hg config --edit

[Matt Mackall]

I've just pushed some changes that do the following:

$ hg ci
abort: no username supplied
(use "hg config --edit" to set your username)

$ hg config --edit

..which launches your editor with the following text prepopulated:

# example config (see "hg help config" for more info)

[ui]
# set this to your full email address
username =

[extensions]
# uncomment these lines to enable some popular extensions
# (see "hg help extensions" for more info)
# pager =
# progress =
# color =


Please try it out. 

-- 
Mathematics is the supreme nostalgia of our time.