DOC: Updated README

Author: pastewka

README.md

@@ -1,12 +1,13 @@
 # DiscoverVersion
 
-This package automatically discover version information for a package. It
-tries the following option to get the version of the package:
+This package automatically discovers version information for a package. It
+tries the following options to get the version of the package (in order):
 
+* Check the `DISCOVER_VERSION` environment variable
 * Inspect a `PKG-INFO` file
 * Ask `git`, if the current directory is a git-repository
 * Ask `importlib.metadata`
- 
+
 It is intended as a lightweight replacement for
 `setuptools_scm`.
 
@@ -26,7 +27,7 @@ dynamic = ['version']
 dependencies = ['DiscoverVersion']
 ```
 
-The add the following to your toplevel `__init__.py`:
+Then add the following to your toplevel `__init__.py`:
 
 ```python3
 from DiscoverVersion import get_version
@@ -37,6 +38,58 @@ __version__ = get_version('my_package_name')
 Note that it is important to hard code the name of your package in the call
 to `get_version`.
 
+## Environment Variable Override
+
+You can override version discovery by setting the `DISCOVER_VERSION` environment
+variable. This is useful in CI/CD pipelines where git may not be available or
+when building in isolated environments:
+
+```bash
+DISCOVER_VERSION=1.2.3 python -m build
+```
+
+## Command Line Interface
+
+DiscoverVersion provides a CLI for discovering and outputting version information:
+
+```bash
+# Print the discovered version
+python -m DiscoverVersion
+
+# Or use the entry point
+discover-version
+
+# Write version to a Python file
+python -m DiscoverVersion --write-to version.py
+
+# Write version to a plain text file (useful for Meson builds)
+python -m DiscoverVersion --write-to version.txt --plain
+
+# Specify a fallback version if discovery fails
+python -m DiscoverVersion --fallback 0.0.0
+
+# Disable specific discovery methods
+python -m DiscoverVersion --no-git --no-env
+```
+
+### CI/CD Example (GitHub Actions)
+
+Here's an example of using DiscoverVersion in a GitHub Actions workflow with
+`cibuildwheel`:
+
+```yaml
+- name: Get version from DiscoverVersion
+  id: get_version
+  run: |
+    pip install DiscoverVersion
+    echo "version=$(python -m DiscoverVersion)" >> $GITHUB_OUTPUT
+
+- name: Build wheels
+  uses: pypa/cibuildwheel@v2
+  env:
+    CIBW_ENVIRONMENT: DISCOVER_VERSION=${{ steps.get_version.outputs.version }}
+```
+
 ## Tests
 
 Before being able to run tests, you need to execute