Cannot update Bolt since 1.2.x

[diktyo2001]

Win XP, I update Bolt writing in git shell : composer update.
Now it returns :

Loading composer repositories with package information
Updating dependencies (including require-dev)
- Updating doctrine/common (2.4.0-RC4 => v2.4.1)
[RuntimeException]
The .git directory is missing from E:\__misccms\boltcms\vendor\doctrine\com
mon, see http://getcomposer.org/commit-deps for more information

As I know nothing about composer and git, any help would be appreciated.

Thanks

Petros