Allow posts to be organised in an arbitrary tree of subdirectories

[r14c]

your docs say that this should be possible. probably some omission or maybe its actually broken.

repro steps:

1. create a brand new elmstatic project
2. mkdir _posts/foo
3. mv _posts/2019-01-02-another-post.md _posts/foo
4. observe that elmstatic says ENOENT: no such file or directory, open '_site/foo/rss.xml'

elmstatic build
Building the site
  Compiling layouts
Success!     

    Tag ──────┬──> elm.js
    Page ─────┤
    Photo ────┤
    Photos ───┤
    Post ─────┤
    Posts ────┘

  Generating pages
  Generating posts
  Generating tag pages
  Cleaning out the output path (_site)
  Writing HTML
  Generating feeds

ENOENT: no such file or directory, open '_site/foo/rss.xml'

[alexkorban]

You also need to have _pages/foo with at least one page in it, then Elmstatic will be able to build it.

[r14c]

having a bunch of dummy pages just to make the builder happy seems less than ideal. for example, i keep my posts organized by year so i have to create a page for each year. an about page isn't even relevant for this kind of thing. seems like it would be reasonable to have elmstatic create the foo directory in this case if it doesn't exist yet.

[r14c]

i can understand wanting to keep things simple and opinionated. i'm happy to contribute here, but if you'd prefer to keep things as they are i can go do my own thing instead.

[alexkorban]

I prefer to keep the current behaviour for now as it's nontrivial to combine arbitrary subdirs in _posts with the existing support for subsections. I'll keep this issue open as an enhancement for future reference.