The "merge this merge request manually" text and instructions in an MR are sometimes misleading and wrong
Problem to solve
Pretty much every MR has this little note and link (I've checked multiple states).
You can merge this merge request manually using the command line
The linked instructions looks like this.
But, this note is misleading and provides incorrect instructions in the case of an MR that needs to be rebased. I get that the text doesn't say "rebase this MR manually", but it's provided as a footnote, almost, in context with the Rebase button. My team mates often try following this instruction when they have an MR that won't automatically rebase.
This is when using the "Merge commit with semi-linear history" merge method.
I suspect that those instructions are also incorrect for the "Fast-forward merge" merge method (I haven't tried, but I bet those instructions are static and do not update to use --ff-only.
Proposal
You should stop showing these instructions or make them context sensitive (based on your current merge settings).