pkg: lock is stat'ing the current directory like an opam repository

[emillon]

I noticed that when dune pkg lock runs, it looks for files in the current directory with a naming scheme similar to an opam-repository:

newfstatat(AT_FDCWD, "/home/etienne/src/dune/packages/ocaml/ocaml.4.09.2", 0x7ffe320108b0, 0) = -1 ENOENT (No such file or directory)

  % time     seconds  usecs/call     calls    errors syscall                          
  ------ ----------- ----------- --------- --------- ----------------                 
   49.56    0.037018           0     74266     56713 newfstatat                       
   33.63    0.025115           0     56689     56688 readlink       

That's a lot of system time, and I don't think we're expecting to see these files to be here.

NB this is from dune pkg lock in the dune tree.

[emillon]

(I'll investigate to see where these calls come from)

[emillon]

Interesting, it comes from:

      OpamFile.OPAM.read_from_string
        contents
        ~filename:(Path.to_string path |> OpamFilename.of_string |  > OpamFile.make)

Then opam tries to determine the realpath of that argument, and does so by stat'ing the whole directory tree.

[rgrinberg]

Ouch. I suppose we can just get rid of it here.