Comment 2 for bug 41435

> There is a plugin which now provides this. Called 'difftools'. There is also a similar one 'extmerge' which does merging using 3rd party tools.

"extmerge" exists only in the plugin list, it's not possible to download it.
"difftools" doesn't help too much in merging.

> Do we need to keep a bug tracker open for this?

I think yes. It's much easier to merge booth in Mercurial and in darcs.