[Rd] pointers on including SVN revision number in package info?

[Ben Bolker]

  I'm trying to keep debugging of a development package relatively sane.

  I see that some packages manage to incorporate what appears to be
Subversion (SVN) revision information in the package description; for
example,

> library(MASS)
> sessionInfo()$otherPkgs$MASS$Revision
[1] "$Rev: 3016 $"

  which looks like an auto-generated revision number.

  On the other hand, the rgl package (for example) appears to manually
encode the SVN revision in the package number:

> library(rgl)
> sessionInfo()$otherPkgs$rgl$Version
[1] "0.92.829"

  I'd love an automatic strategy, if possible, so I can be lazy about
updating the DESCRIPTION file every time I commit a change to SVN ...
I searched the R extensions manual (and the r-forge manual), but I'm
sure I could have missed something ...

  Or can people suggest other useful strategies for keeping track of
which development (micro-)version a random user might be working with?

 thanks,
  Ben Bolker