Attached is a silly script to create a conflict on a temporary
repository.  The script creates 3 folders in the current directory:

- hacker-repo: the folder where one hacker is working,
- hacker2-repo: the folder where another hacker is working,
- server-hosted-repo: the "central repository" where both hackers
  update from and commit to.

The script runs the following operations:

- create the central repository,
- make the first hacker commit a one-line file,
- make the second hacker update this file and commit the changes,
- make the first hacker update the file without updating from the
  central repository first.

(Some of these operations could probably have been expressed in terms
of vc commands; apologies for not taking the time to do so.)

From there one can start emacs -Q to observe the conflict:

$ emacs -Q hacker-repo
C-x v +

That gets me a log buffer from vc saying:

> Running "git pull --stat"...
> From ../server-hosted-repo
>  * branch            master     -> FETCH_HEAD
> Auto-merging README
> CONFLICT (content): Merge conflict in README
> Automatic merge failed; fix conflicts and then commit the result.

And indeed, visiting the README, I see conflict markers, and the
Smerge minor mode enabled (see attached screenshot).

C-h b tells me that C-c ^ E runs smerge-ediff, which spawns Ediff's
3-window merge UI.