j0k@MBP:~/Sites/f43.me$ composer up
Loading composer repositories with package information
Updating dependencies (including require-dev)
- Updating j0k3r/graby-site-config (1.0.3 => 1.0.4)
Checking out cf088ca2100eeec3f230cc187a5b489e61fe97f1
Writing lock file
Generating autoload files
PHP Fatal error: Call to undefined method Composer\Package\CompletePackage::getFullPrettyVersion() in /Users/j0k/.composer/vendor/pyrech/composer-changelogs/src/OperationHandler/UpdateHandler.php on line 58
PHP Stack trace:
PHP 1. {main}() /usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar:0
PHP 2. require() /usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar:24
PHP 3. Composer\Console\Application->run($input = *uninitialized*, $output = *uninitialized*) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/bin/composer:43
PHP 4. Symfony\Component\Console\Application->run($input = *uninitialized*, $output = *uninitialized*) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/src/Composer/Console/Application.php:84
PHP 5. Composer\Console\Application->doRun($input = *uninitialized*, $output = *uninitialized*) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/vendor/symfony/console/Symfony/Component/Console/Application.php:126
PHP 6. Symfony\Component\Console\Application->doRun($input = *uninitialized*, $output = *uninitialized*) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/src/Composer/Console/Application.php:147
PHP 7. Symfony\Component\Console\Application->doRunCommand($command = *uninitialized*, $input = *uninitialized*, $output = *uninitialized*) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/vendor/symfony/console/Symfony/Component/Console/Application.php:195
PHP 8. Symfony\Component\Console\Command\Command->run($input = *uninitialized*, $output = *uninitialized*) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/vendor/symfony/console/Symfony/Component/Console/Application.php:874
PHP 9. Composer\Command\UpdateCommand->execute($input = *uninitialized*, $output = *uninitialized*) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/vendor/symfony/console/Symfony/Component/Console/Command/Command.php:257
PHP 10. Composer\Installer->run() phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/src/Composer/Command/UpdateCommand.php:140
PHP 11. Composer\EventDispatcher\EventDispatcher->dispatchScript($eventName = *uninitialized*, $devMode = *uninitialized*, $additionalArgs = *uninitialized*, $flags = *uninitialized*) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/src/Composer/Installer.php:336
PHP 12. Composer\EventDispatcher\EventDispatcher->doDispatch($event = *uninitialized*) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/src/Composer/EventDispatcher/EventDispatcher.php:91
PHP 13. call_user_func:{phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/src/Composer/EventDispatcher/EventDispatcher.php:151}(*uninitialized*, *uninitialized*) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/src/Composer/EventDispatcher/EventDispatcher.php:151
PHP 14. Pyrech\ComposerChangelogs\ChangelogsPlugin->postUpdate($event = *uninitialized*) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/src/Composer/EventDispatcher/EventDispatcher.php:151
PHP 15. Pyrech\ComposerChangelogs\Outputter->getOutput() /Users/j0k/.composer/vendor/pyrech/composer-changelogs/src/ChangelogsPlugin.php:76
PHP 16. Pyrech\ComposerChangelogs\Outputter->createOperationOutput($output = *uninitialized*, $operation = *uninitialized*) /Users/j0k/.composer/vendor/pyrech/composer-changelogs/src/Outputter.php:61
PHP 17. Pyrech\ComposerChangelogs\OperationHandler\UpdateHandler->getOutput($operation = *uninitialized*, $urlGenerator = *uninitialized*) /Users/j0k/.composer/vendor/pyrech/composer-changelogs/src/Outputter.php:92
Fatal error: Call to undefined method Composer\Package\CompletePackage::getFullPrettyVersion() in /Users/j0k/.composer/vendor/pyrech/composer-changelogs/src/OperationHandler/UpdateHandler.php on line 58
Call Stack:
0.0116 410496 1. {main}() /usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar:0
0.0120 412248 2. require('phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/bin/composer') /usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar:24
0.0587 3501888 3. Composer\Console\Application->run(???, ???) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/bin/composer:43
0.0612 3818560 4. Symfony\Component\Console\Application->run(???, ???) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/src/Composer/Console/Application.php:84
0.0622 3943288 5. Composer\Console\Application->doRun(???, ???) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/vendor/symfony/console/Symfony/Component/Console/Application.php:126
0.0635 4065184 6. Symfony\Component\Console\Application->doRun(???, ???) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/src/Composer/Console/Application.php:147
0.0638 4066104 7. Symfony\Component\Console\Application->doRunCommand(???, ???, ???) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/vendor/symfony/console/Symfony/Component/Console/Application.php:195
0.0638 4066576 8. Symfony\Component\Console\Command\Command->run(???, ???) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/vendor/symfony/console/Symfony/Component/Console/Application.php:874
0.0647 4070960 9. Composer\Command\UpdateCommand->execute(???, ???) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/vendor/symfony/console/Symfony/Component/Console/Command/Command.php:257
0.3706 9571456 10. Composer\Installer->run() phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/src/Composer/Command/UpdateCommand.php:140
135.7863 256004064 11. Composer\EventDispatcher\EventDispatcher->dispatchScript(???, ???, ???, ???) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/src/Composer/Installer.php:336
135.7863 256004504 12. Composer\EventDispatcher\EventDispatcher->doDispatch(???) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/src/Composer/EventDispatcher/EventDispatcher.php:91
135.7957 256110168 13. call_user_func:{phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/src/Composer/EventDispatcher/EventDispatcher.php:151}(???, ???) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/src/Composer/EventDispatcher/EventDispatcher.php:151
135.7957 256110280 14. Pyrech\ComposerChangelogs\ChangelogsPlugin->postUpdate(???) phar:///usr/local/Cellar/composer/1.0.0-alpha10/libexec/composer.phar/src/Composer/EventDispatcher/EventDispatcher.php:151
135.7957 256110352 15. Pyrech\ComposerChangelogs\Outputter->getOutput() /Users/j0k/.composer/vendor/pyrech/composer-changelogs/src/ChangelogsPlugin.php:76
135.7957 256110880 16. Pyrech\ComposerChangelogs\Outputter->createOperationOutput(???, ???) /Users/j0k/.composer/vendor/pyrech/composer-changelogs/src/Outputter.php:61
135.7958 256112040 17. Pyrech\ComposerChangelogs\OperationHandler\UpdateHandler->getOutput(???, ???) /Users/j0k/.composer/vendor/pyrech/composer-changelogs/src/Outputter.php:92
j0k@MBP:~/Sites/f43.me$
I checked my composer version (which was installed using homebrew) and I got this version: Composer version 1.0.0-alpha10 2015-04-14 21:18:51
which seems quite old but it's the latest release.
Maybe you should add a verification on the Composer version to see what you can or cannot do.