Fix the contribution instructions on tindallgrams.net

[ianfixes]

From http://tindallgrams.net/contribute:

The biggest task by far is editing the Tindallgrams themselves. To contribute in this way, first find a Tindallgram that needs to be edited in one of the sources.

Rather than dig through the sources, it would be easier to just dig through a nice list you've already generated. Similar to the one found here:
http://seanredmond.github.io/Tindallgrams/

It should list all known Tindallgrams (which you must have, since you know there are 464), with an indication of which ones have not yet been converted.

[seanredmond]

I'd almost forgotten about that list! I think this is somewhat linked to #4 in that what would be most useful is 1) a list of untranscribed memos with 2) an easy link to the original in a PDF. The first alone would suffice, but both together would make it easier to contribute?

[ianfixes]

My original intention was for this issue to be a pull request that implements this, but

• poking around in the ruby code gave me the impression that a lot of interrelated things are happening, that I didn't want to accidentally break
• I wasn't sure of the proper way to get the list of already-converted tgrams

[seanredmond]

If you look at one of the year indexes (1966, say), that's a good start. With the addition of some frontmatter, these just contain liquid tag markup:

{% tgindex year 1966 %}

Here tgindex calls a plugin tgindex.rb with the two parameters indicating, as you can guess, "make a year index for 1966".

The entire list of Tindallgrams is loaded from the YAML file:

@grams = YAML.load_file('_data/tindallgrams-index.yaml')['tindallgrams']

The filter method then filters this list according to the desired index type (currently year or source) and render_index generates the table. Before it's generated, the get_published method is called to make a list of already-transcribed Tindallgrams (by looking for files that actually exist). So, when the table is generated, links can be made to the transcribed version when they exist by seeing if they exist in that list.

Making an index of "done" or "to-do" Tindallgrams, would only require adding on to tgindex so that it can generate the desired pages and then adding the new page templates. I would suggest enabling the tags:

{% tgindex transcribed true %}
{% tgindex transcribed false %}

The filter method would then just have to use get_published to filter the done memos in or out.

If you want to give this a go, don't worry about breaking anything -- we'll fix any problems before merging.