Adding bzlmod support document (#1214)

This markdown file maintains the current status of our bzlmod
implementation. Created section in README and linked to the bzlmod doc.

1 files changed, 37 insertions, 0 deletions

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+# Bzlmod support
+
+## `rule_python` `bzlmod` support
+
+- Status: Beta
+- Full Feature Parity: No
+
+Some features are missing or broken, and the public APIs are not yet stable.
+
+## Configuration
+
+The releases page will give you the latest version number, and a basic example.  The release page is located [here](/bazelbuild/rules_python/releases).
+
+## What is bzlmod?
+
+> Bazel supports external dependencies, source files (both text and binary) used in your build that are not from your workspace. For example, they could be a ruleset hosted in a GitHub repo, a Maven artifact, or a directory on your local machine outside your current workspace.
+>
+> As of Bazel 6.0, there are two ways to manage external dependencies with Bazel: the traditional, repository-focused WORKSPACE system, and the newer module-focused MODULE.bazel system (codenamed Bzlmod, and enabled with the flag `--enable_bzlmod`). The two systems can be used together, but Bzlmod is replacing the WORKSPACE system in future Bazel releases.
+> -- <cite>https://bazel.build/external/overview</cite>
+
+## Examples
+
+We have two examples that demonstrate how to configure `bzlmod`.
+
+The first example is in [examples/bzlmod](examples/bzlmod), and it demonstrates basic bzlmod configuration.
+A user does not use `local_path_override` stanza and would define the version in the `bazel_dep` line.
+
+A second example, in [examples/bzlmod_build_file_generation](examples/bzlmod_build_file_generation) demonstrates the use of `bzlmod` to configure `gazelle` support for `rules_python`.
+
+## Feature parity
+
+This rule set does not have full feature partity with the older `WORKSPACE` type configuration:
+
+1. Multiple python versions are not yet supported, as demonstrated in [this](examples/multi_python_versions) example.
+2. Gazelle does not support finding deps in sub-modules.  For instance we can have a dep like ` "@our_other_module//other_module/pkg:lib",` in a `py_test` definition.
+
+Check ["issues"](/bazelbuild/rules_python/issues) for an up to date list.