Cygwin lilypond v2.12.2-1: -dgui flag fails with DOS path

[Lawrence Mayer]

Cygwin Lilypond v2.12.2-1 has the following bug:

lilypond.exe -dgui <path>

requires that <path> be in Unix format (e.g. /cygdrive/c/Music/test.ly). If 
<path> is in DOS format (e.g. C:\Music\test.ly), no log file is generated, nor 
does any log info appear in the console.

This bug is especially significant, since an Explorer context menu entry, e.g.

HKLM,"SOFTWARE\Classes\LilyPond\shell\generate\command",,,"""C:\cygwin\bin
\lilypond.exe"" -dgui ""%1"""

feeds lilypond a DOS path (the index "%1" is in DOS format). Thus, double-
clicking on a .ly file, or right-clicking and choosing "Generate PDF...", will 
fail to generate a log file.

This bug depends on the -dgui flag. If -dgui is omitted, it doesn't matter if 
<path> is in Unix or DOS format.

This bug is not present in Cygwin Lilypond v2.10.33-1, which *requires* DOS 
paths with -dgui. In v2.10.33-1, a Unix path with -dgui generates a log file in 
the console's working directory rather than the directory of the .ly file 
(where the .ps and .pdf files are generated).

Greetings,
Larry

Version details:
Cygwin Lilypond v2.12.2-1 is not yet on Cygwin's server. It was installed 
together with guile-1.8.5-1 and libguile17-1.8.5-1 , all downloaded from
http://download.linuxaudio.org/lilypond/binaries/cygwin/
Cygwin version: 1.5.25-15 (latest stable release)