@startuml

node "Maintainer's remote" as remote_a
node "Contributor's remote" as remote_b
node "Maintainer's local" as local_a
node "Contributor's local" as local_b

actor Maintainer as a
actor Contributor as b

remote_a <----> local_a
remote_b <----> local_b

remote_a ----> local_b : "Fetch upstream"
remote_b ----> local_a : "Merge PR"

local_a -- a
local_b -- b

@enduml