I just hit a problem when trying to read the diff manual. I ran "info diff" and it wasn't found. After struggling to check whether I had the manual installed and finding that it was installed (as /usr/share/info/diffutils.info.gz), and checking that that file had a dir entry in it, I ran
$ sudo install-info /usr/share/info/diffutils.info.gz /usr/share/info/dir which appeared to work with no problems, but in fact the dir file had not been created. After doing "sudo touch /usr/share/info/dir" and re-running install-info, I managed to run "info diff" successfully. I suggest that install-info should create the file if it did not exist already, or at the least give a warning about the file not existing.
