Motivation for this change

I was trying the dev branch of ipfs v0.11 and found that the services.ipfs.autoMigrate option was broken. The daemon tries to download and run a golang binary that is improperly linked and can't even be patchelfed, not to mention the pre-start script fails before it even gets to that point, because of the repo version mismatch.

The best approach I see right now is do the migration automatically ourselves, rather than relying on the daemon's fault-prone internal method. The first step is to detect the actual ipfs repo version by looking at /var/lib/ipfs/version, then determining the version the installed binary wants (hard, since ipfs version --all refuses to run, IIRC, which may be an upstream bug that needs to be filed). Finally, we can run the appropriate X-to-Y binaries, in order, provided in the new ipfs-migrator package, to get to the correct version, then launch the daemon.

Things done

I've disabled the autoMigrate option in services.ipfs. I'm including a build of the migration tools so that re-adding the autoMigrate feature is easier on whomever ends up fixing the option.

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • Linux
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.