Directive to reference macros from WORKSPACE

[jayconrod]

#480 will add the ability for update-repos to write repository rules to a macro in a separate .bzl file.

Gazelle currently reads repository rules declared in WORKSPACE in order to discover custom repository names and known prefixes. This information is used for dependency resolution. If repositories are declared in a macro, this information will no longer be available (though #132 would be a useful escape hatch).

We should have a directive that tells Gazelle to look for repository rules in a macro in a .bzl file. It should be possible to repeat this directive, since there may be multiple macros.

# gazelle:repository_macro repos.bzl%go_repositories

This is mainly useful for the fix and update commands, but bonus points if update-repos can update repository rules in the corresponding macros without additional command line arguments instead of writing copies to WORKSPACE.

[ifoox]

Hi Jay, do you intend to make a release of Gazelle with this included any time soon? (I see the last release is from Feb).

[jayconrod]

Soon, yes. #477 is the main release blocker. I've gotten sidetracked with some toolchain compatibility issues in new versions of Bazel, but I expect to come back to this soon.