Plugin install fails: pluginRoot prepended to source path causing doubled directory segment

[marlobello]

Bug Report

Summary

When installing a plugin from the microsoft-skills marketplace (e.g. azure-skills@skills), the CLI constructs an incorrect path by joining pluginRoot with a source value that already contains the full path prefix. This produces a doubled directory segment and the install fails with a directory-not-found error.

Steps to Reproduce

1. Run /plugin and install azure-skills@skills from the microsoft-skills marketplace.
2. Observe the error: directory not found.

Expected Behavior

Plugin installs successfully. The resolved path should be:

~/.cache/copilot/marketplaces/microsoft-skills/.github/plugins/azure-skills

Actual Behavior

The CLI looks for the plugin at:

~/.cache/copilot/marketplaces/microsoft-skills/.github/plugins/.github/plugins/azure-skills

Root Cause (Observed)

In marketplace.json for microsoft-skills, the metadata.pluginRoot is set to ./.github/plugins and each plugin entry's source field is ./.github/plugins/<plugin-name> (the full path from repo root). The CLI appears to join pluginRoot + source rather than treating source as repo-root-relative, resulting in the segment being appended twice.

Relevant marketplace.json snippet:

{
  "metadata": {
    "pluginRoot": "./.github/plugins"
  },
  "plugins": [
    {
      "name": "azure-skills",
      "source": "./.github/plugins/azure-skills"
    }
  ]
}

Workaround

Manually create a symlink at the doubled path pointing to the real plugin directory:

mkdir -p ~/.cache/copilot/marketplaces/microsoft-skills/.github/plugins/.github/plugins
ln -sf   ~/.cache/copilot/marketplaces/microsoft-skills/.github/plugins/azure-skills   ~/.cache/copilot/marketplaces/microsoft-skills/.github/plugins/.github/plugins/azure-skills

Environment

• OS: Linux
• Marketplace: microsoft-skills (marketplace version 1.0.0)
• Plugin: azure-skills (plugin version 1.0.1)
• Copilot CLI version: 1.0.10