🚀 go-pugleaf

This is probably more of a question than a bug report.

While trying to figure out why I was receiving error messages 
with line numbers that were 3 too high, I noticed something
I don't understand in gtbl (version 1.04, though I've looked at the code
for 1.05 and I don't think this has changed).  If I type "gtbl < /dev/null" 
or "gtbl - < /dev/null" I get the output:

    .if !\n(.g .ab GNU tbl requires GNU troff.
    .if !dTS .ds TS
    .if !dTE .ds TE

which seem to be the three extra lines.  If I type "gtbl -v - < /dev/null",
I get:

    .if !\n(.g .ab GNU tbl requires GNU troff.
    .if !dTS .ds TS
    .if !dTE .ds TE
    .lf 1 -

which includes the .lf request to reset the line number.  The last
test was suggested by looking at the gtbl 1.05 code, which suggests that
the .lf request is added if there is a named input file on the command line,
or if there is a "-" on the command line and it is NOT the first argument 
(perhaps the motivation here is an assumption that if "-" is not the
first argument, then it is preceded by named input files, and
you need the .lf requests to identify the different sources of input).

So my question is, does anyone know the rationale for not resetting the
line number when you believe you're reading only standard input?
-- 

John Jorgensen		jorgnsn@qucis.queensu.ca	(613) 545 6784
Systems Programmer, Dept. of Computing Science, Queen's University