lilypond-book with html: "Output would overwrite input file" error

[Jonathan Kulp]

Hi All,

I'm trying to understand exactly how lilypond-book works with html 
source files.  I'm running Ubuntu 8.04 with 2.11.56.

As suggested in the manual, I've specifed an output directory ( 
--output=DIR).  So let's say my source file is 
~/Documents/Composition/Piano/filename.html

and my output directory is

~/Documents/Composition/Piano/Book

What I've found is that the first invocation of lilypond-book on the 
source html file works fine, but the next time I run it after making 
changes to the sourcefile, I get an error saying "lilypond-book: error: 
Output would overwrite input file; use --output."

What I've deduced from this is that lilypond-book must first make a copy 
of my source file and put it in the output directory, then use that as 
the input file.  Is this correct?  Because when I remove the html file 
from the output directory and run lilypond-book on filename.html (in the 
directory above the output directory), it runs its course and creates 
the desired output.  My question is this: shouldn't the "input file" 
really be the one that's NOT in the output directory?  In other words, 
why doesn't lilypond-book take the command-line argument as the input 
file instead of the html file that it has copied (apparently) to the 
output directory?

I've made a workaround to the problem by adding a line to my lilybook 
script saying first to remove the html file from the output directory, 
but it seems to me that the program should use the argument of the 
lilypond-book command as the input file and overwrite the html file 
inside the output directory instead of returning errors saying that 
output would overwrite the input file.

Can anyone offer insight?  This sort of thing never happens when I'm 
using lilypond-book on the .itely for the GDP.  Is it a bug, or is it 
designed this way to avoid deleting files inadvertently?

Best,

Jonathan
--
Jonathan Kulp
http://www.jonathankulp.com