When we want to see what commands are listed in `command-list.txt` but
not installed, we currently include lines that refer to guides, e.g.
`gitattributes` or `gitcli`.
Let's not include those lines, as they are not referring to commands.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>