ikiwiki/doc/todo/applydiff_plugin.mdwn

[[!tag wishlist done]]

[[!toc ]]

Summary
=======

Allow a user to apply an arbitrary diff, in order to modify a given
page (or, even better, a given set of pages).

Rationale
=========

To edit intensively an ikiwiki-powered website can quickly get
annoying for anybody meeting enough of the following conditions:

* living mainly offline
* having no commit access to the RCS backing up the site (BTW, please
  note I can send my ssh public key to anyone who asks for, free of
  charges)
* hating web-browsers and despising textareas
* loving in his/her own preferred `$EDITOR`

... and when one gathers all of these defaults, she/he is on her/his
way to get mad. Soon.

Before it's too late, some dareful ones dream of the following
playflow:

1. Go online.
1. Update local working copy.
1. Go offline.
1. `$EDITOR` : write, report, answer, propose
1. Go online.
1. Update local working copy (and optionally fix conflicts between
   local changes and remote ones).
1. Generate a diff.
1. Use a web-browser to paste the diffs (or better, upload them into
   a form) somewhere on the wiki, and click "Apply".
1. git pull (to reflect locally the fact that the diff has been
   applied to the remote repo)
1. Go offline.

(This is for sure a bit theoretical: the ones who dream of this would
actually insert various steps about branching, merging and rebasing
random stuff.)

Design
======

This has to be thought very carefully, to avoid one to apply diffs to
pages he/she is not allowed to edit. Restricting a given diff to
modify only *one* page may be easier.

Implementation
==============

Also see [[joey]]'s idea on [[users/xma/discussion]], to allow (filtered) anonymous push to this wiki's repository.

> Ideally the filtering should apply the same constraints on what's pushed
> as are applied to web edits. So locked pages can't be changed, etc.
> 
> That could be accomplished by making the git pre-receive hook be a
> ikiwiki wrapper. A new `git_receive_wrapper` config setting could cause
> the wrapper to be generated, with `$config{receive}` set to true.
> 
> When run that way, ikiwiki would call `rcs_receive`. In the case of git,
> that would look at the received changes as fed into the hook on stdin,
> and use `parse_diff_tree` to get a list of the files changed. Then it
> could determine if the changes were allowed.
> 
> To do that, it should first look at what unix user received the
> commit.  That could be mapped directly to an ikiwiki user. This would
> typically be an unprivelidged user (that was set up just to allow
> anonymous pushes), but you might also want to set up
> separate users who have fewer limits on what they can push. And, of
> course, pushes from the main user, who owns the wiki, would not be
> checked at all. So, let's say `$config{usermap}` is a hash, something
> like `{usera => "wikiusera", userb => "wikiuserb"}`, and pushes from
> users not in the hash are not checked.
> 
> Then it seems like it would want to call `check_canedit` to test if an
> edit to each changed page is allowed. Might also want to call
> `check_canattach` and `check_canremove` if the attach and remove plugins
> are enabled. All three expect to be passed a CGI and a CGI::Session
> object, which is a bit problimatic here. So dummy the objects up? (To call
> `check_canattach` the changed attachment would need to be extracted to a
> temp file for it to check..)
> 
> If a change is disallowed, it would print out what was disallowed, and
> exit nonzero. I think that git then discards the pushed objects (or maybe
> they remain in the database until `git-gc` .. if so, that could be used
> to DOS by uploading junk, so need to check this point).
> 
> Also, I've not verified that the objects have been recieved already when
> whe pre-receive hook is called. Although the docs seem to say that is the
> case. --[[Joey]]

>> Update: The git pre-receive hook stuff is written, and seems to work.
>> I think it makes more sense than using diffs, and so think this todo
>> could probably be closed.
>> --[[Joey]]

>>> I agree, closing this. I really prefer this solution to the one I was
>>> initially proposing.
>>> Is this pre-receive hook already enabled on ikiwiki.info?
>>> If not, do you plan to enable it at some point?
>>> --[[intrigeri]]

>>>> [[news/git_push_to_this_wiki]] gave me the answer. Well done! --[[intrigeri]]