--working-dir option does not work when calling opam update

[voodoos]

Similar to #3807

On opam 2.1.3 on macos I observe the following behavior when trying to update a switch with some package pinned from directories:

❯ opam update --working-dir
<><> Updating package repositories ><><><><><><><><><><><><><><><><><><><><>  🐫 
[default] synchronised from https://opam.ocaml.org

<><> Synchronising development packages <><><><><><><><><><><><><><><><><><>  🐫 
[NOTE] Ignoring uncommitted changes in /Users/ulysse/tmp/dune (`--working-dir' not active).

I also observe unexpected behaviour when specifying the package to update:

❯ opam update dune
<><> Synchronising development packages <><><><><><><><><><><><><><><><><><>  🐫 
[NOTE] Ignoring uncommitted changes in /Users/ulysse/tmp/dune (`--working-dir' not active).
[dune.dev] synchronised (no changes)

❯ opam update --working-dir dune
<><> Synchronising development packages <><><><><><><><><><><><><><><><><><>  🐫 
Processing  1/1: [dune.dev: git]
[dune.dev] fetching sources failed: /Users/ulysse/tmp/dune/

[voodoos]

After discussing offline with @rjbou it turned out that I was not using opam correctly: to re-install (upgrade) a pinned package from the latest uncommited changes one simply has to run opam upgrade --working-dir [pkgs] without the update step.

[kit-ty-kate]

If opam update --working-dir without arguments should not be used, it should be shown as an error somewhere

[rjbou]

Yes, the message need to be updated for tis case to be more clear

[rjbou]

But using working-dir with no argument is not an error, it is a no-op.