minor: A bit more wikilinks.

[ikiwiki] / doc / rcs / git.mdwn

[[!meta title="Git"]]

[Git][git] is a distributed revison control system originally developed for
the Linux kernel. Ikiwiki supports storing a wiki in git.

[git]: http://git.or.cz/

Ikiwiki can run as a `post-update` hook to update a wiki whenever commits
come in. When running as a [[cgi]] with Git, ikiwiki automatically
commits edited pages, and uses the Git history to generate the
[[RecentChanges]] page.

## git repository setup

The suggested setup for git is a set of repositories setup like a
shallow, single level tree, with a bare repository (meaning that it
does not have a working tree checked out) at the root, and various
working clones (with working directories) as leaf nodes.  The root
(bare) repository is meant to be pushed to and pulled from the various
working clones.

One of the leaf node clone repositories is special; it has working
directory which is used to compile the wiki, and is also used by the
[[cgi]] to commit changes made via the web interface. It is special
since the `post-update` hook for the bare root repository is used to
trigger an update of this repository, and then an ikiwiki refresh
updates the published  wiki itself.

The other (optional) leaf node repositories are meant for you to work
on, and commit to, changes should then be pushed to the bare root
repository.  In theory, you could work on the same leaf node repository
that ikiwiki uses to compile the wiki from, and the [[cgi]] commits
to, as long as you ensure that permissions and ownership don't hinder
the working of the [[cgi]]. This can be done, for example, by using
ACL's, in practice, it is easier to just setup separate clones for
yourself.

So, to reiterate, when using Git, you probably want to set up three
repositories:

* The root repository. This should be a bare repository (meaning that
  it does not have a working tree checked out), which the other
  repositories will push to/pull from.  It is a bare repository, since
  there are problems pushing to a repository that has a working
  directory. This is called _repository_ in [[ikiwiki-makerepo]]'s
  manual page. Nominally, this bare repository has a `post-update` hook
  that either is or calls ikiwiki's git wrapper, which changes to the
  working directory for ikiwiki, does a `git pull`, and refreshes ikiwiki
  to regenerate the wiki with any new content. The [[setup]] page describes
  how to do this.

* The second repository is a clone of the bare root repository, and
  has a working tree which is used as ikiwiki's srcdir for compiling
  the wiki. **Never** push to this repository. When running as a
  [[cgi]], the changes are committed to this repository, and pushed to
  the master repository above. This is called _srcdir_ in
  [[ikiwiki-makerepo]]'s manual page.

* The other (third, fourth, fifth, sixth -- however many pleases you)
  repositories are also clones of the bare root repository above --
  and these have a working directory for you to work on. Use either
  the `git` transport (if available), or `ssh`. These repositories may
  be on remote machines, your laptop, whereever you find convenient to
  hack on your wiki. you can commit local changes to the version on
  the laptop, perhaps while offline. Any new content should be pushed to the
  bare master repository when you are ready to publish it, and then
  the post-update hook of the bare repository will ensure that the
  ikiwiki's source directory is updated, and the ikiwiki refreshed
  with the new content.

Using three or more of repositories isn't the most obvious set up, but
it works the best for typical ikiwiki use. [[ikiwiki-makerepo]] can
automate setting this up for the common case where there is no
pre-existing wiki. [[tips/Laptop_wiki_with_git]] describes a different
way to set up ikiwiki and git.

It is **paramount** that you **never** push to the non-bare repository
([this FAQ entry explains why](http://git.or.cz/gitwiki/GitFaq#head-b96f48bc9c925074be9f95c0fce69bcece5f6e73)).
Instead, clone the bare repository as mentioned above, and push
**only** to the bare repository.

The ikiwiki `post-update` hook should be put in the bare repository.

## git repository with multiple committers

It can be tricky to get the permissions right to allow multiple people to
commit to an ikiwiki git repository. As the [[security]] page mentions,
for a secure ikiwiki installation, only one person should be able to write
to ikiwiki's srcdir. When other committers make commits, their commits
should go to the bare repository, which has a `post-update` hook that uses
ikiwiki to pull the changes to the srcdir.

One setup that will work is to put all committers in a group (say,
"ikiwiki"), and use permissions to allow that group to commit to the bare git
repository. Make both the post-update hook and ikiwiki.cgi be setgid
to the group, as well as suid to the user who admins the wiki. The
`wrappergroup` [[setup_file_option|usage]] can be used to make the wrappers
be setgid to the right group. Then the srcdir, including its git
repository, should only be writable by the wiki's admin, and *not* by the
group. Take care that ikiwiki uses a umask that does not cause files in
the srcdir to become group writable. (umask 022 will work.)

## git repository with untrusted committers

By default, anyone who can commit to the git repository can modify any file
on the wiki however they like. A `pre-receive` hook can be set up to limit
incoming commits from untrusted users. Then the same limits that are placed
on edits via the web will be in effect for commits to git for the users.
They will not be allowed to edit locked pages, they will only be able to
delete pages that the [[plugins/remove]] configuration allows them to
remove, and they will only be allowed to add non-page attachments that the
[[plugins/attachment]] configuration allows.

To enable this, you need to set up the git repository to have multiple
committers. Trusted committers, including the user that ikiwiki runs as, 
will not have their commits checked by the `pre-receive` hook. Untrusted
committers will have their commits checked. The configuration settings to
enable are `git_test_receive_wrapper`, which enables generation of a
`pre-receive` hook, and `untrusted_committers`, which is a list of
usernames of the untrusted committers.

Note that when the `pre-receive` hook is checking incoming changes, it
ignores the git authorship information, and uses the username of the unix
user who made the commit. Then tests including the `locked_pages` [[PageSpec]]
are checked to see if that user can edit the pages in the commit.

You can even set up an [[anonymous_user|tips/untrusted_git_push]], to allow
anyone to push changes in via git rather than using the web interface.

## Optionally using a local wiki to preview changes

When working on the "working clones" to add content to your wiki,
it is common (but optional) practice to preview your changes using a
private wiki on the local host before publishing the updates by
sending it to the root repository. If you do want to setup a private
wiki, you will have to have another setup file and and an ikiwiki
installation on your local machine. You will need all the packages
this implies -- a web server, git, ikiwiki, etc.  However, there is a
_caveat_: by default, ikiwiki pulls and pushes from `origin`. This is
not ideal for the working clones on the local machine, since you might
go through several iterations of a page before pushing to the bare
root of the repository tree (and thus publishing it on your public wiki).
You do not want the action of refreshing the local wiki in order to
review your work to accidentally publish the
contents before you are ready. In order to prevent the git push that
is the normal behaviour of ikiwiki, set the configuration of the local wiki:

      gitorigin_branch => "",
      ## git post-commit wrapper
      git_wrapper => "/working/dir/.git/hooks/post-commit",

Then just committing should refresh the private ikiwiki on the local
host.  Now just run `ikiwiki -setup localwiki.setup -getctime` and
you should be good to go. (You only need the slow `-getctime` option
the first time you run setup.)  Use standard git commands to handle
pulling from and pushing to the server.  **Note**: Currently, after
pulling changes from the bare root repository, you will need to
manually update the local wiki, with a command such as `ikiwiki
-setup localwiki.setup -refresh`. This is because git 1.5.4 doesn't
have a hook that is run locally after pulling changes. Newer
versions of git will have a `post-merge` hook that should work for
this purpose.

## Fix for error on git pull origin

Error message when running git pull origin:

    You asked me to pull without telling me which branch you
    want to merge with, and 'branch.master.merge' in
    your configuration file does not tell me either.  Please
    name which branch you want to merge on the command line and
    try again (e.g. 'git pull <repository> <refspec>').
    See git-pull(1) for details on the refspec.
    
    If you often merge with the same branch, you may want to
    configure the following variables in your configuration
    file:
    
        branch.master.remote = <nickname>
        branch.master.merge = <remote-ref>
        remote.<nickname>.url = <url>
        remote.<nickname>.fetch = <refspec>
    
    See git-config(1) for details.

The solution is to run this command in your srcdir:

    git config branch.master.remote origin