[bug-gsrc] Avoiding FTP/using HTTP in GSRC

[sbaugh]

Hi,

I'm trying to use GSRC to compile GNU software on a locked-down
corporate box that only has access to the internet through a corporate
HTTP/HTTPS proxy; all other outward connections are blocked.  I think
this is probably a common use case for GSRC.

I ran into a problem with initially downloading GSRC; I had to change
the checkout command mentioned on https://www.gnu.org/software/gsrc/ to:

  bzr checkout http://bzr.savannah.gnu.org/r/gsrc/trunk/ gsrc

to get an initial checkout of GSRC. It would be nice if this command was
already using http://, or at least the alternative command was mentioned
on that page. Note that http://bzr.savannah.gnu.org/gsrc/trunk/ does not
work.

Right now I have another problem: While most source tarballs seem to be
downloaded over HTTP, libffi (a dependency of GNU Guile) is downloaded
with FTP. So it is blocked by the corporate firewall. It would be nice
in gsrc had an HTTP tarball url that it could fall back to. I see that
libffi releases are also available on Github at
https://github.com/libffi/libffi/releases but I don't know if
downloading them from Github is too unsavory.

I am sure there are other packages that use FTP as well. It would be
nice if GSRC explicitly supported falling back to HTTP for such
packages.

I am also unsure about the best way to provide an alternative source
tarball for a package, to work around these issues for me specifically.

Thank you for the hard work! GSRC is otherwise amazing!