Indeed, two variables is a bit overkill, but the OPAMUTF8MSGS variable was kept mostly for backwards-compatibility, and also because I needed a (default) intermediate level with the arrows, but without the camel emojis. On second thought, maybe adding a possible value (i.e. 'always', 'never', 'auto' or 'partial') would be best. And the documentation should indeed specify that it's only for OPAM-generated messages, excluding metadata that may be printed.

Mr. Herr:
indeed, in the case of 'opam update', it's not completely self-explanatory. But I made sure that it is in the case of package actions, which is the one that matters:


    % opam install core_bench --show
    The following actions would be performed:
      ↘  downgrade sexplib       112.24.00 to 112.17.00  [required by core_bench]
      ↘  downgrade pa_ounit      112.24.00 to 112.17.00  [required by core_bench]
      ↘  downgrade bin_prot      112.24.00 to 112.17.00  [required by core_bench]
      ↘  downgrade pa_test       112.24.00 to 111.08.01  [required by core]
      ↻  recompile uri           1.8.0                   [uses sexplib]
      ↻  recompile ipaddr        2.6.1                   [uses sexplib]
      ↻  recompile ezjsonm       0.4.1                   [uses sexplib]
      ↻  recompile cstruct       1.5.0                   [uses sexplib]
      ↘  downgrade custom_printf 112.24.00 to 112.17.00  [required by core]
      ↻  recompile pa_bench      112.06.00               [uses pa_ounit]
      ↘  downgrade typerep       112.24.00 to 112.17.00  [uses bin_prot]
      ↻  recompile ocsigenserver 2.5                     [uses ipaddr]
      ↻  recompile cow           1.2.1                   [uses ezjsonm, uri]
      ↻  recompile conduit       0.7.2                   [uses sexplib]
      ↘  downgrade core_kernel   112.24.00 to 112.17.00  [uses bin_prot]
      ↻  recompile eliom         4.1.0                   [uses ipaddr]
      ↻  recompile cohttp        0.15.0                  [uses sexplib]
      ∗  install   core          112.17.00               [required by core_bench]
      ↻  recompile github        0.9.4                   [uses cohttp, uri]
      ∗  install   textutils     112.17.00               [required by core_bench]
      ∗  install   core_bench    112.17.00             
    ===== ∗  3   ↻  11   ↘  7 =====
    
the glyphs make the information easier to skim through, but the actions are written in text; the summary only shows the glyphs, but you may use the full list as a key to their meaning.
And if you have compatibility problems or just don't like it, set OPAMUTF8 to "never" and you'll get good old plain text:


    % OPAMUTF8=never opam install core_bench --show
    The following actions would be performed:
      - downgrade sexplib       112.24.00 to 112.17.00      [required by core_bench]
      - downgrade pa_ounit      112.24.00 to 112.17.00      [required by core_bench]
      - downgrade bin_prot      112.24.00 to 112.17.00      [required by core_bench]
      - downgrade pa_test       112.24.00 to 111.08.01      [required by core]
      - recompile uri           1.8.0                       [uses sexplib]
      - recompile ipaddr        2.6.1                       [uses sexplib]
      - recompile ezjsonm       0.4.1                       [uses sexplib]
      - recompile cstruct       1.5.0                       [uses sexplib]
      - downgrade custom_printf 112.24.00 to 112.17.00      [required by core]
      - recompile pa_bench      112.06.00                   [uses pa_ounit]
      - downgrade typerep       112.24.00 to 112.17.00      [uses bin_prot]
      - recompile ocsigenserver 2.5                         [uses ipaddr]
      - recompile cow           1.2.1                       [uses ezjsonm, uri]
      - recompile conduit       0.7.2                       [uses sexplib]
      - downgrade core_kernel   112.24.00 to 112.17.00      [uses bin_prot]
      - recompile eliom         4.1.0                       [uses ipaddr]
      - recompile cohttp        0.15.0                      [uses sexplib]
      - install   core          112.17.00                   [required by core_bench]
      - recompile github        0.9.4                       [uses cohttp, uri]
      - install   textutils     112.17.00                   [required by core_bench]
      - install   core_bench    112.17.00             
    ===== 3 to install | 11 to recompile | 7 to downgrade =====
    
This will also be the case, of course, if your current locale isn't UTF8.


Best,
Louis Gesbert - OCamlPro

> - Daniel Bünzli, 27/03/2015 21:24 -
> Le vendredi, 27 mars 2015 à 20:52, Mr. Herr a écrit :
> > I would have voted against the unicode graphics,  
> 
> There's no voting process but you can disable them, see:  
>   
> https://github.com/ocaml/opam/issues/2065#issuecomment-83232580
> 
> Btw. Louis I think the two level scheme is a little bit overkill and more complex that it should be, you should really keep it to a single variable. That two-level mechanism seem to have been design to work around issues in OS level support for unicode glyphs and it doesn't sound like a good idea. Also the description of OPAMUTF8 is misleading, UTF-8 characters may be output since opam files are UTF-8 encoded and AFAIK you don't transcode any output of the tool to ASCII when OPAMUTF8 is `never` (e.g. opam file messages: fields).  
> 
> Best,
> 
> Daniel
> 
> 
> 
>