When I run hg commit, Mercurial generates a file for my commit message that looks like this :
hg commit
HG: Enter commit message. Lines beginning with \'
Use hg commit -m "My message here". You can also set up an editor in your Mercurial.ini or ~/.hgrc file. Add the following:
hg commit -m "My message here"
Mercurial.ini
~/.hgrc
[ui] editor = /path/to/your/favorite/editor