pidgin-latex: replace with SF one and fix
Merge pull request #4776 from abbradar/pidgin-latex

pidgin-latex: replace with SF one and fix
nixos/modules/services/monitoring/graphite.nix: don't create graphite user unconditionally

I'm not sure what exactly this user is needed for, i.e. under what circumstances
it must exist or not, but creating it unconditionally seems like the wrong thing
to do. I complained to @offlinehacker about this on Github, but got no response
for a week or so. I'm disabling the extraUsers bit to put out the fire, and now
hope that someone who actually knows about Graphite implements a proper solution
later.
nixos/modules/services/monitoring/graphite.nix: strip trailing whitespace
nix-prefetch-git: fix determinism with leaveDotGit

Add more files to the delete list:

 * .git/FETCH_HEAD
 * .git/ORIG_HEAD
 * .git/refs/remotes/origin/HEAD
 * .git/config

Further, remove all remote branches, remove tags not reachable from the
given 'rev', do a full repack and then garbage collect unreferenced
objects.

According to my testing, the result is fully deterministic. As in "any
change done to the upstream repo, ahead of 'rev', will not affect the
hash of the resulting 'clone'". Even changing the clone URL will not
change the output hash, because .git/config is removed.

A new version of git can of course change store format, but that's
unavoidable.

For big repositories, the repack operation may be a bit heavy. But as
far as I can see there is no cheaper way to determinism.