blogc-git-receiver(1) -- a simple login shell/git hook to deploy blogc websites
===============================================================================

## SYNOPSIS

chsh -s $(command -v `blogc-git-receiver`) <user>

## DESCRIPTION

**blogc-git-receiver** provides a PaaS-like way to deploy blogc(1) websites.
When used as a login shell, it will accept git payloads, creating bare repositories
as needed, and installing a hook, that will take care of rebuilding the website each
time someone push something to the `master` branch.

The git repository must provide a `Makefile` (or a `GNUMakefile`), that should
accept the `OUTPUT_DIR` variable, and install built files in the directory pointed
by this variable.

`blogc-git-receiver` is part of `blogc` project, but isn't tied to blogc(1). Any
repository with `Makefile` that builds content and install it to `OUTPUT_DIR`
should works with `blogc-git-receiver`.

## SETUP

After creating an user (`blogc` for the examples), change its shell to
blogc-git-receiver(1):

    # chsh -s $(command -v blogc-git-receiver) blogc

Now add ssh keys to `/home/blogc/.ssh/authorized_keys`. Every key in
`authorized_keys` will be allowed to push to the git repositories, and even
create new ones.

Also, make sure to install all the dependencies required by the websites,
including a web server. `blogc-git-receiver` can't handle web server virtual hosts.

To deploy a website (e.g. blogc example repository):

    $ git clone https://github.com/blogc/blogc-example.git
    $ cd blogc-example
    $ git remote add blogc blogc@${SERVER_IP}:blogs/blogc-example.git
    $ git push blogc master

This will deploy the example to the server, creating a symlink to the built content
in `/home/blogc/repos/blogs/blogc-example.git/htdocs`. This symlink should be used
as the document root for the web server virtual host.

### Rebuild last successful build

If for some reason you want to rebuild the last successful build of a given website,
you can run its `pre-receive` hook manually in the server:

    # su -s /bin/sh - blogc
    $ cd ~/repos/blogs/blogc-example.git
    $ ./hooks/pre-receive

This should re-run the last build as if it was pushed to git.

### Setup with SELinux enabled (Fedora)

Supposing the usage of nginx as webserver, running as the `nginx` user:

    # dnf install -y nginx policycoreutils-python-utils
    # useradd -m -s $(command -v blogc-git-receiver) blogc
    # gpasswd -a nginx blogc
    # chmod -R g+rx /home/blogc
    # su -c "mkdir /home/blogc/{builds,repos}" -s /bin/sh blogc
    # semanage fcontext -a -t httpd_sys_content_t "/home/blogc/(builds|repos)(/.*)?"
    # restorecon -R -v /home/blogc
    # systemctl restart nginx

After running these commands, the machine is ready to be used.

## REPOSITORY MIRRORING

Users can rely on `blogc-git-receiver` to mirror repositories to a remote Git
repository (e.g. a free Bitbucket private repository).

Please note that the `blogc` user must be able to push to the remote repository, and
that any content manually pushed to the remote repository is overwritten by
`blogc-git-receiver`.

Some reasonable ways to allow the `blogc` user to push to the remote repository are:

- Create a password-less SSH key. The key *must* be password-less, because the push
  is automatic, and remote git hooks can't be interactive.
- Create an oauth token in the hosting service (if it supports oauth authentication
  in git, e.g. GitHub) and add it to the git URL.

The mirroring feature wont't block a `git push`, it will just raise warnings. That
means that if an error happens when mirroring the repository, the deploy will still
succeed. Users should pay attention to the git hook logs, to avoid losing data
due to repositories not being mirrored.

This feature just requires adding a remote called `mirror` to the bare repository
in the server, or creating a configuration file (~/blogc-git-receiver.ini), that is
a simple INI-style file where each repository is represented by a section and the
value of the `mirror` variable is the URL that should be used to push.

To create the configuration file (recommended):

    # su -s /bin/sh - blogc
    $ cat > ~/blogc-git-receiver.ini <<EOF
    [repo:myblog.git]
    mirror=$YOUR_GIT_MIRROR_URL
    EOF

Or to add the `mirror` remote:

    # su -s /bin/sh - blogc
    $ cd repos
    $ git init --bare myblog.git  # if not created yet
    $ cd myblog.git
    $ git remote add --mirror=push mirror $YOUR_GIT_MIRROR_URL

Both examples assume that your repository is named `myblog.git`.

### Caveats of repository mirroring with SSH

The authentication must be done with a password-less SSH key created by the `blogc`
user.

As the `git push --mirror` call is automated, users must disable SSH strict host
checking in SSH's `~/.ssh/config` file:

    Host bitbucket.org
        StrictHostKeyChecking no

The example uses `bitbucket.org` as remote host, that should be changed if needed.

To change this file, users must login with `/bin/sh` or any other "real" shell,
as `root`:

    # su -s /bin/sh - blogc

### Push to mirror manually

If for some reason you want to push the repository of a given website to remote
mirror, you can run its `post-receive` hook manually in the server:

    # su -s /bin/sh - blogc
    $ cd ~/repos/blogs/blogc-example.git
    $ ./hooks/post-receive

WARNING: If you push manually and your server's repository is empty, you'll clean
your mirror repository.

## ENVIRONMENT VARIABLES

`blogc-git-receiver` will export an environment variable called `BLOGC_GIT_RECEIVER`
when calling `gmake` to build websites. This variable can be used to enable building
of content that should only be built when running in production environment, for
example.

## BUGS

Please report any issues to: <https://github.com/blogc/blogc>

## AUTHOR

Rafael G. Martins &lt;<rafael@rafaelmartins.eng.br>&gt;

## SEE ALSO

blogc(1), git(7), chsh(1), su(1), make(1)