How to set "hg diff" output shows in gvim?

I use mercurial and I want to see modified change in Vim or GVim. Normally there is hg diff which show the modified changes in diff format. but I want to see it in Vim as the original version and modified version side-by-side.

I try extdiff in ExtdiffExtension but it doesn't work and gvim open some blank file.

I know there is gvim -d localfile otherfile but I don't know how to config mercurial.