Hammer is a tool to manage big projects that consist of multiple git repositories, which are loosely coupled.
It provides global sync of all managed repositories, global operations for all or a subset of the repositories, and integration with Gerrit Code Review.
The outstanding feature is support for consistent changes in multiple repositories.
On Debian-based systems, install:
$ apt-get install libgit-repository-perl libxml-mini-perl liburi-perl
On RPM-based systems such as Fedora or RHEL you need to install:
$ dnf install perl-Git-Repository-Plugin-AUTOLOAD perl-URI perl-CPAN perl-Test perl-File-pushd
$ cpan install XML::Mini::Document
On Arch Linux, these packages need to be installed from the AUR by a method of your choice:
$ yay -S perl-git-repository perl-xml-mini perl-uri
ham updates many repositories at once in the background, typically using ssh as a secure transport. It is therefore required to use ssh-agent to allow for non-interactive ssh-authentication.