Add documentation. (#1)

README.md

@@ -0,0 +1,101 @@
+<!--
+Copyright (c) Ansible Project
+GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
+SPDX-License-Identifier: GPL-3.0-or-later
+-->
+
+# GitHub Action for testing importing an Ansible collection with the Galaxy importer
+
+[![Linting](https://github.com/ansible-community/github-action-test-galaxy-import/actions/workflows/linting.yml/badge.svg)](https://github.com/ansible-community/github-action-test-galaxy-import/actions/workflows/linting.yml)
+[![REUSE](https://github.com/ansible-community/github-action-test-galaxy-import/actions/workflows/reuse.yml/badge.svg)](https://github.com/ansible-community/github-action-test-galaxy-import/actions/workflows/reuse.yml)
+
+A composite GitHub Action that allows to test importing a built Ansible collection with the [Galaxy importer](https://github.com/ansible/galaxy-importer) in GitHub Actions CI/CD workflows.
+
+While this action can be used directly in workflows, we suggest to use the [bundled shared workflow](#bundled-shared-workflow).
+
+This action is covered by the [Ansible Code of Conduct](https://docs.ansible.com/ansible/latest/community/code_of_conduct.html).
+
+## Usage
+
+To use the action, add the following step to your workflow file (for example `.github/workflows/galaxy-import.yml`):
+
+```yaml
+- name: Test collection import
+  uses: ansible-community/github-action-test-galaxy-import@main
+  with:
+    artifact-path: /path/to/foo-bar-1.0.0.tar.gz
+```
+
+## Options
+
+The follow options can be provided to this GitHub Action.
+
+### `python-version`
+
+The Python version to use.
+
+Note that 3.12 currently does not work due to https://github.com/madpah/requirements-parser/issues/88.
+
+**(DEFAULT: `3.11`)**
+
+### `ansible-core-version`
+
+The branch of tag name of ansible-core to install.
+This is assumed to exist in https://github.com/ansible/ansible.
+
+**(DEFAULT: `stable-2.16`)**
+
+### `collection-requirements-path`
+
+Path to a Galaxy requirements file. If present, these collections will be installed.
+
+### `artifact-path`
+
+Path to the collection's build artifact (tarball).
+
+**(REQUIRED)**
+
+## Bundled shared workflow
+
+This GitHub Action bundles a shared workflow, [test-galaxy-import.yml](https://github.com/ansible-community/github-action-test-galaxy-import/blob/main/.github/workflows/test-galaxy-import.yml), which allows you to build a collection and test importing it with the Galaxy importer.
+
+```yaml
+name: import-galaxy
+'on':
+  # Run CI against all pushes (direct commits, also merged PRs) to main and the stable-* branches, and all Pull Requests
+  push:
+    branches:
+      - main
+      - stable-*
+  pull_request:
+
+jobs:
+  import-galaxy:
+    permissions:
+      contents: read
+    name: Import collection with Galaxy importer
+    uses: ansible-community/github-action-test-galaxy-import/.github/workflows/test-galaxy-import.yml@main
+```
+
+If your collection's root (where `galaxy.yml` is) is in a subdirectory of the repository, use the `subdirectory` option:
+
+```yaml
+jobs:
+  import-galaxy:
+    permissions:
+      contents: read
+    name: Import collection with Galaxy importer
+    uses: ansible-community/github-action-test-galaxy-import/.github/workflows/test-galaxy-import.yml@main
+    with:
+      subdirectory: ansible_collections/foo/bar
+```
+
+Please check out the workflow for other supported options.
+
+## License
+
+This action is primarily licensed and distributed as a whole under the GNU General Public License v3.0 or later.
+
+See [LICENSES/GPL-3.0-or-later.txt](https://github.com/ansible-community/github-action-test-galaxy-import/blob/main/COPYING) for the full text.
+
+All files have a machine readable `SDPX-License-Identifier:` comment denoting its respective license(s) or an equivalent entry in an accompanying `.license` file. This conforms to the [REUSE specification](https://reuse.software/spec/).

action.yml

@@ -17,6 +17,7 @@ inputs:
   ansible-core-version:
     description: >-
       The branch of tag name of ansible-core to install.
+      This is assumed to exist in https://github.com/ansible/ansible.
     default: 'stable-2.16'
   collection-requirements-path:
     description: >-