+[git]: http://git.or.cz/
+
+Ikiwiki can run as a git `post-update` hook to update a wiki
+whenever commits come in. When running as a [[cgi]],
+ikiwiki automatically commits edited pages, and uses the
+git history to generate the [[RecentChanges]] page.
+
+Normally you can just follow the instructions in [[setup]] to create
+the git repositories and get started. To understand the details, read on.
+
+## git repository setup
+
+[[!img wiki_edit_flow.svg size=490x align=right]]
+
+The suggested setup for git has a bare repository, and various
+working clones (with working directories). The bare
+repository is pushed to and pulled from the various working clones.
+
+One of the clones is special; it is the srcdir
+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) clones are meant for you to work
+on, and commit to, changes should then be pushed to the bare root
+repository.
+
+Using three or more 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.
+
+## 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 be pushed 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`
+[[ikiwiki/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 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 --gettime` and
+you should be good to go. (You only need the slow `--gettime` option
+the first time you run setup.) Use standard git commands to handle
+pulling from and pushing to the server. **Note**: 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`. You could use git's `post-merge` hook
+to automate that command.
+
+## Using ikiwiki with Gerrit
+
+[Gerrit Code Review](https://code.google.com/p/gerrit/) manages a set of Git
+repositories and provides a web interface to review and merge commits. You can
+configure ikiwiki to work with a Gerrit-managed repository, allowing you to
+review and merge commits to your wiki.
+
+First, create your initial wiki repository with Gerrit. On the server, as the
+user that will own the wiki, clone that repository to create a working
+directory for ikiwiki, such as /srv/wiki/ikiwiki-checkout. Create a setup file
+and target directory as usual, referencing that working directory path, and
+creating a post-update hook in Gerrit's repository. You'll need to set
+appropriate permissions on the hook directory for the repository so that the
+user running ikiwiki can compile and install the post-update hook. Also note
+that you must disable web editing by disabling the editpage plugin, and you
+must not enable any other plugin that commits to the repository, since ikiwiki
+will not have permission to push to the repository. (Allowing web edits to
+have such permission would bypass Gerrit's code review, defeating the purpose.)
+
+Gerrit does not run per-repository hooks, such as the post-update hook ikiwiki
+installs to update the wiki after pushes. However, Gerrit has site-wide hooks,
+including a ref-updated hook that runs whenever a ref changes. You can use
+that hook to trigger ikiwiki's post-update hook. The following script,
+installed as Gerrit's ref-updated hook, will run the post-update hook on any
+repository that has a "gerrit-run-post-update-hook" file in it:
+
+ #!/bin/sh
+ if [ -e "$GIT_DIR/gerrit-run-post-update-hook" ] ; then
+ exec "$GIT_DIR/hooks/post-update"
+ fi
+
+Then just create gerrit-run-post-update-hook in the wiki repository, run
+ikiwiki --setup on the setup file, add your wiki to /etc/ikiwiki/wikilist, and
+start reviewing and committing wiki changes via Gerrit.