Fully fork a git repo?

Question

I've not quite managed to piece together what I want to know from the multitude of answers on here and blog posts, so I'm asking this question:

How do I fork a git repo such that I get all the branches & tags of the upstream?

What I've tried is:

git init
git remote add origin <ORIGIN_URL> # i.e. my repo
git remote add upstream <UPSTREAM_URL> # i.e. the repo I want to fork
git fetch upstream
git push --all origin

But that last line fails when I would expect it to work. I get this:

$ git push --all origin
No refs in common and none specified; doing nothing.
Perhaps you should specify a branch such as 'master'.
fatal: The remote end hung up unexpectedly
error: failed to push some refs to <ORIGIN_URL>

Any ideas?

EDIT:

Maybe you can think of this question as "What does GitHub actually do when you click the fork button?", as that's the behaviour I am trying to replicate.

Answer 1

Try a mirror:

git clone --mirror

This way, the remote (named origin ) is created without a namespace for branches. IOW, the refs/heads/master in the mirror corresponds exactly (and is bound to) the refs/heads/master in the origin repository.

Now just use this repository instead of original upstream repository. If you ever want to update the mirror, do something like this in it:

cd upstream-mirror.git && git --bare fetch upstream

Warning: if you ever push into your mirror, modifying the upstreams branches, the upstream repo and your mirror will diverge. and push (without -f option) will fail, to prevent that.

Mirror is actually an exact mirror of the upstream repo, with you, as its owner, having an option to modify it.

Answer 2

This is what I've come up with as the best way to do what I wanted which seems to work and gets a similar behaviour to what GitHub does:

git clone --mirror <UPSTREAM> myrepo
cd myrepo
git remote rename origin upstream
git remote add origin <MY_ORIGIN>
git push --all
git push --tags

And then tweak the .git/config to change the upstream remote to not mirror anymore as that's certainly not what I want now.