Make wasm-cc Envoy commit and registry URL configurable via environment variables

[Copilot]

Envoy CI needs to test against current commit ($GITHUB_SHA), and release branches require different Envoy versions. Currently, these values are hardcoded in MODULE.bazel and .bazelrc.

Changes

Template-based configuration

• MODULE.bazel.tpl - Parameterizes git_override blocks with ${ENVOY_COMMIT} for envoy, envoy_api, envoy_build_config, and envoy_mobile modules
• registry.bazelrc.tpl - Parameterizes registry URL with ${REGISTRY_URL}
• .bazelrc - Added try-import %workspace%/registry.bazelrc for generated config

Build infrastructure

• shared/build/Dockerfile - Install gettext-base (provides envsubst), add build args
• shared/build/build-entrypoint.sh - Generate config files from templates before build execution
• docker-compose-wasm.yaml - Pass environment variables as build args with defaults using YAML anchors

Usage

# Default (e1d1bcc84e310bc35d46bb2d78297159fc4f3e9f)
docker-compose -f docker-compose-wasm.yaml build

# CI with current commit
ENVOY_COMMIT=$GITHUB_SHA docker-compose -f docker-compose-wasm.yaml build

# Custom registry
REGISTRY_URL=https://custom.registry.com docker-compose -f docker-compose-wasm.yaml build

Default values:

• ENVOY_COMMIT: e1d1bcc84e310bc35d46bb2d78297159fc4f3e9f
• REGISTRY_URL: https://raw.githubusercontent.com/phlax/bazel-central-registry/b739c7fa56b971d695af9600b88099236dcfef76

Original prompt

Context

This is a follow-up to PR #1041 (#1041) which adds the http-filter-cc example using bzlmod.

The current implementation hardcodes the Envoy commit hash in MODULE.bazel via git_override and the registry URL in .bazelrc. This needs to be configurable for:

1. Envoy CI: When running tests from Envoy's CI, it should use the current Envoy commit ($GITHUB_SHA)
2. Release branches: May need different override configurations
3. Registry URL: Currently uses a specific registry hash, but should be overridable for testing and eventually use a fixed registry address

Required Changes

1. Create MODULE.bazel.tpl

Rename/convert MODULE.bazel to MODULE.bazel.tpl with ${ENVOY_COMMIT} placeholder in the git_override blocks:

git_override(
    module_name = "envoy",
    commit = "${ENVOY_COMMIT}",
    remote = "https://github.com/envoyproxy/envoy",
)

git_override(
    module_name = "envoy_api",
    commit = "${ENVOY_COMMIT}",
    remote = "https://github.com/envoyproxy/envoy",
    strip_prefix = "api",
)

2. Create registry.bazelrc.tpl

Create a new template file with the registry URL placeholder:

common --registry=${REGISTRY_URL}

3. Update .bazelrc

Remove the phlax registry line and add a try-import for the generated registry config:

try-import %workspace%/registry.bazelrc

Keep the other two registries (bcr.bazel.build and envoyproxy/toolshed) as they are static.

4. Update Dockerfile

Add build args and envsubst processing:

ARG ENVOY_COMMIT
ARG REGISTRY_URL

# Generate config files from templates
RUN envsubst '${ENVOY_COMMIT}' < MODULE.bazel.tpl > MODULE.bazel \
    && if [ -f registry.bazelrc.tpl ]; then \
           envsubst '${REGISTRY_URL}' < registry.bazelrc.tpl > registry.bazelrc; \
       fi

5. Update docker-compose.yml

Pass through the new environment variables as build args:

args:
  GITHUB_TOKEN: "${GITHUB_TOKEN}"
  ENVOY_COMMIT: "${ENVOY_COMMIT:-e1d1bcc84e310bc35d46bb2d78297159fc4f3e9f}"
  REGISTRY_URL: "${REGISTRY_URL:-https://raw.githubusercontent.com/phlax/bazel-central-registry/b739c7fa56b971d695af9600b88099236dcfef76}"

Reference

Base the changes on the files from PR #1041: #1041

The current hardcoded values to use as defaults:

• ENVOY_COMMIT: e1d1bcc84e310bc35d46bb2d78297159fc4f3e9f
• REGISTRY_URL: https://raw.githubusercontent.com/phlax/bazel-central-registry/b739c7fa56b971d695af9600b88099236dcfef76

This pull request was created from Copilot chat.

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