It looks like hg out --patch or hg out -p is a good way to see what code is pushed out to the repo (when it is pushed)... but the diff is in text format. Is there a way to make it use kdiff3 as well?
hg outgoing --patch shows the changes in each changeset separately, which probably isn't what you want if you're looking for a visual representation. You more likely want the GUI equivalent of hg diff -r your_latest_changeset -r remote_servers_latest_changeset where the latest changesets are the respective tip revisions if you're not using named branches. You can get that in your favorite GUI using the extdiff extension yielding a final command like:
hg extdiff -p kdiff3 -r your_latest_changeset -r remote_servers_latest_changeset
来源：https://stackoverflow.com/questions/3209372/how-to-let-mercurial-show-hg-out-patch-diff-as-visual-diff