rerun_except

rerun_except allows you to easily specify which files should not trigger a cargo rebuild, which can significantly cut down on unnecessary builds. In essence, this library inverts the normal way that you tell cargo about dependencies: cargo requires you to tell it which files should be tracked; rerun_except requires you to tell it which files should be ignored. The latter is safer, because if you add files to your project later they will automatically trigger a rebuild until and unless you explicitly inform rerun_except that they should be ignored.

rerun_except uses the ignore library to specify which files to ignore. You thus need to specify one or more globs in gitignore format which specifies which files to ignore: all other files (except those in ignore files such as .gitignore) will be tracked.

For example if you have the following file layout:

proj/
  .gitignore
  Cargo.toml
  src/
    lib.rs
  lang_tests/
    run.rs
    test1.lang
    test2.lang
  target/
   ...

and you do not want the two .lang files to trigger a rebuild then you would tell rerun_except to ignore lang_tests/*.lang. Assuming that the .gitignore file ignores the target/ directory, then rerun_except will also ignore the target directory. Note that adding a new file such as lang_tests/test3.lang will not trigger a rebuild (since it is covered by the ignore glob lang_tests/*.lang), but adding a new file such as build.rs will trigger a rebuild (since it is not covered by an ignore glob).

To use rerun_except in this manner you simply need to call rerun_except::rerun_except with an array of ignore globs in gitignore format as part of your build.rs file:

use rerun_except::rerun_except;

fn main() {
    rerun_except(&["lang_tests/*.lang"]).unwrap();
}

This will automatically communicate the necessary dependencies to cargo.