RE: Backwards compatibility: \compressMusic, \scaleDurations, WHY WHY WHY

[Steve Dunlop]

> This has been discussed numerous times on the mailing list.  Check the 
> archives.
> 
> Handling syntax changes such as \compressMusic --> \scaleDurations are
> easily handled by convert-ly, since there is no change in structure of
> the input file.  Simply use the following command:
> 
> $ convert-ly -e oldfile.ly
> 
> and your file's \version declaration will be updated along with the syntax.
> 

You don't get it.  If you have an archive like Mutopia, where there are
thousands of files and dozens of contributors, and mixed dependencies on
versions, running conver-ly doesn't work.

It doesn't work because two people working on the same file may not have
the same version of Lilypond.  You can't get dozens of volunteer
contributors to upgrade to the latest version all at once every time a
new version comes out by snapping your fingers.

It doesn't work because the same file may be included in two separate
projects which use different versions of Lilypond because they rely on
features and syntax much more difficult to fix than the example I cite. 
In some cases one of the projects may be in a "freeze" where only minor
changes from proofreading are being admitted, and something major like a
Lilypond upgrade would be problematic because the whole project would
have to be re-proofread to be sure things like spacing weren't adversely
affected.

It doesn't work because the person who needs the change may not be the
maintainer of the file, and the maintainer of the file may have other
things to do besides run convert-ly on some old project.

Unless all you ever want Lilypond to be is a program used by individuals
typesetting a handful of their favorite works, rather than, say, the
lingua Franca of the open content classical music movement.

Steve