Track Ninja's dyndeps feature

[ndmitchell]

Ninja 1.7 is adding dyndeps (will be in the Ninja manual once it's done), along with examples of extracting a tarball and compiling Fortran. I should make documentation on the website of how to do that, and also support dyndeps in the Ninja build.

[Mathnerd314]

Ninja documentation link: https://github.com/bradking/ninja/blob/features-for-fortran/doc/manual.asciidoc#dynamic-dependencies

It's not clear if it will actually be in 1.7.

[Mathnerd314]

The tarball example is like the zip file in #421 (comment).

I'm not sure about the Fortran example; it seems like it would fscan all the files on every build, while in fact you only need to fscan the changed files.

[ndmitchell]

Yep, if it goes in, I'd aim to support it. I find the dyndeps thing a little confusing at first glance - it seems like a weird primitive to have added (I assume its a restricted version of monadic dependencies in some way).

[Mathnerd314]

Dynamic implicit inputs can be replicated by a function that reads the dyndep file and calls need.

Dynamic implicit outputs are more interesting; they're a provide-like operation, with the semantics that modifying a provide-d file will re-run the provider, unless the provider is the thing that modified it.

[Ericson2314]

ninja-build/ninja#1521 wow it actually landed! The ranks of monadic build systems have grown.