Question: I am currently using TortoiseHg (Mercurial) and accidentally committed an incorrect commit message. How do I go about editing this commit message in the repository?

Answer: 
Good news: hg 2.2 [just added](https://www.mercurial-scm.org/wiki/WhatsNew/Archive#Mercurial_2.2_.282012-05-01.29) git like `--amend` option.

and in tortoiseHg, you can use "Amend current revision" by select black arrow on the right of commit button 

![a](https://i.stack.imgur.com/xkoaU.jpg)
Rollback-and-reapply is realy simple solution, but it can help only with the last commit. Mercurial Queues is much more powerful thing (note that you need to [enable Mercurial Queues Extension](http://mercurial.selenic.com/wiki/MqExtension) in order to use "hg q\*" commands).