I think we currently have an issue where the builder scripts for several
download approaches are very numerous, svn-multi-download is probably
the extreme example as that's used for the numerous texlive packages.

I noticed this when wondering why bayfront is spending so much time
substituting svn-multi-download files from data.guix.gnu.org, and it's
probably taking up extra space in the data.guix.gnu.org database too.

These commits should address the issue in svn-multi-fetch, svn-fetch,
hg-fetch and git-fetch (although this issue doesn't affect users of
builtin:git-download).  The main change is to pass the hash through to
the builder as an environment variable, rather than generating a
different builder script for each different hash.

I've also restructured the code to try and avoid this problem in the
future.  While there was a comment about the intent to not duplicate the
builder scripts, it's too easy to miss.  By moving the builder to it's
own procedure and moving the comment to the call site, it'll be clearer
when a new source of variation is added.


Christopher Baines (4):
  svn-download: Reduce svn-multi-fetch builder duplication.
  svn-download: Reduce svn-fetch builder duplication.
  hg-download: Reduce builder duplication.
  git-download: Reduce builder duplication.

 guix/git-download.scm | 123 +++++++++++---------
 guix/hg-download.scm  | 127 +++++++++++---------
 guix/svn-download.scm | 264 +++++++++++++++++++++++-------------------
 3 files changed, 291 insertions(+), 223 deletions(-)