hg bookmark 
hg bookmark 
hg update 
(some commits for dev)
hg update 
(some commits for main)
hg merge 
hg bookmark -d 

hg branch 
(some commits for main)
hg branch 
(some commits for dev)
hg update main
hg merge 
hg commit

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