T77903 isn't a duplicate of this task, it's more of a relatively easy fix until we get those long standing difficult core problems solved, which may not be before a very long time.

@Parent5446, this task is assigned to you. Do you want to work on it or propose it to the next GSoC/Outreachy round?

There is a partial patch from way back. See comments on gerrit.

(In reply to comment #63)

Question:

Is there a potential mentor willing to help potential students interested in
this project?

Yes me :)

Does this still hold true @Bawolff?

(In reply to comment #63)

Question:

Is there a potential mentor willing to help potential students interested in
this project?

Yes me :)

Does this still hold true @Bawolff?

Not really. Like if there was a student who really super wanted to do this idea and no other, maybe, but generally I'd rather not mentor this idea, this round.

This is a message posted to all tasks under "Re-check in September 2015" at Possible-Tech-Projects. Outreachy-Round-11 is around the corner. If you want to propose this task as a featured project idea, we need a clear plan with community support, and two mentors willing to support it.

As previously mentioned, this task is moved to 'Recheck in February 2016' as it doesn't have two mentors assigned to it as of today, October 23 - 2015. The project will be included in the discussion of next iteration of GSoC/Outreachy, and is excluded from #Outreachy-11. Potential candidates are discouraged from submitting proposals to this task for #Outreachy-11 as it lacks mentors in this round.

@Parent5446 this task has been assigned to you. Do you plan on working on this or mentoring this for the upcoming Outreachy-13 round?

instead of changing the indexes for every member pages of a redirected category, couldn't there exist an index within target categories for listing the other category names that are redirected to it?
In that case, listing the content of the category would list all pages of the target category and of the source redirected categories, merged into a single list to sort.
This could however have an impact on performance if there are many redirected categories to list.

Note that the source category would still list their specific members (but to view them you have to visit these redirected categoties with redirect=no) which remain nidexed there and still need maintenance (using a job queue, or probably still preferably by using some auhtorized bots that may be paced down and will not run before the new redirect is accepted and not reverted) on all member pages to empty the contents of the redirected categories.

Note that most often, the redirected categories just come from an edit to rename it, while preserving its description and edit history into the new target category; however the member pages are still not recategorized. For this reason, renaming a category should still not create a new category with the old name but just the "#REDIRECT". it should better create by default a new category with a template showing a soft redirect by default, so that its members are still vieable in a single click, even if they are also listed in the merge list shown when viewing the target category.

Adding a hard redirect before the soft redirect template in the category description page should better delayed.

Or if possible, the #REDIRECT in a category should not be immediately followed when visiting it via any link on any page as long as it's not empty. (this does not require any edit on many articles and no change in the indexes on the database, just a small patch in MediaWiki to provide better navigation)

@Parent5446 this task has been assigned to you. Do you plan on working on this or mentoring this for the upcoming Outreachy-13 round?

I don't have time to work on it (my patch in Gerrit has been untouched for ages), but I can help mentor it since I remember most of the problems involved.

Looks like from the community wish survey results, that this feature is quite in high demand, see the updated task description :)

@Parent5446 How much work is remaining to be done? Would you be interested in mentoring this for GSOC 2017/ Outreachy Round 14?

@Parent5446 Hi! We are in the process of recruiting tasks suitable for volunteers from the community wishlist for the Wikimedia-Hackathon-2017. This task seems like a good fit, but I'm wondering even if it gets picked up would you be around to answer any questions someone might have? Also, if someone claims it, would it be a start over? The hackathon is in May b/w 19-21.

"Supposing category:A redirects to category:B.
Would it be feasible to automatically move all articles placed in cat:A into cat:B instead?
Alternatively, would it be possible to create a Specialpage that lists all categories that are redirects, so that a bot can do the moving?"

The "Alternatively" is already implemented on English Wikipedia, since 5 October 2009. {{Category redirect}} will add the redirect category to Category:Wikipedia non-empty soft redirected categories if it has any contents. The contents are moved by RussBot at the moment. According to Wikidata 35 other Wikipedias and 20 other WMF wikis have an equivalent category.

The "Alternatively" is already implemented on English Wikipedia, since 5 October 2009.

It’s implemented on all wikis since 2014: the API module query+allredirects (example query) has been added in T59057: API lacks a method to query redirects to a title, which allows querying all redirect categories – this includes empty ones as well, but the bot can loop over them and simply not move anything if the category is empty. (It’s not a special page as requested back in 2005, but the action API – which was invented in 2006 – is even better for bots.)