Remove lint warning 56

OPAM_LAST_ENV means that it's no longer necessary to limit setenv to
compiler packages.

master_changes.md

@@ -147,6 +147,7 @@ users)
   * [BUG] Fix linting packages from repository with tarred repositories, the file in temporary repository was no more avaiable when lint is done [#5068 @rjbou]
   * Update repository package filename display [#5068 @rjbou]
   * E67: check checksums only for vcs urls [#4960 @rjbou]
+  * W56: detection removed, since `OPAM_LAST_ENV` allows reliable reverting [#5417 @dra27]
 
 ## Repository
   * When several checksums are specified, instead of adding in the cache only the archive by first checksum, name by best one and link others to this archive [#4696 rjbou]

src/state/opamFileTools.ml

@@ -651,9 +651,13 @@ let t_lint ?check_extra_files ?(check_upstream=false) ?(all=false) t =
                       used norm)
                   bad_os_arch_values)
        (bad_os_arch_values <> []));
+    (* Retired, since `OPAM_LAST_ENV` allows environment updates to be reliably
+       reverted. *)
+(*
     cond 56 `Warning
       "It is discouraged for non-compiler packages to use 'setenv:'"
       (t.env <> [] && not (has_flag Pkgflag_Compiler t));
+*)
     cond 57 `Error
       "Synopsis and description must not be both empty"
       (t.descr = None || t.descr = Some OpamFile.Descr.empty);

tests/reftests/lint.test

@@ -591,21 +591,6 @@ depexts: ["foo"] { arch = "i486" }
 ${BASEDIR}/lint.opam: Errors.
              error 55: Non-normalised OS or arch string being tested: "i486 (use x86_32 instead)"
 # Return code 1 #
-### : W56: It is discouraged for non-compiler packages to use 'setenv:'
-### <lint.opam>
-opam-version: "2.0"
-synopsis: "A word"
-description: "Two words."
-authors: "the testing team"
-homepage: "egapemoh"
-maintainer: "[email protected]"
-license: "ISC"
-dev-repo: "hg+https://[email protected]"
-bug-reports: "https://nobug"
-setenv: [ idoit="anyway" ]
-### opam lint ./lint.opam
-${BASEDIR}/lint.opam: Warnings.
-           warning 56: It is discouraged for non-compiler packages to use 'setenv:'
 ### : E57: Synopsis and description must not be both empty
 ### <lint.opam>
 opam-version: "2.0"