Warn if GNU patch is not detected during opam update

.github/workflows/ci.ml

@@ -360,7 +360,7 @@ let main_test_job ~analyse_job ~build_linux_job ~build_windows_job:_ ~build_macO
   let host = host_of_platform platform in
   let ocamlv = "${{ matrix.ocamlv }}" in
   job ~oc ~workflow ?section ~runs_on:(Runner [runner]) ~env:[("OPAM_TEST", "1")] ~matrix ~needs ("Test-" ^ name_of_platform platform)
-    ++ only_on MacOS (install_sys_packages ["coreutils"] ~descr:"Install gnu coreutils" [MacOS])
+    ++ only_on MacOS (install_sys_packages ["coreutils"; "gpatch"] ~descr:"Install gnu coreutils" [MacOS])
     ++ checkout ()
     ++ only_on Linux (run "Install bubblewrap" ["sudo apt install bubblewrap"])
     ++ cache Archives

.github/workflows/main.yml

@@ -322,7 +322,7 @@ jobs:
       OPAM_TEST: 1
     steps:
     - name: Install gnu coreutils
-      run: brew install coreutils
+      run: brew install coreutils gpatch
     - name: Checkout tree
       uses: actions/checkout@v4
     - name: src_ext/archives and opam-repository Cache

src/core/opamSystem.ml

@@ -1633,6 +1633,24 @@ let translate_patch ~dir orig corrected =
   end;
   close_in ch
 
+let patch_cmd = lazy begin
+  match OpamStd.Sys.os () with
+  | OpamStd.Sys.OpenBSD
+  | OpamStd.Sys.FreeBSD -> "gpatch"
+  | _ -> "patch"
+end
+
+let is_gpatch_available = lazy begin
+  let patch_cmd = Lazy.force patch_cmd in
+  let r = OpamProcess.run (make_command ~name:"patch" patch_cmd ["--version"]) in
+  match OpamProcess.is_success r, r.OpamProcess.r_stdout with
+  | true, full::_ when
+      OpamStd.String.is_prefix_of ~from:0 ~full "GNU patch " ->
+    true
+  | _ ->
+    false
+end
+
 let patch ?(preprocess=true) ~dir p =
   if not (Sys.file_exists p) then
     (OpamConsole.error "Patch file %S not found." p;
@@ -1645,12 +1663,7 @@ let patch ?(preprocess=true) ~dir p =
     else
       p
   in
-  let patch_cmd =
-    match OpamStd.Sys.os () with
-    | OpamStd.Sys.OpenBSD
-    | OpamStd.Sys.FreeBSD -> "gpatch"
-    | _ -> "patch"
-  in
+  let patch_cmd = Lazy.force patch_cmd in
   make_command ~name:"patch" ~dir patch_cmd ["-p1"; "-i"; p'] @@> fun r ->
     if not (OpamConsole.debug ()) then Sys.remove p';
     if OpamProcess.is_success r then Done None

src/core/opamSystem.mli

@@ -304,6 +304,8 @@ val get_lock_fd: lock -> Unix.file_descr
 
 (** {2 Misc} *)
 
+val is_gpatch_available : bool Lazy.t
+
 (** Apply a patch file in the current directory. If [preprocess] is set to
     false, there is no CRLF translation. Returns the error if the patch didn't
     apply. *)

src/repository/opamRepository.ml

@@ -530,6 +530,8 @@ let cleanup_repo_update upd =
 
 let update repo repo_root =
   log "update %a" (slog OpamRepositoryBackend.to_string) repo;
+  if not (Lazy.force OpamSystem.is_gpatch_available) then
+    OpamConsole.warning "Invalid patch utility. Please install GNU patch";
   let module B = (val find_backend repo: OpamRepositoryBackend.S) in
   B.fetch_repo_update repo.repo_name repo_root repo.repo_url @@+ function
   | Update_err e -> raise e

tests/reftests/repository.test

@@ -7,6 +7,7 @@ some content
 ### : Internal repository storage as archive or plain directory :
 ### opam switch create tarring --empty
 ### opam update -vv | grep '^\+' | sed-cmd diff | sed-cmd patch | 'patch-[^"]+' -> 'patch'
++ patch "--version"
 + diff "-ruaN" "default" "default.new" (CWD=${BASEDIR}/OPAM/repo)
 + patch "-p1" "-i" "${BASEDIR}/OPAM/log/patch" (CWD=${BASEDIR}/OPAM/repo/default)
 ### ls $OPAMROOT/repo | grep -v "cache"
@@ -25,6 +26,7 @@ build: ["test" "-f" "baz"]
 ### <REPO/packages/foo/foo.2/files/baz>
 some content
 ### opam update default -vv | grep '^\+' | sed-cmd tar | sed-cmd diff | sed-cmd patch | 'patch-[^"]+' -> 'patch'
++ patch "--version"
 + diff "-ruaN" "default" "default.new" (CWD=${BASEDIR}/OPAM/repo)
 + patch "-p1" "-i" "${BASEDIR}/OPAM/log/patch" (CWD=${BASEDIR}/OPAM/repo/default)
 + tar "cfz" "${BASEDIR}/OPAM/repo/default.tar.gz.tmp" "-C" "${BASEDIR}/OPAM/repo" "default"
@@ -63,6 +65,7 @@ build: ["test" "-f" "baz"]
 some content
 ### opam update -vv | grep '^\+' | sed-cmd tar | sed-cmd diff | sed-cmd patch | 'patch-[^"]+' -> 'patch'
 + tar "xfz" "${BASEDIR}/OPAM/repo/tarred.tar.gz" "-C" "${OPAMTMP}"
++ patch "--version"
 + diff "-ruaN" "tarred" "tarred.new" (CWD=${OPAMTMP})
 + patch "-p1" "-i" "${BASEDIR}/OPAM/log/patch" (CWD=${OPAMTMP}/tarred)
 + tar "cfz" "${BASEDIR}/OPAM/repo/tarred.tar.gz.tmp" "-C" "${OPAMTMP}" "tarred"
@@ -85,6 +88,7 @@ build: ["test" "-f" "quux"]
 some content
 ### opam update -vv | grep '^\+' | sed-cmd tar | sed-cmd diff | sed-cmd patch | 'patch-[^"]+' -> 'patch'
 + tar "xfz" "${BASEDIR}/OPAM/repo/tarred.tar.gz" "-C" "${OPAMTMP}"
++ patch "--version"
 + diff "-ruaN" "tarred" "tarred.new" (CWD=${OPAMTMP})
 + patch "-p1" "-i" "${BASEDIR}/OPAM/log/patch" (CWD=${OPAMTMP}/tarred)
 ### opam install foo.5 -vv | grep '^\+' | sed-cmd test