Mercurial Tips

1. Trashcan - [from the docs] The shelve tool is very conservative with your source and patch files. Before it modifies any file it makes a backup under .hg/Trashcan. This trashcan can be emptied by running the purge dialog from the Workbench Repository –> Purge menu option.

Mercurial: abort: uncommitted local changes

If you're using TortoiseHg Workbench: go to Repository --> Terminal.
Otherwise simply open a console and cd to the root directory of your repository.
Type: 
 
> hg update --clean -r tip

That should solve the problem.
Thanks to Mike here.

Forgot to Change Mercurial's Commit Comment?

If you're using TortoiseHg (my version is 2.9.2) and it's the last thing you did (the commit), then you can simply go to Repository --> Rollback/Undo. What you need is the Undo and to preserve the changed files in the workspace. Follow the instructions then and you're set!