--debug documentation, output

[Karl Berry]

It seems --debug is not documented at all, in the help message or the
manual.  Can you tell me the meaning of the argument?  I tried perusing
in the source but it didn't come quickly.

Meanwhile, running
makeinfo --dvi --debug=1 line.tex
now outputs the entire tree and some 1600 lines of other output before
getting to the execution.  That's ok, I guess, although it seems awfully
verbose without asking for maximum debugging.  But in any case, the
execution of the subprogram is nearly impossible to find unless you know
it's there, being the one line:
texi2dvi|--dvi|--debug|line.tex
after all the other stuff, and immediately followed by the texi2dvi
expansions.

Can you make that debug output start with some indication, e.g.,

EXEC texi2dvi|--dvi|--debug|line.tex

(A clue that it is being run via exec.)

Thanks,
k