[gorgoiler]

They aren’t all the same thing. A diff (or patch) is a change to the code that’s not tied to the history in any place. Linux kernel patches and Meta diffs are like this.

Pull Requests and Merge Requests are more complicated, and the unit of change is a branch. Many people reject this workflow because ultimately a branch of commits can be summed to one single diff and that’s the only thing that matters in the wider project, outside of your private branches on your personal machine.

GitLab doesn’t support anything other than merging hence the name. Most people who prefer linear history will never merge. Instead they’ll land their change on the tip of the branch, each developer taking it in turns to advance the linear history one step at a time.

I don’t know about changelists or change requests.

[tomjakubowski]

No, Gitlab does support other integration workflows, including one which requires MRs be rebased and fast-forwards them onto main without a merge commit.

[Jason_Gibson]

A changelist is most generally a Perforce term (and as may the case for Google, a similar concept). In the Perforce Helix Core (what the "Perforce Server" is currently called), changelists are increasing integers that mark units of atomic change. Changelists can contain committed work, pending work, or shelved work (a shelf is un-committed work that resides server-side). Shelves are often how code review is done since the file content and metadata is available outside of the author's computer.