+By design, Git backend uses a "master-clone" repository pair approach in contrast
+to the single repository approach (here, _clone_ may be considered as the working
+copy of a fictious web user). Even though a single repository implementation is
+possible, it somewhat increases the code complexity of backend (I couldn't figure
+out a uniform method which doesn't depend on the prefered repository model, yet).
+By exploiting the fact that the master repo and _web user_'s repo (`srcdir`) are all
+on the same local machine, I suggest to create the latter with the "`git clone -l -s`"
+command to save disk space.
+
+Note that, as a rule of thumb, you should always put the rcs wrapper (`post-update`)
+into the master repository (`.git/hooks/`) as can be noticed in the Git wrappers of
+the sample [[ikiwiki.setup]].
+
+## [[Mercurial]]
+
+The Mercurial backend is still in a early phase, so it may not be mature
+enough, but it should be simple to understand and use.
+
+As Mercurial is a distributed RCS, it lacks the distinction between
+repository and working copy (every wc is a repo).
+
+This means that the Mercurial backend uses directly the repository as
+working copy (the master M and the working copy W described in the svn
+example are the same thing).
+
+You only need to specify 'srcdir' (the repository M) and 'destdir' (where
+the HTML will be generated).
+
+Master repository M.
+
+RCS commit from the outside are installed into M.
+
+M is directly used as working copy (M is also W).
+
+HTML is generated from the working copy in M. rcs_update() will update
+to the last committed revision in M (the same as 'hg update').
+If you use an 'update' hook you can generate automatically the HTML
+in the destination directory each time 'hg update' is called.
+
+CGI operates on M. rcs_commit() will commit directly in M.
+
+If you have any question or suggestion about the Mercurial backend
+please refer to [Emanuele](http://nerd.ocracy.org/em/)
+
+## [[tla]]
+
+## rcs
+
+There is a patch that needs a bit of work linked to from [[todo/rcs]].
+
+## [Monotone](http://monotone.ca/)
+
+In normal use, monotone has a local database as well as a workspace/working copy.
+In ikiwiki terms, the local database takes the role of the master repository, and
+the srcdir is the workspace. As all monotone workspaces point to a default
+database, there is no need to tell ikiwiki explicitly about the "master" database. It
+will know.
+
+The patch currently supports normal committing and getting the history of the page.
+To understand the parallel commit approach, you need to understand monotone's
+approach to conflicts:
+
+Monotone allows multiple micro-branches in the database. There is a command,
+`mtn merge`, that takes the heads of all these branches and merges them back together
+(turning the tree of branches into a dag). Conflicts in monotone (at time of writing)
+need to be resolved interactively during this merge process.
+It is important to note that having multiple heads is not an error condition in a
+monotone database. This condition will occur in normal use. In this case
+'update' will choose a head if it can, or complain and tell the user to merge.
+
+For the ikiwiki plugin, the monotone ikiwiki plugin borrows some ideas from the svn ikiwiki plugin.
+On prepedit() we record the revision that this change is based on (I'll refer to this as the prepedit revision). When the web user
+saves the page, we check if that is still the current revision. If it is, then we commit.
+If it isn't then we check to see if there were any changes by anyone else to the file
+we're editing while we've been editing (a diff bewteen the prepedit revision and the current rev).
+If there were no changes to the file we're editing then we commit as normal.