Cli versioning: experimental flags handling

[rjbou]

Prints a warning when it is used, and it update the manpage with an Experimental annotation.

And a fix on default cli flags

[rjbou]

Outputs

With these flags modified to be experimental, and some of them deprecated:

• Simple flag
  • --confirm-level yes, --confirm-level unsafe-yes
  • --confirm-level ask, --confirm-level no deprecated since 2.1
• Combined flags
  • opam list --installed, opam list --available
  • opam list --all, opam list --roots deprecated since 2.1
• Enum flags
  • opam show --empty-fiels
  • opam show --raw deprecated since 2.1
  • opam show --where-xp deprecated since 2.1 & replaced by --where

The output is

### mk_flag experimental
$ opam show ago --empty-fields
[WARNING] Flag --empty-fields is experimental, there is no guarantee that it will be kept; avoid using it in scripts.

### mk_flag exprimenal remove 2.1
$ opam show ago --raw
opam: --raw was removed in version 2.1 of the opam CLI, but version 2.2 has been requested.
      This flag was experimental, so the behaviour may be removed completely in a future release.

### mk_flag experimental -> 2.1 & replaced
$ opam show ago --where-xp
opam: --where-xp was removed in version 2.1 of the opam CLI, but version 2.2 has been requested. It was experimental, use --where instead.

### mk_vflag_all experimental -> 2.1
$ opam list ago --all
opam: --all was removed in version 2.1 of the opam CLI, but version 2.2 has been requested.
      This flag was experimental, so the behaviour may be removed completely in a future release.

### mk_vflag_all experimental -> 2.1 multiple
$ opam list ago --all --roots
opam: --all and --installed-roots were all in 2.1, and were all removed by version 2.1 of the opam CLI, but version 2.2 has been requested.
      --all and --installed-roots were experimental, so the behaviour may be removed completely in a future release.

### mk_vflag_all experimental -> 2.1 & valid
$ opam list ago --all --base --pinned
opam: --all was removed in version 2.1 of the opam CLI, but version 2.2 has been requested.
      This flag was experimental, so the behaviour may be removed completely in a future release.

### mk_vflag_all experimental -> 2.1 multiple & valid
$ opam list ago --all --roots --base --pinned
opam: --all and --installed-roots were all in 2.1, and were all removed by version 2.1 of the opam CLI, but version 2.2 has been requested.
      --all and --installed-roots were experimental, so the behaviour may be removed completely in a future release.

### mk_flag_all experimental
$ opam list ago --installed
[WARNING] --installed is experimental, there is no guarantee that it will be kept; avoid using it in scripts.

### mk_flag_all experimental multiple
$ opam list ago --installed --available
[WARNING] --installed and --available are experimental, there is no guarantee that they will be kept; avoid using them in scripts.

### mk_flag_all experimental && valid
$ opam list ago --installed --base --pinned
[WARNING] --installed is experimental, there is no guarantee that it will be kept; avoid using it in scripts.
# No matches found

### mk_flag_all experimental multiple & valid
$ opam list ago --installed --available --base --pinned
[WARNING] --installed and --available are experimental, there is no guarantee that they will be kept; avoid using them in scripts.
# No matches found

### mk_enum experimental -> 2.1
$ opam config var switch --confirm-level ask
opam: The option ask for --confirm-level was removed in version 2.1 of the opam CLI, but version 2.2 has been requested.
      This flag was experimental, so the behaviour may be removed completely in a future release.

### mk_enum experimental -> 2.1 multiple
$ opam config var switch --confirm-level ask --confirm-level no
opam: The options ask and no for --confirm-level were all in 2.1, and were all removed by version 2.1 of the opam CLI, but version 2.2 has been requested.
      The options ask and no for --confirm-level was experimental, so the behaviour may be removed completely in a future release.

### mk_enum experimental
$ opam config var switch --confirm-level yes
[WARNING] The option yes for --confirm-level is experimental, there is no guarantee that it will be kept; avoid using it in scripts.

### mk_enum experimental multiple
$ opam config var switch --confirm-level yes --confirm-level unsafe-yes
[WARNING] The options yes and unsafe-yes for --confirm-level are experimental, there is no guarantee that they will be kept; avoid using them in scripts.