+
+
+>>> I've tweaked my patch in light of your above feedback: The plugin has been
+>>> renamed, and I now validate keys. I've also added documentation and tests
+>>> to the branch. I haven't read rubykat's code properly yet, and don't have
+>>> access at the time of writing (I'm on a beach in Greece ☺), but I expect it
+>>> would be possible to extend what I've got here to support defining the
+>>> aliases in a PageSpec, once the dependency stuff has been reasoned out
+>>> properly.
+>>>
+>>> I'd like to solve the issue of this not being web-configurable by
+>>> implementing support for more nested datatypes in [[plugins/websetup]]. —
+>>> [[Jon]]
+
+>>>> Well, it's a difficult problem. websetup builds a form using
+>>>> CGI::FormBuilder, which makes it easy to build the simple UI we have
+>>>> now, but sorta precludes anything more complicated. And anything with
+>>>> a nested datatype probably needs a customized UI for users to be able
+>>>> to deal with it. I don't think websetupability need be a deal-breaker
+>>>> for this patch. I personally like special pages like Kathryn is doing
+>>>> more than complex setup files. --[[Joey]]
+
+>>>>> I've ran out of time to keep working on this, so I'm just going to
+>>>>> submit it as a 'contrib' plugin and leave things at that for now.
+>>>>> — [[Jon]]
+
+---------------------------
+
+Based on the above, I have written an experimental plugin called "subset".
+It's in my "ikiplugins" repo on github, in the "experimental" branch.
+<https://github.com/rubykat/ikiplugins/blob/experimental/IkiWiki/Plugin/subset.pm>
+
+It takes Joey's suggestion of defining the subsets (aliases) as directives;
+I took the example of the [[plugins/shortcut]] plugin and designated a single special page as the one where the directives are defined,
+though unlike "shortcut" I haven't hardcoded the name of the page; it defaults to "subsets" but it can be re-defined in the config.
+
+I've also added a feature which one might call subset-caching; I had to override `pagespec_match_list` to do it, however.
+An extra parameter added to `pagespec_match_list` called `subset` which
+
+* limits the result to look *only* within the set of pages defined by the subset (uses the "list" option to pagespec_match_list to do this)
+* caches the result of the subset search so that the second time subset "foo" is used, it uses the stored result of the first search for "foo".
+
+This speeds things up if one is using a particular subset more than once, which one probably is if one bothered to define the subset in the first place.
+The speed increase is most dramatic when the site has a large number of pages and the number of pages in the subset is small.
+(this is similar to the "trail" concept I used in my [[plugins/contrib/report]] plugin, but not quite the same)
+
+Note that things like [[plugins/map]] can't make use of "subset" (yet) because they don't pass along all the parameters they're given.
+But [[plugins/contrib/report]] actually works without alteration because it does pass along all the parameters.
+
+Unfortunately I haven't figured out how to do the dependencies - I'd really appreciate help on that.
+
+--[[KathrynAndersen]]
+
+> > Cool! I like the caching idea. I'm not sure about the name. I don't like defining
+> > stuff in pages, but I appreciate this is a matter of taste, and would be happy with
+> > supporting both. — [[Jon]]
+
+>>> I've now gone and completely re-done "subset" so that it is less like an alias, but it a bit clearer and simpler:
+>>> instead of having a separate "match_" function for every alias, I simply have one function, "match_subset"
+>>> which takes the name of the subset. Thus a \[[!subset name="foo"...]] would be called `subset(foo)` rather than `foo()`.
+
+>>> There are a few reasons for this:<br/>
+>>> (a) it's more secure not to be evaluating code on the fly<br/>
+>>> (b) it's simpler<br/>
+>>> (c) (and this was my main reason) it makes it possible to do caching without having to have a separate "subset" argument.
+>>> I've done a bit of a hack for this: basically, the PageSpec is checked to see if the very start of the PageSpec is `subset(foo) and` or if the whole pagespec is just `subset(foo)` and if either of those is true, then it does the subset caching stuff.
+>>> The reason I check for "and" is that if it is "subset(foo) or something" then it would be an error to use the subset cache in that case.
+>>> The reason I just check the start of the PageSpec is because I don't want to have to do complex parsing of the PageSpec.
+
+>>> As for defining subsets in the config rather than on pages, I perfectly understand that desire, and I could probably add that in.
+
+>>> As for the name "subset"... well, it's even less like an alias now, and "alias" is already a reserved name. What other names would you suggest?
+
+>>>--[[KathrynAndersen]]
+
+>>>> Regarding my comments: I wasn't clear what you are/were intending to
+>>>> achieve with your modifications. I've aimed for a self-contained plugin
+>>>> which could be merged with ikiwiki proper. I think I initially took your
+>>>> developments as being an evolution of that with the same goal, which is
+>>>> why I commented on the (change of) name. However, I guess your work is
+>>>> more of a fork than a continuation, in which case you can call it
+>>>> whatever you like ☺ I like some of the enhancements you've made, but
+>>>> having the aliases/subsets/"things" work in any pagespec (inside map, or
+>>>> inline) is a deal-breaker for me. — [[Jon]]
+
+>>>>> I'm a bit confused by your statement "having the aliases/subsets/"things" work in any pagespec (inside map, or inline) is a deal-breaker for me".
+>>>>> Do you mean that you want them to work in any pagespec, or that you *don't* want them to work in any pagespec? -- [[KathrynAndersen]]
+
+>>>>>> I mean I would want them to work in any pagespec. — [[Jon]]
+
+----
+
+Hi, it's been 7 years since I last looked at this, and I'm surprised to find
+that I'd got it up to a merge-request state; I've dusted it off and done some
+clean up and testing, but it's working (albeit not via websetup). I've revamped
+the docs and rebased the branch. Can someone please consider merging ([[joey]]
+or [[smcv]]?) or otherwise feed back on this? Thanks! — [[Jon]] (2018-09-25)
+
+> To hide it from `websetup`, the `example` needs to be a hash reference
+> like `example => { images => "*.png or *.jpg or *.gif" }`, I think?
+> (Please try it on a websetup-enabled wiki, possibly by copying
+> `t/manual/git_revert` to `t/manual/websetup` and adapting it as required.)
+>
+> For a less magical variant, you could consider using `alias(images)`
+> instead of `images()` for the pagespec syntax that is enabled by the
+> example above. I'm not sure which way is better.
+>
+> If `safe_key` fails, you probably want to log a warning, or even fail
+> `checkconfig` with a fatal `error`?
+>
+> If `checkconfig` detects that the given pagespec function already
+> exists, for example `title` after loading the meta plugin, you probably
+> want to log a warning or fail? It seems you can detect this with
+> `defined ref *$subname{CODE}`.
+>
+> If you define a loop of mutually recursive aliases (or even an alias
+> that refers to itself), I think you'll get infinite recursion.
+> You can probably bypass that with a construct like:
+>
+> my $entered;
+> *{ $subname } = sub {
+> return IkiWiki::ErrorReason->new("Alias $key is defined recursively") if $entered;
+> $entered = 1;
+> my $result = IkiWiki::pagespec_match($path, $value);
+> $entered = 0;
+> return $result;
+> }
+>
+> (but don't take my word for it, a regression test would tell you whether
+> this works.)
+>
+> --[[smcv]]