top of any arbitrary number of revisions, so it can handle both the previous cases at once. The only actual difference between these three commands is the command syntax and their name. These names were chosen to be familiar to users of other version control systems, but we instead encourage all users to adopt jj new instead; it is more general and easier to remember than both of these.