Unable to upgrade to irmin 0.9.9 with opam

[MagnusS]

When I update/upgrade from 0.9.8 I get this error:

$ opam upgrade
The following actions will be performed:
  - upgrade   git        1.6.2 to 1.7.0
  - upgrade   irmin      0.9.8 to 0.9.9
  - recompile irmin-unix 0.9.4                          [uses git, irmin]
===== 1 to recompile | 2 to upgrade =====
Do you want to continue ? [Y/n] y

=-=- Gathering sources =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
[git] Archive in cache
[irmin] Archive in cache
[default] https://opam.ocaml.org/archives/irmin-unix.0.9.4+opam.tar.gz downloaded

=-=- Processing actions -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
-> removed   irmin-unix.0.9.4
-> removed   irmin.0.9.8
-> removed   git.1.6.2
-> installed git.1.7.0
[ERROR] The compilation of irmin failed at "make".
Processing  5/6: [irmin: ocamlfind remove]
#=== ERROR while installing irmin.0.9.9 =======================================#
# opam-version 1.2.2
# os           linux
# command      make
# path         /home/mag/.opam/system/build/irmin.0.9.9
# compiler     system (4.01.0)
# exit-code    2
# env-file     /home/mag/.opam/system/build/irmin.0.9.9/irmin-2518-60459a.env
# stdout-file  /home/mag/.opam/system/build/irmin.0.9.9/irmin-2518-60459a.out
# stderr-file  /home/mag/.opam/system/build/irmin.0.9.9/irmin-2518-60459a.err
### stdout ###
# [...]
# /home/mag/.opam/system/bin/ocamlfind ocamldep -package cstruct -package dolog -package ezjsonm -package git -package hex -package lwt -package mstruct -package ocamlgraph -package stringext -package tc -package uri -modules lib/git/irmin_git.ml > lib/git/irmin_git.ml.depends
# /home/mag/.opam/system/bin/ocamlfind ocamlc -c -g -annot -bin-annot -short-paths -I lib -package cstruct -package dolog -package ezjsonm -package git -package hex -package lwt -package mstruct -package ocamlgraph -package stringext -package tc -package uri -w A-4-41-44 -I lib/git -I lib -o lib/git/irmin_git.cmo lib/git/irmin_git.ml
# + /home/mag/.opam/system/bin/ocamlfind ocamlc -c -g -annot -bin-annot -short-paths -I lib -package cstruct -package dolog -package ezjsonm -package git -package hex -package lwt -package mstruct -package ocamlgraph -package stringext -package tc -package uri -w A-4-41-44 -I lib/git -I lib -o lib/git/irmin_git.cmo lib/git/irmin_git.ml
# File "lib/git/irmin_git.ml", line 642, characters 36-37:
# Error: Signature mismatch:
#        ...
#        The field `length' is required but not provided
#        The field `string' is required but not provided
#        The field `cstruct' is required but not provided
# Command exited with code 2.
### stderr ###
# E: Failure("Command ''/usr/bin/ocamlbuild' lib/irmin.cma lib/irmin.cmxa lib/irmin.a lib/irmin.cmxs lib/mem/irmin-mem.cma lib/mem/irmin-mem.cmxa lib/mem/irmin-mem.a lib/mem/irmin-mem.cmxs lib/git/irmin-git.cma lib/git/irmin-git.cmxa lib/git/irmin-git.a lib/git/irmin-git.cmxs lib/fs/irmin-fs.cma lib/fs/irmin-fs.cmxa lib/fs/irmin-fs.a lib/fs/irmin-fs.cmxs lib/http/irmin-http.cma lib/http/irmin-http.cmxa lib/http/irmin-http.a lib/http/irmin-http.cmxs lib/unix/irmin-unix.cma lib/unix/irmin-unix.cmxa lib/unix/irmin-unix.a lib/unix/irmin-unix.cmxs bin/main.native -tag debug' terminated with error code 10")
# make: *** [build] Error 1

=-=- Error report -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
The following actions were aborted
  - install irmin-unix 0.9.4
The following actions failed
  - install irmin 0.9.9
The following changes have been performed
  - remove  irmin      0.9.8         
  - remove  irmin-unix 0.9.4         
  - upgrade git        1.6.2 to 1.7.0

[samoht]

should be git 1.7.1

[samoht]

See https://github.com/ocaml/opam-repository/pull/4677