The gitplugins.conf file is a list of all the plugins you want to manage (install, upgrade...) with the format:

    'local/mailtest' => [
        'path' => '/local/mailtest', // mandatory ; path from the moodle root
        'gitrepository' => 'https://github.com/michael-milette/moodle-local_mailtest', // mandatory
        'gitbranch' => '', // optional ; git branch (incompatible with gitrevision)
        'gitrevision' => '', // optional ; precise git revision (hash or tag)  (incompatible with gitbranch)
    ],

You can then launch php gitplugins.php with one of the options:

• --gen-config generates a sample gitplugins.conf file
• --check checks the consistency of 'gitplugins.conf'
• --diag displays a diagnostic of all declared plugins
• --status launches a git status on each declared plugin
• --install installs all plugins that are not already present (git clone)
• --upgrade upgrades all plugins already installed (git fetch + git checkout)
• --cleanup "removes" all plugins in an inconsistent state (by renaming them, so restoration is possible)
• --gen-exclude generates a chunk of lines to insert in your .git/info/exclude file

"Cleaned" repositories are renamed to <orig-name>.back-<timestam>, so you can easily find and restore them if needed.