Comment by drostie

In other words, in Git, a branch is just a named pointer to a particular revision. In Hg, these are called 'bookmarks' and they work exactly how you're imagining; and there is an immutable sort of bookmark that is called a 'tag' (bookmarks can be repointed; tags cannot). By creating a new head (i.e. branching) and naming that new head with a bookmark, you do exactly what `git branch` does.

Mercurial also supports an autonaming of revisions which automatically applies to all child revisions, too: these are meant to be independent lines of development with their its own head revision, and are called 'named branches'; that is what `hg branch` does. The problem that you're identifying (and that I agree is counterintuitive!) is that these names become part of the commits themselves and therefore public knowledge. Mercurial warns you when you `hg branch` that this is happening and says "did you want a bookmark?" but does not tell you, e.g., "to undo what you just did, type `hg branch default`."