Thanks to Daniel Stone's efforts, libinput is now on gitlab. For a longer explanation on the move from the old freedesktop infrastructure (cgit, bugzilla, etc.) to the gitlab instance hosted by freedesktop.org, see this email.
All open bugs have been migrated from bugzilla to gitlab too, the documentation has been updated acccordingly, and we're ready to go. The new base URL for libinput in gitlab is: https://gitlab.freedesktop.org/libinput/.