Add "generate release notes" class/function/command

[remcotolsma]

Currently we generate the release notes quite late in the version command:

The version command does several things, but this is not immediately clear to users beforehand.

• git pull
• Working tree status (git status)
• git branch --show-current
• Check tagnames without v prefix.'
• Run Composer script preversion
• Check composer.json type property.
• Check composer outdated
• Check non-comparable Composer package versions (dev-*)
• Check package.json version property
• Check WordPress plugin file headers from *.php files
• Check multiple WordPress plugins in working directory
• Ask user for bump method (patch, minor, major)
• Compose changelog
• Set plugin file header version
• Set theme style.css header version
• Set Stable tag in readme.txt header
• Set version in package.json
• Run Composer script version
• Git commit changes (git commit)
• Git tag (git tag)
• Git push (git push)
• Run Composer script postversion

• Explain how the version command works #10

pronamic-cli/src/VersionCommand.php

Lines 319 to 393 in 33351cf

	/**
	* If CHANGELOG.md check if new version is part of it?
	*/
	$file_changelog_md = $cwd . '/CHANGELOG.md';
	if ( ! is_readable( $file_changelog_md ) ) {
	$io->note( 'It is a good idea to keep track of the changes in a `CHANGELOG.md` file: https://keepachangelog.com/.' );
	}
	if ( is_readable( $file_changelog_md ) ) {
	/**
	* Remote URL.
	*
	* @link https://github.com/cookpete/auto-changelog/blob/0991f17ce936a9db490e2ad1a04121755038b78d/src/remote.js
	*/
	$process = $this->new_process( 'git remote get-url origin', $cwd );
	$process_helper->mustRun( $output, $process );
	$url = $process->getOutput();
	$components = $this->parse_git_url( $url );
	$url_repository = 'https://' . $components['host'] . '/' . $components['organisation'] . '/' . $components['repository'];
	$changelog = new Changelog( $file_changelog_md );
	if ( ! $changelog->has_entry( $new_version ) ) {
	$changelog_entry = $changelog->new_entry( $new_version );
	$changelog_entry->url = $url_repository;
	$changelog_entry->version_previous = $version;
	$changelog_entry->body .= $this->add_git_log( $cwd, $version, $output, $url_repository );
	if ( isset( $composer_json ) ) {
	$changelog_entry->body .= $this->generate_composer_json_changelog( $cwd, $version, $output );
	}
	$choice = '';
	$iteration = 0;
	while ( 'ok' !== $choice ) {
	$iteration++;
	$io->title( 'Changelog' );
	$io->text( $changelog_entry->body );
	$choice = $io->choice(
	'🔁 ' . $iteration . ': Is the above changelog OK?',
	[
	'ok',
	'subl',
	],
	'subl'
	);
	if ( 'subl' === $choice ) {
	$process = $this->new_process( 'subl -', $cwd, null, $changelog_entry->body );
	$process_helper->mustRun( $output, $process );
	$changelog_entry->body = $process->getOutput();
	}
	}
	$changelog_entry_string = trim( $changelog_entry->render() ) . "\n\n";
	$changelog->insert( $changelog->get_insert_position(), $changelog_entry_string );
	$changelog->save();
	}
	}

It would be more convenient if we could generate and display the changelog before the "Ask user for bump method". Based on the generated changelog, a user can more easily choose the desired bump method.