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Aravind Vasudevan


An inquisitive polyglot developer and Machine Learning enthusiast.


Undoing screw-ups in Mercurial

In the last three months of using Mercurial at my internship, I have screwed up a lot of times. From adding wrong files to pushing bad commits, I have done it all. So, as the end of my internship is nearing, I’m making a list of fixes that I learned during this journey.


Adding all files

Most of us have a muscle memory of doing this:

git/hg add .
git/hg commit -m "foo"
git/hg push

But if you are working on a legacy codebase which is as old as time itself, you will have to look twice for a ignore file before adding everything. Trust me on this, you don’t want to look like a halfwit who is just discovering what a version control is at your internship.

But if you have mindlessly added everything, here is how you undo it:

hg update -C

Beware: This removes all uncommitted changes. So backup your changes before you run this.

Ludicrous Changes

Sometimes we do changes that make us question our own sanity. At times like these, all we want is to revert back to the previous commit and pretend like nothing happened. Here is how you do that:

Before Commit

This is easy. you have done something ridiculous but were lucky enough to spot it out before committing. Just run this:

hg update -C

After Commit

This is easy too. you have done something ridiculous and you committed. Just run this:

hg strip 'roots(outgoing())'

After Push

This is when you should consider a doctor and another job since doing a half-assed push as an intern is the best way to get kicked out. Reverting pushed commits in Mercurial is so convoluted that you might find a million different variation of doing it on the web. Here is the one that worked for me:

hg clone -r [changeset] [repo] [new-directory] # this is much quicker than cloning it from the server
cp [repo]/.hg/hgrc [new-directory]/.hg/

Running this, you will end up with a new repo at the given changeset.


And that’s pretty much it. Hopefully, this was helpful.

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