Add a build_affected hook so trail doesn't have to inject

[git.ikiwiki.info.git] / doc / plugins / write.mdwn

diff --git a/doc/plugins/write.mdwn b/doc/plugins/write.mdwn
index abcabbdc39e43871af4b491b47b1540fda99a34f..d62ab6e63f21dcc4f1c026f5751ca7403755dcfd 100644 (file)
--- a/doc/plugins/write.mdwn
+++ b/doc/plugins/write.mdwn
@@ -1,10 +1,86 @@
-Ikiwiki's plugin interface allows all kinds of useful [[plugins]] to be
+lkiwiki's plugin interface allows all kinds of useful [[plugins]] to be

 written to extend ikiwiki in many ways. Despite the length of this page,
 it's not really hard. This page is a complete reference to everything a
 plugin might want to do. There is also a quick [[tutorial]].
 
 written to extend ikiwiki in many ways. Despite the length of this page,
 it's not really hard. This page is a complete reference to everything a
 plugin might want to do. There is also a quick [[tutorial]].
 

+[[!template id="note" text="""
+Ikiwiki is a compiler
+
+One thing to keep in mind when writing a plugin is that ikiwiki is a wiki
+*compiler*. So plugins influence pages when they are built, not when they
+are loaded. A plugin that inserts the current time into a page, for
+example, will insert the build time.
+
+Also, as a compiler, ikiwiki avoids rebuilding pages unless they have
+changed, so a plugin that prints some random or changing thing on a page
+will generate a static page that won't change until ikiwiki rebuilds the
+page for some other reason, like the page being edited.
+
+The [[tutorial]] has some other examples of ways that ikiwiki being a
+compiler may trip up the unwary.
+"""]]
+

 [[!toc levels=2]]
 
 [[!toc levels=2]]
 

+## Highlevel view of ikiwiki
+
+Ikiwiki mostly has two modes of operation. It can either be running
+as a compiler, building or updating a wiki; or as a cgi program, providing
+user interface for editing pages, etc. Almost everything ikiwiki does
+is accomplished by calling various hooks provided by plugins.
+
+### compiler
+
+As a compiler, ikiwiki starts by calling the `refresh` hook. Then it checks
+the wiki's source to find new or changed pages. The `needsbuild` hook is
+then called to allow manipulation of the list of pages that need to be
+built. 
+
+Now that it knows what pages it needs to build, ikiwiki runs two
+compile passes. First, it runs `scan` hooks, which collect metadata about
+the pages. Then it runs a page rendering pipeline, by calling in turn these
+hooks: `filter`, `preprocess`, `linkify`, `htmlize`, `indexhtml`,
+`pagetemplate`, `sanitize`, `format`.
+
+After all necessary pages are built, it calls the `change` hook. Finally,
+if a page is was deleted, the `delete` hook is called, and the files that
+page had previously produced are removed.
+
+### cgi
+
+The flow between hooks when ikiwiki is run as a cgi is best illustrated by
+an example.
+
+Alice browses to a page and clicks Edit.
+
+* Ikiwiki is run as a cgi. It assigns Alice a session cookie, and,
+  by calling the `auth` hooks, sees that she is not yet logged in.
+* The `sessioncgi` hooks are then called, and one of them,
+  from the [[editpage]] plugin, notices that the cgi has been told "do=edit".
+* The [[editpage]] plugin calls the `canedit` hook to check if this
+  page edit is allowed. The [[signinedit]] plugin has a hook that says not:
+  Alice is not signed in.
+* The [[signinedit]] plugin then launches the signin process. A signin
+  page is built by calling the `formbuilder_setup` hook.
+
+Alice signs in with her openid.
+
+* The [[openid]] plugin's `formbuilder` hook sees that an openid was
+  entered in the signin form, and redirects to Alice's openid provider.
+* Alice's openid provider calls back to ikiwiki. The [[openid]] plugin
+  has an `auth` hook that finishes the openid signin process.
+* Signin complete, ikiwiki returns to what Alice was doing before; editing
+  a page.
+* Now all the `canedit` hooks are happy. The [[editpage]] plugin calls
+  `formbuilder_setup` to display the page editing form.
+
+Alice saves her change to the page.
+
+* The [[editpage]] plugin's `formbuilder` hook sees that the Save button
+  was pressed, and calls the `checkcontent` and `editcontent` hooks.
+  Then it saves the page to disk, and branches into the compiler part
+  of ikiwiki to refresh the wiki.
+

 ## Types of plugins
 
 Most ikiwiki [[plugins]] are written in perl, like ikiwiki. This gives the
 ## Types of plugins
 
 Most ikiwiki [[plugins]] are written in perl, like ikiwiki. This gives the


@@ -19,7 +95,7 @@ that can be fleshed out to make a useful plugin.
 `IkiWiki::Plugin::pagecount` is another simple example. All perl plugins
 should `use IkiWiki` to import the ikiwiki plugin interface. It's a good
 idea to include the version number of the plugin interface that your plugin
 `IkiWiki::Plugin::pagecount` is another simple example. All perl plugins
 should `use IkiWiki` to import the ikiwiki plugin interface. It's a good
 idea to include the version number of the plugin interface that your plugin

-expects: `use IkiWiki 2.00`.
+expects: `use IkiWiki 3.00`.

 
 An external plugin is an executable program. It can be written in any
 language. Its interface to ikiwiki is via XML RPC, which it reads from
 
 An external plugin is an executable program. It can be written in any
 language. Its interface to ikiwiki is via XML RPC, which it reads from


@@ -31,16 +107,20 @@ they're the same as far as how they hook into ikiwiki. This document will
 explain how to write both sorts of plugins, albeit with an emphasis on perl
 plugins.
 
 explain how to write both sorts of plugins, albeit with an emphasis on perl
 plugins.
 

-## Considerations
+## Plugin interface

 
 

-One thing to keep in mind when writing a plugin is that ikiwiki is a wiki
-*compiler*. So plugins influence pages when they are built, not when they
-are loaded. A plugin that inserts the current time into a page, for
-example, will insert the build time. Also, as a compiler, ikiwiki avoids
-rebuilding pages unless they have changed, so a plugin that prints some
-random or changing thing on a page will generate a static page that won't
-change until ikiwiki rebuilds the page for some other reason, like the page
-being edited.
+To import the ikiwiki plugin interface:
+
+       use IkiWiki '3.00';
+
+This will import several variables and functions into your plugin's
+namespace. These variables and functions are the ones most plugins need,
+and a special effort will be made to avoid changing them in incompatible
+ways, and to document any changes that have to be made in the future.
+
+Note that IkiWiki also provides other variables and functions that are not
+exported by default. No guarantee is made about these in the future, so if
+it's not exported, the wise choice is to not use it.

 
 ## Registering plugins
 
 
 ## Registering plugins
 


@@ -55,8 +135,8 @@ plugin, and a "call" parameter, which tells what function to call for the
 hook.
 
 An optional "last" parameter, if set to a true value, makes the hook run
 hook.
 
 An optional "last" parameter, if set to a true value, makes the hook run

-after all other hooks of its type. Useful if the hook depends on some other
-hook being run first.
+after all other hooks of its type, and an optional "first" parameter makes
+it run first. Useful if the hook depends on some other hook being run first.

 
 ## Types of hooks
 
 
 ## Types of hooks
 


@@ -68,20 +148,21 @@ In roughly the order they are called.
 
 This allows for plugins to perform their own processing of command-line
 options and so add options to the ikiwiki command line. It's called during
 
 This allows for plugins to perform their own processing of command-line
 options and so add options to the ikiwiki command line. It's called during

-command line processing, with @ARGV full of any options that ikiwiki was
+command line processing, with `@ARGV` full of any options that ikiwiki was

 not able to process on its own. The function should process any options it
 not able to process on its own. The function should process any options it

-can, removing them from @ARGV, and probably recording the configuration
-settings in %config. It should take care not to abort if it sees
+can, removing them from `@ARGV`, and probably recording the configuration
+settings in `%config`. It should take care not to abort if it sees

 an option it cannot process, and should just skip over those options and
 an option it cannot process, and should just skip over those options and

-leave them in @ARGV.
+leave them in `@ARGV`.

 
 ### checkconfig
 
        hook(type => "checkconfig", id => "foo", call => \&checkconfig);
 
 This is useful if the plugin needs to check for or modify ikiwiki's
 
 ### checkconfig
 
        hook(type => "checkconfig", id => "foo", call => \&checkconfig);
 
 This is useful if the plugin needs to check for or modify ikiwiki's

-configuration. It's called early in the startup process. The
-function is passed no values. It's ok for the function to call
+configuration. It's called early in the startup process. `%config`
+is populated at this point, but other state has not yet been loaded.
+The function is passed no values. It's ok for the function to call

 `error()` if something isn't configured right.
 
 ### refresh
 `error()` if something isn't configured right.
 
 ### refresh


@@ -96,10 +177,15 @@ function is passed no values.
 
        hook(type => "needsbuild", id => "foo", call => \&needsbuild);
 
 
        hook(type => "needsbuild", id => "foo", call => \&needsbuild);
 

-This allows a plugin to manipulate the list of files that need to be
-built when the wiki is refreshed. The function is passed a reference to an
-array of pages that will be rebuilt, and can modify the array, either
-adding or removing files from it.
+This allows a plugin to observe or even manipulate the list of files that
+need to be built when the wiki is refreshed. 
+
+As its first parameter, the function is passed a reference to an array of
+files that will be built. It should return an array reference that is a
+modified version of its input. It can add or remove files from it.
+
+The second parameter passed to the function is a reference to an array of
+files that have been deleted.

 
 ### scan
 
 
 ### scan
 


@@ -107,8 +193,8 @@ adding or removing files from it.
 
 This hook is called early in the process of building the wiki, and is used
 as a first pass scan of the page, to collect metadata about the page. It's
 
 This hook is called early in the process of building the wiki, and is used
 as a first pass scan of the page, to collect metadata about the page. It's

-mostly used to scan the page for WikiLinks, and add them to `%links`.
-Present in IkiWiki 2.40 and later.
+mostly used to scan the page for [[WikiLinks|ikiwiki/WikiLink]], and add
+them to `%links`. Present in IkiWiki 2.40 and later.

 
 The function is passed named parameters "page" and "content". Its return
 value is ignored.
 
 The function is passed named parameters "page" and "content". Its return
 value is ignored.


@@ -117,8 +203,8 @@ value is ignored.
 
        hook(type => "filter", id => "foo", call => \&filter);
 
 
        hook(type => "filter", id => "foo", call => \&filter);
 

-Runs on the raw source of a page, before anything else touches it, and can
-make arbitrary changes. The function is passed named parameters "page",
+Runs on the full raw source of a page, before anything else touches it, and
+can make arbitrary changes. The function is passed named parameters "page",

 "destpage", and "content". It should return the filtered content.
 
 ### preprocess
 "destpage", and "content". It should return the filtered content.
 
 ### preprocess


@@ -151,11 +237,11 @@ parameter is set to a true value if the page is being previewed.
 If `hook` is passed an optional "scan" parameter, set to a true value, this
 makes the hook be called during the preliminary scan that ikiwiki makes of
 updated pages, before begining to render pages. This should be done if the
 If `hook` is passed an optional "scan" parameter, set to a true value, this
 makes the hook be called during the preliminary scan that ikiwiki makes of
 updated pages, before begining to render pages. This should be done if the

-hook modifies data in `%links`. Note that doing so will make the hook be
-run twice per page build, so avoid doing it for expensive hooks. (As an
-optimisation, if your preprocessor hook is called in a void context, you
-can assume it's being run in scan mode, and avoid doing expensive things at
-that point.)
+hook modifies data in `%links` (typically by calling `add_link`). Note that
+doing so will make the hook be run twice per page build, so avoid doing it
+for expensive hooks. (As an optimisation, if your preprocessor hook is
+called in a void context, you can assume it's being run in scan mode, and
+avoid doing expensive things at that point.)

 
 Note that if the [[htmlscrubber]] is enabled, html in
 preprocessor [[ikiwiki/directive]] output is sanitised, which may limit what
 
 Note that if the [[htmlscrubber]] is enabled, html in
 preprocessor [[ikiwiki/directive]] output is sanitised, which may limit what


@@ -168,13 +254,14 @@ htmlize the page) along with the rest of the page.
 
        hook(type => "linkify", id => "foo", call => \&linkify);
 
 
        hook(type => "linkify", id => "foo", call => \&linkify);
 

-This hook is called to convert [[WikiLinks|WikiLink]] on the page into html
+This hook is called to convert [[WikiLinks|ikiwiki/WikiLink]] on the page into html

 links. The function is passed named parameters "page", "destpage", and
 "content". It should return the linkified content.  Present in IkiWiki 2.40
 and later.
 
 Plugins that implement linkify must also implement a scan hook, that scans
 links. The function is passed named parameters "page", "destpage", and
 "content". It should return the linkified content.  Present in IkiWiki 2.40
 and later.
 
 Plugins that implement linkify must also implement a scan hook, that scans

-for the links on the page and adds them to `%links`.
+for the links on the page and adds them to `%links` (typically by calling
+`add_link`).

 
 ### htmlize
 
 
 ### htmlize
 


@@ -189,14 +276,33 @@ The function is passed named parameters: "page" and "content" and should
 return the htmlized content.
 
 If `hook` is passed an optional "keepextension" parameter, set to a true
 return the htmlized content.
 
 If `hook` is passed an optional "keepextension" parameter, set to a true

-value, then this extension will not be stripped from the source filename when
+value, then the extension will not be stripped from the source filename when

 generating the page.
 
 generating the page.
 

+If `hook` is passed an optional "noextension" parameter, set to a true
+value, then the id parameter specifies not a filename extension, but
+a whole filename that can be htmlized. This is useful for files
+like `Makefile` that have no extension.
+
+If `hook` is passed an optional "longname" parameter, this value is used
+when prompting a user to choose a page type on the edit page form.
+
+### indexhtml
+
+       hook(type => "indexhtml", id => "foo", call => \&indexhtml);
+
+This hook is called once the page has been converted to html (but before
+the generated html is put in a template). The most common use is to
+update search indexes. Added in ikiwiki 2.54.
+
+The function is passed named parameters "page", "destpage", and "content".
+Its return value is ignored.
+

 ### pagetemplate
 
        hook(type => "pagetemplate", id => "foo", call => \&pagetemplate);
 
 ### pagetemplate
 
        hook(type => "pagetemplate", id => "foo", call => \&pagetemplate);
 

-[[Templates|wikitemplates]] are filled out for many different things in
+[[Templates]] are filled out for many different things in

 ikiwiki, like generating a page, or part of a blog page, or an rss feed, or
 a cgi. This hook allows modifying the variables available on those
 templates. The function is passed named parameters. The "page" and
 ikiwiki, like generating a page, or part of a blog page, or an rss feed, or
 a cgi. This hook allows modifying the variables available on those
 templates. The function is passed named parameters. The "page" and


@@ -212,11 +318,20 @@ a new custom parameter to the template.
 
        hook(type => "templatefile", id => "foo", call => \&templatefile);
 
 
        hook(type => "templatefile", id => "foo", call => \&templatefile);
 

-This hook allows plugins to change the [[template|wikitemplates]] that is
+This hook allows plugins to change the [[template|templates]] that is

 used for a page in the wiki. The hook is passed a "page" parameter, and
 used for a page in the wiki. The hook is passed a "page" parameter, and

-should return the name of the template file to use, or undef if it doesn't
-want to change the default ("page.tmpl"). Template files are looked for in
-/usr/share/ikiwiki/templates by default.
+should return the name of the template file to use (relative to the
+template directory), or undef if it doesn't want to change the default
+("page.tmpl").
+
+### pageactions
+
+       hook(type => "pageactions", id => "foo", call => \&pageactions);
+
+This hook allows plugins to add arbitrary actions to the action bar on a
+page (next to Edit, RecentChanges, etc). The hook is passed a "page"
+parameter, and can return a list of html fragments to add to the action
+bar.

 
 ### sanitize
 
 
 ### sanitize
 


@@ -228,17 +343,6 @@ modify the body of a page after it has been fully converted to html.
 The function is passed named parameters: "page", "destpage", and "content",
 and should return the sanitized content.
 
 The function is passed named parameters: "page", "destpage", and "content",
 and should return the sanitized content.
 

-### postscan
-
-       hook(type => "postscan", id => "foo", call => \&postscan);
-
-This hook is called once the full page body is available (but before the
-format hook). The most common use is to update search indexes. Added in
-ikiwiki 2.54.
-
-The function is passed named parameters "page" and "content". Its return
-value is ignored.
-

 ### format
 
        hook(type => "format", id => "foo", call => \&format);
 ### format
 
        hook(type => "format", id => "foo", call => \&format);


@@ -252,6 +356,22 @@ when the page is being previewed.)
 The function is passed named parameters: "page" and "content", and 
 should return the formatted content.
 
 The function is passed named parameters: "page" and "content", and 
 should return the formatted content.
 

+### build_affected
+
+       hook(type => "build_affected", id => "foo", call => \&build_affected);
+
+This hook is called after the directly changed pages have been built,
+and can cause extra pages to be built. If links and backlinks were provided
+by a plugin, this would be where that plugin would rebuild pages whose
+backlinks have changed, for instance. The [[trail]] plugin uses this hook
+to rebuild pages whose next or previous page has changed.
+
+The function should currently ignore its parameters. It returns a list with
+an even number of items (a hash in list context), where the first item of
+each pair is a page name to be rebuilt (if it was not already rebuilt), and
+the second is a log message resembling
+`building plugins/write because the phase of the moon has changed`.
+

 ### delete
 
        hook(type => "delete", id => "foo", call => \&delete);
 ### delete
 
        hook(type => "delete", id => "foo", call => \&delete);


@@ -303,7 +423,7 @@ can check if the session object has a "name" parameter set.
 
 ### canedit
 
 
 ### canedit
 

-       hook(type => "canedit", id => "foo", call => \&pagelocked);
+       hook(type => "canedit", id => "foo", call => \&canedit);

 
 This hook can be used to implement arbitrary access methods to control when
 a page can be edited using the web interface (commits from revision control
 
 This hook can be used to implement arbitrary access methods to control when
 a page can be edited using the web interface (commits from revision control


@@ -321,6 +441,47 @@ This hook should avoid directly redirecting the user to a signin page,
 since it's sometimes used to test to see which pages in a set of pages a
 user can edit.
 
 since it's sometimes used to test to see which pages in a set of pages a
 user can edit.
 

+### canremove
+
+       hook(type => "canremove", id => "foo", call => \&canremove);
+
+This hook can be used to implement arbitrary access methods to control
+when a page can be removed using the web interface (commits from
+revision control bypass it). It works exactly like the `canedit` hook,
+but is passed the named parameters `cgi` (a CGI object), `session`
+(a session object) and `page` (the page subject to deletion).
+
+### canrename
+
+       hook(type => "canrename", id => "foo", call => \&canrename);
+
+This hook can be used to implement arbitrary access methods to control when
+a page can be renamed using the web interface (commits from revision control
+bypass it). It works exactly like the `canedit` hook,
+but is passed the named parameters `cgi` (a CGI object), `session` (a
+session object), `src`, `srcfile`, `dest` and `destfile`.
+
+### checkcontent
+       
+       hook(type => "checkcontent", id => "foo", call => \&checkcontent);
+
+This hook is called to check the content a user has entered on a page,
+before it is saved, and decide if it should be allowed.
+
+It is passed named parameters: `content`, `page`, `cgi`, and `session`. If
+the content the user has entered is a comment, it may also be passed some
+additional parameters: `author`, `url`, and `subject`. The `subject`
+parameter may also be filled with the user's comment about the change.
+
+Note: When the user edits an existing wiki page, this hook is also
+passed a `diff` named parameter, which will include only the lines
+that they added to the page, or modified.
+
+The hook should return `undef` on success. If the content is disallowed, it
+should return a message stating what the problem is, or a function
+that can be run to perform whatever action is necessary to allow the user
+to post the content.
+

 ### editcontent
 
        hook(type => "editcontent", id => "foo", call => \&editcontent);
 ### editcontent
 
        hook(type => "editcontent", id => "foo", call => \&editcontent);


@@ -365,9 +526,28 @@ they're saved, etc.
        hook(type => "renamepage", id => "foo", call => \&renamepage);
 
 This hook is called by the [[plugins/rename]] plugin when it renames
        hook(type => "renamepage", id => "foo", call => \&renamepage);
 
 This hook is called by the [[plugins/rename]] plugin when it renames

-something. The hook is passed named parameters: `page`, `oldpage`,
-`newpage`, and `content`, and should try to modify the content to reflect
-the name change. For example, by converting links to point to the new page.
+something, once per page linking to the renamed page's old location.
+The hook is passed named parameters: `page`, `oldpage`, `newpage`, and
+`content`, and should try to modify the content of `page` to reflect
+the name change. For example, by converting links to point to the
+new page.
+
+### rename
+
+       hook(type => "rename", id => "foo", call => \&rename);
+
+When a page or set of pages is renamed, the referenced function is
+called for every page, and is passed named parameters:
+
+* `torename`: a reference to a hash with keys: `src`, `srcfile`,
+  `dest`, `destfile`, `required`.
+* `cgi`: a CGI object
+* `session`: a session object.
+
+Such a hook function returns any additional rename hashes it wants to
+add. This hook is applied recursively to returned additional rename
+hashes, so that it handles the case where two plugins use the hook:
+plugin A would see when plugin B adds a new file to be renamed.

 
 ### getsetup
 
 
 ### getsetup
 


@@ -386,7 +566,13 @@ The data returned is a list of `%config` options, followed by a hash
 describing the option. There can also be an item named "plugin", which
 describes the plugin as a whole. For example:
 
 describing the option. There can also be an item named "plugin", which
 describes the plugin as a whole. For example:
 

-                return
+               return
+                       plugin => {
+                               description => "description of this plugin",
+                               safe => 1,
+                               rebuild => 1,
+                               section => "misc",
+                       },

                        option_foo => {
                                type => "boolean",
                                description => "enable foo?",
                        option_foo => {
                                type => "boolean",
                                description => "enable foo?",


@@ -401,11 +587,6 @@ describes the plugin as a whole. For example:
                                safe => 1,
                                rebuild => 0,
                        },
                                safe => 1,
                                rebuild => 0,
                        },

-                       plugin => {
-                               description => "description of this plugin",
-                               safe => 1,
-                               rebuild => 1,
-                       },

 
 * `type` can be "boolean", "string", "integer", "pagespec",
   or "internal" (used for values that are not user-visible). The type is
 
 * `type` can be "boolean", "string", "integer", "pagespec",
   or "internal" (used for values that are not user-visible). The type is


@@ -414,7 +595,8 @@ describes the plugin as a whole. For example:
 * `example` can be set to an example value.
 * `description` is a short description of the option.
 * `link` is a link to further information about the option. This can either
 * `example` can be set to an example value.
 * `description` is a short description of the option.
 * `link` is a link to further information about the option. This can either

-  be a wikilink, or an url.
+  be a [[ikiwiki/WikiLink]], or an url.
+* `htmldescription` is displayed instead of the description by websetup.

 * `advanced` can be set to true if the option is more suitable for advanced
   users.
 * `safe` should be false if the option should not be displayed in unsafe
 * `advanced` can be set to true if the option is more suitable for advanced
   users.
 * `safe` should be false if the option should not be displayed in unsafe


@@ -426,29 +608,38 @@ describes the plugin as a whole. For example:
   the plugin) will require a wiki rebuild, false if no rebuild is needed,
   and undef if a rebuild could be needed in some circumstances, but is not
   strictly required.
   the plugin) will require a wiki rebuild, false if no rebuild is needed,
   and undef if a rebuild could be needed in some circumstances, but is not
   strictly required.

+* `section` can optionally specify which section in the config file
+  the plugin fits in. The convention is to name the sections the
+  same as the tags used for [[plugins|plugin]] on this wiki.

 
 

-## Plugin interface
+### genwrapper

 
 

-To import the ikiwiki plugin interface:
+       hook(type => "genwrapper", id => "foo", call => \&genwrapper);

 
 

-       use IkiWiki '2.00';
+This hook is used to inject C code (which it returns) into the `main`
+function of the ikiwiki wrapper when it is being generated. 

 
 

-This will import several variables and functions into your plugin's
-namespace. These variables and functions are the ones most plugins need,
-and a special effort will be made to avoid changing them in incompatible
-ways, and to document any changes that have to be made in the future.
+The code runs before anything else -- in particular it runs before
+the suid wrapper has sanitized its environment.

 
 

-Note that IkiWiki also provides other variables and functions that are not
-exported by default. No guarantee is made about these in the future, so if
-it's not exported, the wise choice is to not use it.
+### disable
+
+       hook(type => "disable", id => "foo", call => \&disable);
+
+This hook is only run when a previously enabled plugin gets disabled
+during ikiwiki setup. Plugins can use this to perform cleanups.
+
+## Exported variables

 
 

-### %config
+Several variables are exported to your plugin when you `use IkiWiki;`
+
+### `%config`

 
 A plugin can access the wiki's configuration via the `%config`
 hash. The best way to understand the contents of the hash is to look at
 your ikiwiki setup file, which sets the hash content to configure the wiki.
 
 
 A plugin can access the wiki's configuration via the `%config`
 hash. The best way to understand the contents of the hash is to look at
 your ikiwiki setup file, which sets the hash content to configure the wiki.
 

-### %pagestate
+### `%pagestate`

 
 The `%pagestate` hash can be used by plugins to save state that they will need
 next time ikiwiki is run. The hash holds per-page state, so to set a value,
 
 The `%pagestate` hash can be used by plugins to save state that they will need
 next time ikiwiki is run. The hash holds per-page state, so to set a value,


@@ -466,7 +657,7 @@ When pages are deleted, ikiwiki automatically deletes their pagestate too.
 Note that page state does not persist across wiki rebuilds, only across
 wiki updates.
 
 Note that page state does not persist across wiki rebuilds, only across
 wiki updates.
 

-### %wikistate
+### `%wikistate`

 
 The `%wikistate` hash can be used by a plugin to store persistant state
 that is not bound to any one page. To set a value, use
 
 The `%wikistate` hash can be used by a plugin to store persistant state
 that is not bound to any one page. To set a value, use


@@ -475,23 +666,53 @@ serialize, `$key` is any string you like, and `$id` must be the same as the
 "id" parameter passed to `hook()` when registering the plugin, so that the
 state can be dropped if the plugin is no longer used.
 
 "id" parameter passed to `hook()` when registering the plugin, so that the
 state can be dropped if the plugin is no longer used.
 

-### Other variables
+### `%links`
+
+The `%links` hash can be used to look up the names of each page that
+a page links to. The name of the page is the key; the value is an array
+reference. Do not modify this hash directly; call `add_link()`.
+
+       $links{"foo"} = ["bar", "baz"];
+
+### `%typedlinks`
+
+The `%typedlinks` hash records links of specific types. Do not modify this
+hash directly; call `add_link()`. The keys are page names, and the values
+are hash references. In each page's hash reference, the keys are link types
+defined by plugins, and the values are hash references with link targets
+as keys, and 1 as a dummy value, something like this:

 
 

-If your plugin needs to access data about other pages in the wiki. It can
-use the following hashes, using a page name as the key:
+       $typedlinks{"foo"} = {
+               tag => { short_word => 1, metasyntactic_variable => 1 },
+               next_page => { bar => 1 },
+       };

 
 

-* `%links` lists the names of each page that a page links to, in an array
-  reference.
-* `%destsources` contains the name of the source file used to create each
-  destination file.
-* `%pagesources` contains the name of the source file for each page.
+Ordinary [[WikiLinks|ikiwiki/WikiLink]] appear in `%links`, but not in
+`%typedlinks`.

 
 

-Also, the %IkiWiki::version variable contains the version number for the
-ikiwiki program.
+### `%pagesources`

 
 

-### Library functions
+The `%pagesources` has can be used to look up the source filename
+of a page. So the key is the page name, and the value is the source
+filename. Do not modify this hash.

 
 

-#### `hook(@)`
+       $pagesources{"foo"} = "foo.mdwn";
+
+### `%destsources`
+
+The `%destsources` hash records the name of the source file used to
+create each destination file. The key is the output filename (ie,
+"foo/index.html"), and the value is the source filename that it was built
+from (eg, "foo.mdwn"). Note that a single source file may create multiple
+destination files. Do not modify this hash directly; call `will_render()`.
+       
+       $destsources{"foo/index.html"} = "foo.mdwn";
+
+## Library functions
+
+Several functions are exported to your plugin when you `use IkiWiki;`
+
+### `hook(@)`

 
 Hook into ikiwiki's processing. See the discussion of hooks above.
 
 
 Hook into ikiwiki's processing. See the discussion of hooks above.
 


@@ -500,12 +721,12 @@ named `no_override` is supported, If it's set to a true value, then this hook
 will not override any existing hook with the same id. This is useful if
 the id can be controled by the user.
 
 will not override any existing hook with the same id. This is useful if
 the id can be controled by the user.
 

-#### `debug($)`
+### `debug($)`

 
 Logs a debugging message. These are supressed unless verbose mode is turned
 on.
 
 
 Logs a debugging message. These are supressed unless verbose mode is turned
 on.
 

-#### `error($;$)`
+### `error($;$)`

 
 Aborts with an error message. If the second parameter is passed, it is a
 function that is called after the error message is printed, to do any final
 
 Aborts with an error message. If the second parameter is passed, it is a
 function that is called after the error message is printed, to do any final


@@ -519,13 +740,34 @@ In other hooks, error() is a fatal error, so use with care. Try to avoid
 dying on bad input when building a page, as that will halt
 the entire wiki build and make the wiki unusable.
 
 dying on bad input when building a page, as that will halt
 the entire wiki build and make the wiki unusable.
 

-#### `template($;@)`
+### `template($;@)`
+
+Creates and returns a [[!cpan HTML::Template]] object. (In a list context,
+returns the parameters needed to construct the obhect.) 

 
 

-Creates and returns a [[!cpan HTML::Template]] object. The first parameter
-is the name of the file in the template directory. The optional remaining
+The first parameter is the name of the template file. The optional remaining

 parameters are passed to `HTML::Template->new`.
 
 parameters are passed to `HTML::Template->new`.
 

-#### `htmlpage($)`
+Normally, the template file is first looked for in the templates/ subdirectory
+of the srcdir. Failing that, it is looked for in the templatedir.
+
+Wiki pages can be used as templates. This should be done only for templates
+which it is safe to let wiki users edit. Enable it by passing a filename
+with no ".tmpl" extension. Template pages are normally looked for in
+the templates/ directory. If the page name starts with "/", a page
+elsewhere in the wiki can be used.
+
+If the template is not found, or contains a syntax error, an error is thrown.
+
+### `template_depends($$;@)`
+
+Use this instead of `template()` if the content of a template is being
+included into a page. This causes the page to depend on the template,
+so it will be updated if the template is modified.
+
+Like `template()`, except the second parameter is the page.
+
+### `htmlpage($)`

 
 Passed a page name, returns the base name that will be used for a the html
 page created from it. (Ie, it appends ".html".)
 
 Passed a page name, returns the base name that will be used for a the html
 page created from it. (Ie, it appends ".html".)


@@ -533,21 +775,79 @@ page created from it. (Ie, it appends ".html".)
 Use this when constructing the filename of a html file. Use `urlto` when
 generating a link to a page.
 
 Use this when constructing the filename of a html file. Use `urlto` when
 generating a link to a page.
 

-#### `add_depends($$)`
+### `pagespec_match_list($$;@)`
+
+Passed a page name, and [[ikiwiki/PageSpec]], returns a list of pages
+in the wiki that match the [[ikiwiki/PageSpec]]. 
+
+The page will automatically be made to depend on the specified
+[[ikiwiki/PageSpec]], so `add_depends` does not need to be called. This
+is often significantly more efficient than calling `add_depends` and
+`pagespec_match` in a loop. You should use this anytime a plugin
+needs to match a set of pages and do something based on that list.
+
+Unlike pagespec_match, this may throw an error if there is an error in
+the pagespec.
+
+Additional named parameters can be specified:
+
+* `deptype` optionally specifies the type of dependency to add. Use the
+  `deptype` function to generate a dependency type.
+* `filter` is a reference to a function, that is called and passed a page,
+  and returns true if the page should be filtered out of the list.
+* `sort` specifies a sort order for the list. See
+  [[ikiwiki/PageSpec/sorting]] for the avilable sort methods. Note that
+  if a sort method is specified that depends on the
+  page content (such as 'meta(foo)'), the deptype needs to be set to
+  a content dependency.
+* `reverse` if true, sorts in reverse.
+* `num` if nonzero, specifies the maximum number of matching pages that
+  will be returned.
+* `list` makes it only match amoung the specified list of pages.
+  Default is to match amoung all pages in the wiki.
+
+Any other named parameters are passed on to `pagespec_match`, to further
+limit the match.
+
+### `add_depends($$;$)`

 
 Makes the specified page depend on the specified [[ikiwiki/PageSpec]].
 
 
 Makes the specified page depend on the specified [[ikiwiki/PageSpec]].
 

-#### `pagespec_match($$;@)`
+By default, dependencies are full content dependencies, meaning that the
+page will be updated whenever anything matching the PageSpec is modified.
+This can be overridden by passing a `deptype` value as the third parameter.

 
 

-Passed a page name, and [[ikiwiki/PageSpec]], returns true if the
+### `pagespec_match($$;@)`
+
+Passed a page name, and [[ikiwiki/PageSpec]], returns a true value if the

 [[ikiwiki/PageSpec]] matches the page.
 
 [[ikiwiki/PageSpec]] matches the page.
 

+Note that the return value is overloaded. If stringified, it will be a
+message indicating why the PageSpec succeeded, or failed, to match the
+page.
+

 Additional named parameters can be passed, to further limit the match.
 The most often used is "location", which specifies the location the
 PageSpec should match against. If not passed, relative PageSpecs will match
 relative to the top of the wiki.
 
 Additional named parameters can be passed, to further limit the match.
 The most often used is "location", which specifies the location the
 PageSpec should match against. If not passed, relative PageSpecs will match
 relative to the top of the wiki.
 

-#### `bestlink($$)`
+### `deptype(@)`
+
+Use this function to generate ikiwiki's internal representation of a
+dependency type from one or more of these keywords:
+
+* `content` is the default. Any change to the content
+  of a page triggers the dependency.
+* `presence` is only triggered by a change to the presence
+  of a page.
+* `links` is only triggered by a change to the links of a page.
+  This includes when a link is added, removed, or changes what
+  it points to due to other changes. It does not include the
+  addition or removal of a duplicate link.
+
+If multiple types are specified, they are combined.
+
+### `bestlink($$)`

 
 Given a page and the text of a link on the page, determine which
 existing page that link best points to. Prefers pages under a
 
 Given a page and the text of a link on the page, determine which
 existing page that link best points to. Prefers pages under a


@@ -555,11 +855,11 @@ subdirectory with the same name as the source page, failing that
 goes down the directory tree to the base looking for matching
 pages, as described in [[ikiwiki/SubPage/LinkingRules]].
 
 goes down the directory tree to the base looking for matching
 pages, as described in [[ikiwiki/SubPage/LinkingRules]].
 

-#### `htmllink($$$;@)`
+### `htmllink($$$;@)`

 
 Many plugins need to generate html links and add them to a page. This is
 done by using the `htmllink` function. The usual way to call
 
 Many plugins need to generate html links and add them to a page. This is
 done by using the `htmllink` function. The usual way to call

-`htmlllink` is:
+`htmllink` is:

 
        htmllink($page, $page, $link)
 
 
        htmllink($page, $page, $link)
 


@@ -581,8 +881,9 @@ control some options. These are:
 * anchor - set to make the link include an anchor
 * rel - set to add a rel attribute to the link
 * class - set to add a css class to the link
 * anchor - set to make the link include an anchor
 * rel - set to add a rel attribute to the link
 * class - set to add a css class to the link

+* title - set to add a title attribute to the link

 
 

-#### `readfile($;$)`
+### `readfile($;$)`

 
 Given a filename, reads and returns the entire file.
 
 
 Given a filename, reads and returns the entire file.
 


@@ -591,7 +892,7 @@ in binary mode.
 
 A failure to read the file will result in it dying with an error.
 
 
 A failure to read the file will result in it dying with an error.
 

-#### `writefile($$$;$$)`
+### `writefile($$$;$$)`

 
 Given a filename, a directory to put it in, and the file's content,
 writes a file. 
 
 Given a filename, a directory to put it in, and the file's content,
 writes a file. 


@@ -609,7 +910,17 @@ A failure to write the file will result in it dying with an error.
 
 If the destination directory doesn't exist, it will first be created.
 
 
 If the destination directory doesn't exist, it will first be created.
 

-#### `will_render($$)`
+The filename and directory are separate parameters because of
+some security checks done to avoid symlink attacks. Before writing a file,
+it checks to make sure there's not a symlink with its name, to avoid
+following the symlink. If the filename parameter includes a subdirectory
+to put the file in, it also checks if that subdirectory is a symlink, etc.
+The directory parameter, however, is not checked for symlinks. So,
+generally the directory parameter is a trusted toplevel directory like
+the srcdir or destdir, and any subdirectories of this are included in the
+filename parameter.
+
+### `will_render($$)`

 
 Given a page name and a destination file name (not including the base
 destination directory), register that the page will result in that file
 
 Given a page name and a destination file name (not including the base
 destination directory), register that the page will result in that file


@@ -625,34 +936,34 @@ Ikiwiki uses this information to automatically clean up rendered files when
 the page that rendered them goes away or is changed to no longer render
 them. will_render also does a few important security checks.
 
 the page that rendered them goes away or is changed to no longer render
 them. will_render also does a few important security checks.
 

-#### `pagetype($)`
+### `pagetype($)`

 
 Given the name of a source file, returns the type of page it is, if it's
 a type that ikiwiki knowns how to htmlize. Otherwise, returns undef.
 
 
 Given the name of a source file, returns the type of page it is, if it's
 a type that ikiwiki knowns how to htmlize. Otherwise, returns undef.
 

-#### `pagename($)`
+### `pagename($)`

 
 Given the name of a source file, returns the name of the wiki page
 that corresponds to that file.
 
 
 Given the name of a source file, returns the name of the wiki page
 that corresponds to that file.
 

-#### `pagetitle($)`
+### `pagetitle($)`

 
 Give the name of a wiki page, returns a version suitable to be displayed as
 the page's title. This is accomplished by de-escaping escaped characters in
 the page name. "_" is replaced with a space, and '__NN__' is replaced by 
 the UTF character with code NN.
 
 
 Give the name of a wiki page, returns a version suitable to be displayed as
 the page's title. This is accomplished by de-escaping escaped characters in
 the page name. "_" is replaced with a space, and '__NN__' is replaced by 
 the UTF character with code NN.
 

-#### `titlepage($)`
+### `titlepage($)`

 
 This performs the inverse of `pagetitle`, ie, it converts a page title into
 a wiki page name.
 
 
 This performs the inverse of `pagetitle`, ie, it converts a page title into
 a wiki page name.
 

-#### `linkpage($)`
+### `linkpage($)`

 
 This converts text that could have been entered by the user as a
 
 This converts text that could have been entered by the user as a

-[[WikiLink]] into a wiki page name.
+[[ikiwiki/WikiLink]] into a wiki page name.

 
 

-#### `srcfile($;$)`
+### `srcfile($;$)`

 
 Given the name of a source file in the wiki, searches for the file in
 the source directory and the underlay directories (most recently added
 
 Given the name of a source file in the wiki, searches for the file in
 the source directory and the underlay directories (most recently added


@@ -662,7 +973,7 @@ Normally srcfile will fail with an error message if the source file cannot
 be found. The second parameter can be set to a true value to make it return
 undef instead.
 
 be found. The second parameter can be set to a true value to make it return
 undef instead.
 

-#### `add_underlay($)`
+### `add_underlay($)`

 
 Adds a directory to the set of underlay directories that ikiwiki will
 search for files.
 
 Adds a directory to the set of underlay directories that ikiwiki will
 search for files.


@@ -670,37 +981,81 @@ search for files.
 If the directory name is not absolute, ikiwiki will assume it is in
 the parent directory of the configured underlaydir.
 
 If the directory name is not absolute, ikiwiki will assume it is in
 the parent directory of the configured underlaydir.
 

-#### `displaytime($;$)`
+### `displaytime($;$$)`

 
 Given a time, formats it for display.
 
 The optional second parameter is a strftime format to use to format the
 time.
 
 
 Given a time, formats it for display.
 
 The optional second parameter is a strftime format to use to format the
 time.
 

-#### `gettext`
+If the third parameter is true, this is the publication time of a page.
+(Ie, set the html5 pubdate attribute.)
+
+### `gettext`

 
 This is the standard gettext function, although slightly optimised.
 
 
 This is the standard gettext function, although slightly optimised.
 

-#### `urlto($$;$)`
+### `ngettext`
+
+This is the standard ngettext function, although slightly optimised.
+
+### `urlto($;$$)`

 
 Construct a relative url to the first parameter from the page named by the
 second. The first parameter can be either a page name, or some other
 destination file, as registered by `will_render`.
 
 
 Construct a relative url to the first parameter from the page named by the
 second. The first parameter can be either a page name, or some other
 destination file, as registered by `will_render`.
 

-If the third parameter is passed and is true, an absolute url will be
-constructed instead of the default relative url.
+Provide a second parameter whenever possible, since this leads to better
+behaviour for the [[plugins/po]] plugin and `file:///` URLs.
+
+If the second parameter is not specified (or `undef`), the URL will be
+valid from any page on the wiki, or from the CGI; if possible it'll
+be a path starting with `/`, but an absolute URL will be used if
+the wiki and the CGI are on different domains.

 
 

-#### `newpagefile($$)`
+If the third parameter is passed and is true, the url will be a fully
+absolute url. This is useful when generating an url to publish elsewhere.
+
+### `newpagefile($$)`

 
 This can be called when creating a new page, to determine what filename
 to save the page to. It's passed a page name, and its type, and returns
 the name of the file to create, relative to the srcdir.
 
 
 This can be called when creating a new page, to determine what filename
 to save the page to. It's passed a page name, and its type, and returns
 the name of the file to create, relative to the srcdir.
 

-#### `targetpage($$)`
+### `targetpage($$;$)`

 
 Passed a page and an extension, returns the filename that page will be
 rendered to.
 
 
 Passed a page and an extension, returns the filename that page will be
 rendered to.
 

+Optionally, a third parameter can be passed, to specify the preferred
+filename of the page. For example, `targetpage("foo", "rss", "feed")`
+will yield something like `foo/feed.rss`.
+
+### `add_link($$;$)`
+
+This adds a link to `%links`, ensuring that duplicate links are not
+added. Pass it the page that contains the link, and the link text.
+
+An optional third parameter sets the link type. If not specified,
+it is an ordinary [[ikiwiki/WikiLink]].
+
+### `add_autofile($$$)`
+
+Sometimes you may want to add a file to the `srcdir` as a result of content
+of other pages. For example, [[plugins/tag]] pages can be automatically
+created as needed. This function can be used to do that. 
+
+The three parameters are the filename to create (relative to the `srcdir`),
+the name of the plugin, and a callback function. The callback will be
+called if it is appropriate to automatically add the file, and should then
+take care of creating it, and doing anything else it needs to (such as
+checking it into revision control). Note that the callback may not always
+be called. For example, if an automatically added file is deleted by the
+user, ikiwiki will avoid re-adding it again.
+
+This function needs to be called during the scan hook, or earlier in the
+build process, in order to add the file early enough for it to be built.
+

 ## Miscellaneous
 
 ### Internal use pages
 ## Miscellaneous
 
 ### Internal use pages


@@ -711,7 +1066,7 @@ are collected together to form the RecentChanges page, for example.
 
 To make an internal use page, register a filename extension that starts
 with "_". Internal use pages cannot be edited with the web interface,
 
 To make an internal use page, register a filename extension that starts
 with "_". Internal use pages cannot be edited with the web interface,

-generally shouldn't contain wikilinks or preprocessor directives (use
+generally shouldn't contain [[WikiLinks|ikiwiki/WikiLink]] or preprocessor directives (use

 either on them with extreme caution), and are not matched by regular
 PageSpecs glob patterns, but instead only by a special `internal()`
 [[ikiwiki/PageSpec]].
 either on them with extreme caution), and are not matched by regular
 PageSpecs glob patterns, but instead only by a special `internal()`
 [[ikiwiki/PageSpec]].


@@ -738,18 +1093,22 @@ token, that will be passed into `rcs_commit` when committing. For example,
 it might return the current revision ID of the file, and use that
 information later when merging changes.
 
 it might return the current revision ID of the file, and use that
 information later when merging changes.
 

-#### `rcs_commit($$$;$$)`
+#### `rcs_commit(@)`
+
+Passed named parameters: `file`, `message`, `token` (from `rcs_prepedit`),
+and `session` (optional).

 
 

-Passed a file, message, token (from `rcs_prepedit`), user, and ip address.

 Should try to commit the file. Returns `undef` on *success* and a version
 of the page with the rcs's conflict markers on failure.
 
 Should try to commit the file. Returns `undef` on *success* and a version
 of the page with the rcs's conflict markers on failure.
 

-#### `rcs_commit_staged($$$)`
+#### `rcs_commit_staged(@)`

 
 

-Passed a message, user, and ip address. Should commit all staged changes.
-Returns undef on success, and an error message on failure.
+Passed named parameters: `message`, and `session` (optional).

 
 

-Changes can be staged by calls to `rcs_add, `rcs_remove`, and
+Should commit all staged changes. Returns undef on success, and an
+error message on failure.
+
+Changes can be staged by calls to `rcs_add`, `rcs_remove`, and

 `rcs_rename`.
 
 #### `rcs_add($)`
 `rcs_rename`.
 
 #### `rcs_add($)`


@@ -767,9 +1126,7 @@ to version control; the subdir can be added if so.
 Remove a file. The filename is relative to the root of the srcdir.
 
 Note that this should not commit the removal, it should only prepare for it
 Remove a file. The filename is relative to the root of the srcdir.
 
 Note that this should not commit the removal, it should only prepare for it

-to be committed when `rcs_commit` (or `rcs_commit_staged`) is called. Note
-that the new file may be in a new subdir that is not yet in version
-control; the subdir can be added if so.
+to be committed when `rcs_commit` (or `rcs_commit_staged`) is called.

 
 #### `rcs_rename($$)`
 
 
 #### `rcs_rename($$)`
 


@@ -790,7 +1147,9 @@ The data structure returned for each change is:
 
        {
                rev => # the RCSs id for this commit
 
        {
                rev => # the RCSs id for this commit

-               user => # name of user who made the change,
+               user => # user who made the change (may be an openid),
+               nickname => # short name for user (optional; not an openid),
+               

                committype => # either "web" or the name of the rcs,
                when => # time when the change was made,
                message => [
                committype => # either "web" or the name of the rcs,
                when => # time when the change was made,
                message => [


@@ -807,19 +1166,30 @@ The data structure returned for each change is:
                ],
        }
 
                ],
        }
 

-#### `rcs_diff($)`
+#### `rcs_diff($;$)`
+
+The first parameter is the rev from `rcs_recentchanges`.
+The optional second parameter is how many lines to return (default: all).

 
 

-The parameter is the rev from `rcs_recentchanges`.

 Should return a list of lines of the diff (including \n) in list
 Should return a list of lines of the diff (including \n) in list

-context, and the whole diff in scalar context.
+context, and a string containing the whole diff in scalar context.

 
 #### `rcs_getctime($)`
 
 This is used to get the page creation time for a file from the RCS, by looking
 it up in the history.
 
 
 #### `rcs_getctime($)`
 
 This is used to get the page creation time for a file from the RCS, by looking
 it up in the history.
 

+If the RCS cannot determine a ctime for the file, return 0.
+
+#### `rcs_getmtime($)`
+
+This is used to get the page modification time for a file from the RCS, by
+looking it up in the history.
+

 It's ok if this is not implemented, and throws an error.
 
 It's ok if this is not implemented, and throws an error.
 

+If the RCS cannot determine a mtime for the file, return 0.
+

 #### `rcs_receive()`
 
 This is called when ikiwiki is running as a pre-receive hook (or
 #### `rcs_receive()`
 
 This is called when ikiwiki is running as a pre-receive hook (or


@@ -829,9 +1199,9 @@ sense to implement for all RCSs.
 
 It should examine the incoming changes, and do any sanity 
 checks that are appropriate for the RCS to limit changes to safe file adds,
 
 It should examine the incoming changes, and do any sanity 
 checks that are appropriate for the RCS to limit changes to safe file adds,

-removes, and changes. If something bad is found, it should exit
-nonzero, to abort the push. Otherwise, it should return a list of
-files that were changed, in the form:
+removes, and changes. If something bad is found, it should die, to abort
+the push. Otherwise, it should return a list of files that were changed,
+in the form:

 
        {
                file => # name of file that was changed
 
        {
                file => # name of file that was changed


@@ -844,6 +1214,28 @@ files that were changed, in the form:
 The list will then be checked to make sure that each change is one that
 is allowed to be made via the web interface.
 
 The list will then be checked to make sure that each change is one that
 is allowed to be made via the web interface.
 

+#### `rcs_preprevert($)`
+
+This is called by the revert web interface. It is passed a RCS-specific
+change ID, and should determine what the effects would be of reverting
+that change, and return the same data structure as `rcs_receive`.
+
+Like `rcs_receive`, it should do whatever sanity checks are appropriate
+for the RCS to limit changes to safe changes, and die if a change would
+be unsafe to revert.
+
+#### `rcs_revert($)`
+
+This is called by the revert web interface. It is passed a named
+parameter rev that is the RCS-specific change ID to revert.
+
+It should try to revert the specified rev, and leave the reversion staged
+so `rcs_commit_staged` will complete it. It should return undef on _success_
+and an error message on failure.
+
+This hook and `rcs_preprevert` are optional, if not implemented, no revert
+web interface will be available.
+

 ### PageSpec plugins
 
 It's also possible to write plugins that add new functions to
 ### PageSpec plugins
 
 It's also possible to write plugins that add new functions to


@@ -851,9 +1243,39 @@ It's also possible to write plugins that add new functions to
 IkiWiki::PageSpec package, that is named `match_foo`, where "foo()" is
 how it will be accessed in a [[ikiwiki/PageSpec]]. The function will be passed
 two parameters: The name of the page being matched, and the thing to match
 IkiWiki::PageSpec package, that is named `match_foo`, where "foo()" is
 how it will be accessed in a [[ikiwiki/PageSpec]]. The function will be passed
 two parameters: The name of the page being matched, and the thing to match

-against. It may also be passed additional, named parameters. It should return
-a IkiWiki::SuccessReason object if the match succeeds, or an
-IkiWiki::FailReason object if the match fails.
+against. It may also be passed additional, named parameters.
+
+It should return a IkiWiki::SuccessReason object if the match succeeds, or
+an IkiWiki::FailReason object if the match fails. If the match cannot be
+attempted at all, for any page, it can instead return an
+IkiWiki::ErrorReason object explaining why.
+
+When constructing these objects, you should also include information about
+of any pages whose contents or other metadata influenced the result of the
+match. Do this by passing a list of pages, followed by `deptype` values.
+
+For example, "backlink(foo)" is influenced by the contents of page foo;
+"link(foo)" and "title(bar)" are influenced by the contents of any page
+they match; "created_before(foo)" is influenced by the metadata of foo;
+while "glob(*)" is not influenced by the contents of any page.
+
+### Sorting plugins
+
+Similarly, it's possible to write plugins that add new functions as
+[[ikiwiki/pagespec/sorting]] methods. To achieve this, add a function to
+the IkiWiki::SortSpec package named `cmp_foo`, which will be used when sorting
+by `foo` or `foo(...)` is requested.
+
+The names of pages to be compared are in the global variables `$a` and `$b`
+in the IkiWiki::SortSpec package. The function should return the same thing
+as Perl's `cmp` and `<=>` operators: negative if `$a` is less than `$b`,
+positive if `$a` is greater, or zero if they are considered equal. It may
+also raise an error using `error`, for instance if it needs a parameter but
+one isn't provided.
+
+The function will also be passed one or more parameters. The first is
+`undef` if invoked as `foo`, or the parameter `"bar"` if invoked as `foo(bar)`;
+it may also be passed additional, named parameters.

 
 ### Setup plugins
 
 
 ### Setup plugins
 


@@ -880,7 +1302,7 @@ or wrap one of the functions.
 For example, your plugin might want to override `displaytime`, to change
 the html markup used when displaying a date. Or it might want to override
 `IkiWiki::formattime`, to change how a date is formatted. Or perhaps you
 For example, your plugin might want to override `displaytime`, to change
 the html markup used when displaying a date. Or it might want to override
 `IkiWiki::formattime`, to change how a date is formatted. Or perhaps you

-want to override `bestlink` and change how ikiwiki deals with WikiLinks.
+want to override `bestlink` and change how ikiwiki deals with [[WikiLinks|ikiwiki/WikiLink]].

 
 By venturing into this territory, your plugin is becoming tightly tied to
 ikiwiki's internals. And it might break if those internals change. But
 
 By venturing into this territory, your plugin is becoming tightly tied to
 ikiwiki's internals. And it might break if those internals change. But