File targets can't be directories

[richfitz]

This is currently by design, but will need to be dealt with. Need to distinguish between cases where directories represent list targets (#8) to when they are something like an unpacked shapefile and pointing at a single file makes no sense.

For the first case, just need to implement list targets :). For the second case, need to recursively hash the whole directory I think. That has the potential to be very slow though, so probably worth holding off until different hash options are available.

[krlmlr]

Also need to keep in mind that all files inside this directory depend on that directory:

targets:
  ./some_dir:
    command: fill_directory(target_name)

  result:
    command: compute_result("some_dir/some_file/in/dir.txt")

The result target would trigger the some_dir target.

Do you think it's possible to add this extension to the current code base without stirring it up too much?

[richfitz]

It would be good to see if it could be made to work. This was always a huge frustration working with make, and I think it's a common use case. I think it could be incorporated into the current code without causing too much havoc

[krlmlr]

Also, rules may cause conflicts now:

targets:
  ./some_dir:
    command: fill_directory(target_name)

  ./some_dir/subdir:
    command: fill_directory(target_name)

I'd expect the two rules to be incompatible, because some_dir is fully described by the first rule. You still should be able to depend on files and dir under some_dir, though.