How do I git reset –hard HEAD on Mercurial?

If you’ve not yet commited, and it sounds like you haven’t you can undo all the merge work with hg update --clean.

However, in newer mercurial’s there’s a handy command to re-merge a single file: hg resolve path/to/file.ext. From the hg help resolve:

The available actions are: ...

 4) discard your current attempt(s) at resolving conflicts and

restart
the merge from scratch: “hg resolve file…” (or “-a” for all
unresolved files)