Suggestion: drop 'g' in git-describe suffix

hi,

the convention to use a 'g' in the output of git-describe, eg.

   [lilydev@haring lilypond]$ git describe --abbrev=39
   lilypond_2_9_7-g47778d2297276484c861fc7536da13feb2d5fe8

is confusing: the g is also a hex digit, and without reading the manual carefully, you'd think this is the commit g4777.

Proposal: why not use

   tag#sha1

or some other non-hex character.