template_processor: Allow to skip files or directories

[fetzerch]

Templated file names can now contain expressions to control if the file or directory should be generated or skipped. If the expression evaluates to a non-empty string, that string is used as file or directory name. If the expression evaluates to an empty string the generation of that file or directory is skipped.

This can be used to provide custom files in the source repo that are not overridden by a template.

For example the directory:
addon/depends/windows/{{ "mingw" if not config.nomingw }} is not generated if 'nomingw': True is added to the config.

@garbear is this what you meant with your comment in kodi-game/game.libretro.2048#6?
I fear in its current form the template engine cannot skip a directory based on the existence of a file in the source repo. With this change, we would just need to add depends/windows/2048/CMakeLists.txt and remove depends/windows/mingw/*. The other changes from https://github.com/kodi-game/game.libretro.2048/pull/6/files (appveyor, common/2048/CMakeLists.txt) would remain as they are, but that shouldn't be an issue.

Maybe also interesting for @Rechi.

[Rechi]

depends/common/{{ game.name }}/windows-deps.txt may also have to be removed/not added in that case.

[coveralls]

Coverage increased (+0.03%) to 78.562% when pulling 8deedd6 on skip_dirs into c674a45 on master.

[fetzerch]

While refactoring the code, I noticed that this should be already possible: A file is not generated if its content is empty. I'll update this change accordingly.

[fetzerch]

@Rechi Is it still the case that 2048 should be compiled without mingw on windows? Then I'll merge this as well.

[fetzerch]

There's a bit more todo: (see https://github.com/kodi-game/game.libretro.2048/pull/6/files)

• depends/common/2048/CMakeLists.txt
• depends/windows/2048/2048.txt
• appveyor.yml

[Rechi]

Although it would be nice to get rid of mingw, there is no use if it is only done for one.
Additionally one would have to keep the cmake project in sync.