texlive: add comments, whitespace cleanup

Fixes #34490.  The FIXME has been long obsolete.

pkgs/tools/typesetting/tex/texlive/default.nix

@@ -37,8 +37,10 @@ let
     /* # beware: the URL below changes contents continuously
       curl http://mirror.ctan.org/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.xz \
         | xzcat | uniq -u | sed -rn -f ./tl2nix.sed > ./pkgs.nix */
-    orig = import ./pkgs.nix tl; # XXX XXX XXX FIXME: the file is probably too big now XXX XXX XXX XXX XXX XXX
-    removeSelfDep = lib.mapAttrs (n: p: if p ? deps then p // { deps = lib.filterAttrs (dn: _: n != dn) p.deps; } else p);
+    orig = import ./pkgs.nix tl;
+    removeSelfDep = lib.mapAttrs
+      (n: p: if p ? deps then p // { deps = lib.filterAttrs (dn: _: n != dn) p.deps; }
+                         else p);
     clean = removeSelfDep (orig // {
       # overrides of texlive.tlpdb
 
@@ -112,6 +114,10 @@ let
       urls = args.urls or (if args ? url then [ args.url ] else
               map (up: "${up}/${urlName}.tar.xz") urlPrefixes
             );
+
+      # Upstream refuses to distribute stable tarballs, so we host snapshots on IPFS.
+      # Common packages should get served from the binary cache anyway.
+      # See discussions, e.g. https://github.com/NixOS/nixpkgs/issues/24683
       urlPrefixes = args.urlPrefixes or [
         http://146.185.144.154/texlive-2017
         # IPFS GW is second, as it doesn't have a good time-outing behavior