The default install-from-git.sh can install realgud into a site-lisp,
e.g /usr/local/share/emacs-site-lisp.

site-lisp directories and their subdirectories may be automatically
added to load path, in particular in Debian
/usr/local/share/emacs/site-lisp/ is added to load-path before emacs
system directories.  So realgud's common/buffer/info.el is loaded
before emacs's info.el

Adding this ".nosearch" file prevents emacs from adding realgud to the
load-path.