hg bookmark <bookmark_main>
hg bookmark <bookmark_dev>
hg update <bookmark_dev>
(some commits for dev)
hg update <bookmark_main>
(some commits for main)
hg merge <bookmark_dev>
hg bookmark -d <bookmark_dev>

hg branch <main_branch>
(some commits for main)
hg branch <dev_branch>
(some commits for dev)
hg update main
hg merge <dev_branch>
hg commit

#at changeset 11
hg update 10
(some commit) #now at 12
hg merge 11
hg commit #now at 13