feat(plugin): environment variable passing to plugins (Phase 3)

[gwpl]

Summary

Phase 3 of external plugin architecture (Issue #188). Builds on Phase 1 (#189) and Phase 2 (#190).

Passes GOG_* environment variables to plugins for integration with core CLI.

Environment Variables

Variable	Description	Example
GOG_CORE_VERSION	Version of gog CLI	0.9.0
GOG_CORE_PATH	Path to gog binary	/usr/bin/gog
GOG_CONFIG_PATH	Shared config file	~/.config/gogcli/config.json
GOG_PLUGIN_NAME	Plugin binary name	gog-docs-headings
GOG_PLUGIN_INVOKED_AS	User's command	gog docs headings
GOG_COLOR	Color preference	auto, always, never
GOG_OUTPUT_FORMAT	Output format	json, plain

Example Plugin Using Env Vars

#!/bin/bash
# Get the config path
config_path="$GOG_CONFIG_PATH"

# Check output format
if [[ "$GOG_OUTPUT_FORMAT" == "json" ]]; then
    echo '{"message": "hello"}'
else
    echo "Hello!"
fi

# Call back to core CLI
"$GOG_CORE_PATH" version

Example Output

$ gog env test
GOG Environment Variables:
GOG_CONFIG_PATH=/home/user/.config/gogcli/config.json
GOG_CORE_PATH=/usr/bin/gog
GOG_CORE_VERSION=0.9.0
GOG_PLUGIN_INVOKED_AS=gog env test
GOG_PLUGIN_NAME=gog-env-test

Changes

• internal/cmd/external.go - buildPluginEnv(), setEnvVar(), updated execExternal()
• internal/cmd/external_test.go - Tests for env var construction

Test plan

• Unit tests for setEnvVar (add, override)
• Unit tests for buildPluginEnv (expected vars present)
• Unit tests for findExternalCommandWithMatched (returns matched args)
• Manual test with shell script plugin printing env vars

Dependencies

Depends on Phase 1 (#189) and Phase 2 (#190)

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Part of #188

Generated with Claude Code

Co-Authored-By: Claude Opus 4.5 noreply@anthropic.com