sync-up

Sync.up

A simple system to keep a repository in sync with an upstream repository and then push any changes to a separate repository. I use this to clone upstream repositories from Github, since Microsoft bought it, updating a local clone of a repo and then pushing those changes to an online Git hosting service.

Manual

To use sync.up manually:

1. Find a repo on Github that you want to mirror. From now on, this repo is known as upstream.
2. Create an empty repo on some other Git hosting service like http://gitlab.com, http://notabug.org, or your own private server.
3. Clone the empty repo from your remote host: $ git clone git@github.com:notklaatu/foo.git foo.git
4. Add the upstream URL to your local clone: $ git remote add upstream git@github.com:notklaatu/foo.git
5. The first time you push to your empty remote, you must do so manually, so that you are telling the remote that you are sending it a new branch: $ git push -u upstream master
6. After that, you can use sync.up to pull from upstream into your local clone and push to your remote: $ ./sync.up foo.git

Automation

More likely, you want sync.up to be automated. You can do this with a simple cron job. Edit your crontab with the crontab -e command and add either:

@weekly path/to/sync.up path/to/foo.git

or

0 0 * * 0 path/to/sync.up path/to/foo.git

For a weekly update.

See http://crontab.guru for more crontab syntax.

Known issues

There are some quirks when mirroring a repository. Here are some things that might happen, and how to fix them:

Untracked branch on remote

If you use an import tool to import a repo from Github into your new remote, then sync.up works right away. However, if you create an empty repo on a remote server, then that repo has no knowledge of what your local repo contains. That's why you have to do your first push manually:

$ git push -u upstream master

The -u option tells your remote Git repo (upstream, in this example) to start tracking the master branch. If you do not do this before attempting to use sync.up, then sync.up fails. All is not lost; just do the manual push -u and then you can use sync.up from then on.

Mismatched names for "master" branch

If the upstream repository is not called master, then sync.up fails.

You can fix this by defining the branch names involved. The easiest way to do this is to edit the .git/config file in your repository directly. Assuming the upstream "master" branch is called develop but your local copy is called master, you see this in your config file:

...
[remote "origin"]
    url = git@gitlab.com:notklaatu/grav.git
    fetch = +refs/heads/*:refs/remotes/origin/*
[remote "upstream"]
url = git@github.com:getgrav/grav.git
fetch = +refs/heads/*:refs/remotes/origin/*

Set the upstream branch to develop:

[branch "develop"]
    remote = upstream
merge = refs/heads/develop

And set your local master branch to master:

[branch "master"]
    remote = origin
    merge = refs/heads/master

Bugs

If you find other issues, report them to klaatu@member dot fsf dot org.