Depend on directories in repo rules (recursively)

[matts1]

Description of the feature request:

We have two repo rules internally that depend on whole directories.

We have a rust binary that needs to generate a repository. Because of that, it can't depend on a toolchain, and we have to it in a repo rule.

In order to build the rust binary, we need our repo rule to depend on.

build_rust_binary = rule(
    attrs = dict(srcs = attr.label_list(...))
)

src/main.rs
src/foo/bar.rs
...

At the moment, we need to write build_rust_binary(srcs=["src/main.rs", "src/foo/bar.rs", ...]). However, that means that if we add a new file src/foo/baz.rs, for example, it won't trigger a rebuild, and it may or may not actually build successfully, depending on the implementation.

We have similar issues with another repo rule that depends on a directory, where each directory in the input corresponds to a directory in the output.

I'd like to be able to specify a directory as a label for inputs, so any changes to the transitive closure of the direcotry will trigger a rebuild.

Which category does this issue belong to?

External Dependency

What underlying problem are you trying to solve with this feature?

Ensure that rebuilds are triggered when a directory is modified (or any subdirectory)

Which operating system are you running Bazel on?

Linux

What is the output of bazel info release?

6.2.0

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

No response

What's the output of git remote get-url origin; git rev-parse master; git rev-parse HEAD ?

No response

Have you found anything relevant by searching the web?

No response

Any other information, logs, or outputs that you want to share?

No response

[meteorcloudy]

https://docs.google.com/document/d/17RZKMuMjAIgNfFdrsLhqNsMTQDSS-BBA-S-fCSBPV7M/edit should help

[Wyverald]

dupe of #20952 (which is fixed and will be in 7.1.0)