Create a commit for every plugin update.

git-commit-after-plugin-update.php

<?php
/**
 * Plugin Name: Commit on Update
 * Plugin Author: Joshua David Nelson
 **/

defined( 'ABSPATH' ) or die( 'Nope!' );

class Commit_On_Update {

	/**
	 * The version prior to update.
	 *
	 * @since 1.0.0
	 *
	 * @var string|bool
	 */
	var $prev_version = false;

	/**
	 * The version after the update.
	 *
	 * @since 1.0.0
	 *
	 * @var string|bool
	 */
	var $new_version = false;

	/**
	 * The name of the thing being updated.
	 *
	 * @since 1.0.0
	 *
	 * @var string|bool
	 */
	var $name = false;

	/**
	 * The final commit message.
	 *
	 * @since 1.0.0
	 *
	 * @var string|bool
	 */
	var $commit_message = false;

	/**
	 * The commit author.
	 *
	 * @since 1.0.0
	 *
	 * @var string
	 */
	var $author = 'Joshua Nelson <josh@joshuadnelson.com>';

	/**
	 * Get the party started.
	 *
	 * @since 1.0.0
	 */
	function init() {

		// Grab the plugin information before it updates
		// upgrader_process_complete
		add_filter( 'upgrader_source_selection', array( $this, 'get_previous_version_before_upgrade' ), 10, 4 );

		// After we've updated, make the commit
		add_filter( 'upgrader_post_install', array( $this, 'commit_after_update' ), 10, 3 );

	}

	/**
	 * Store some information on the plugin/theme before being updated.
	 *
	 * @since 1.0.0
	 *
	 * @param string $source
	 * @param string $remote_source
	 * @param object $object
	 * @param array $hook_extra
	 *
	 * @return string $source
	 */
	function get_previous_version_before_upgrade( $source, $remote_source, $object, $hook_extra ) {

		if( ! isset( $hook_extra['plugin'] ) )
			return $source;

		// Get the plugin version before the update and log it
		$this->prev_version = isset( $object->skin->plugin_info['Version'] ) ? $object->skin->plugin_info['Version'] : $this->get_plugin_version_from_hook_extra( $hook_extra );

		// Get the plugin name
		$this->name = isset( $object->skin->plugin_info['Name'] ) ? $object->skin->plugin_info['Name'] : false;

		return $source;

	}

	/**
	 * Fallback method of extracting plugin version.
	 *
	 * @since 1.0.0
	 *
	 * @param array $hook_extra
	 *
	 * @return string
	 */
	function get_plugin_version_from_hook_extra( $hook_extra ) {

		$version = 'Unknown';
		if( ! isset( $hook_extra['plugin'] ) ) {
			return $version;
		}

		$plugin_data = $this->get_plugin_data( WP_PLUGIN_DIR . '/' . $hook_extra['plugin'] );
		$plugin_version = isset( $plugin_data['Version'] ) ? $plugin_data['Version'] : 'Unknown';

		return $plugin_version;

	}

	/**
	 * A wrapper function for the WordPress function.
	 *
	 * @since 1.0.0
	 *
	 * @param string $path
	 *
	 * @return array
	 */
	function get_plugin_data( $path ) {

		$data = get_plugin_data( $path, false, false );

		return $data;

	}

	/**
	 * After a successful update, commit the changes.
	 *
	 * @since 1.0.0
	 *
	 * @param bool $boolean
	 * @param array $hook_extra
	 * @param string $result
	 *
	 * @return bool
	 */
	function commit_after_update( $boolean, $hook_extra, $result ) {

		if( ! isset( $hook_extra['plugin'] ) || ! isset( $result['destination_name'] ) )
			return $boolean;

		// Get new version, post update
		$plugin_data = $this->get_plugin_data( WP_PLUGIN_DIR . '/' . $hook_extra['plugin'] );

		if( ! isset( $plugin_data['Name'] ) || ! isset( $plugin_data['Version'] ) )
			return $boolean;

		// New Version
		$this->new_version = $plugin_data['Version'];

		// Plugin Name fallback
		if( ! $this->name )
			$this->name = $plugin_data['Name'];

		// Add the plugin folder to the git stage
		$folder = '"' . WP_PLUGIN_DIR . '/' . $result['destination_name'] . '"';

		// Commit Message
		$this->commit_message = 'Update Plugin: ' . $this->name . ' from ' . $this->prev_version . ' to ' . $this->new_version;

		// Soft reset to avoid commit anything else
		$this->execute_command( 'git reset --soft' );

		// Add the folder to stage all the changes
		$this->execute_command( 'git add --all ' . $folder );

		// Commit the changes - for some reason this isn't working?
		$this->execute_command( 'git commit -m "' . $this->commit_message . '" --author="' . $this->author . '" -- ' . $folder );

		return $boolean;

	}

	/**
	 * Execute the shell command.
	 *
	 * @since 1.0.0
	 *
	 * @param string $command
	 */
	function execute_command( string $command ) {

		system( $command );

	}

}

global $_commit_on_update;
$_commit_on_update = new Commit_On_Update;
$_commit_on_update->init();