Added settings to give a different output filename than index.html

[j0nes2k]

With this option it is possible to specify another output filename for the generated gallery files than the default index.html. This is useful if the directory index is already used otherwise.

[saimn]

Hi @j0nes2k ,
I wonder if we could combine this with another feature, which would be to allow to render multiple templates, adding a flexible way to specify templates / output files. This could be done with a setting which would map a template name to an output file name. Something like:

templates = {
    'index.html': 'index.html' // template: output file
} 

or maybe a list of tuples

templates = [
    ('index.html', 'index.html') // template: output file
]

What do you think ?

[j0nes2k]

I agree that this approach would solve the basic problem for me, too.
However I am not sure how big these changes will be as it probably goes
quite deep into the rendering mechanism. Can you estimate the effort and
potential pitfalls?

[saimn]

Hmm, looping on the list of (template, output_file) can be easily done in the write method, but the tricky point is how to handle the urls.
Currently albums have an url which is the album name + optionally the 'index.html' useful if you want to browse the gallery without a webserver. I don't know if these urls should be different for different templates. I don't have a clear use case now, there was a proposition to do something like that in #74 but the code has changed a lot since that and this PR didn't not address the url issue. Any suggestions are welcome, otherwise we can go on with your PR and we will later if a more evolved feature is needed.

[saimn]

This could be directly settings['output_filename'] (instead of adding an extra parameter).

[j0nes2k]

I also think that support for multiple output files is generally a good idea and can be used for a lot of other advanced features (like tag pages, recent changes etc). I would suggest to have a look at this problem again when developing features that require these changes.

[saimn]

Ok, let's start with this. Thanks for the contribution :)