reftest: Add a test showing the output of opam update in verbose mode

tests/reftests/dune.inc

@@ -1436,6 +1436,24 @@
    %{targets}
    (run ./run.exe %{exe:../../src/client/opamMain.exe.exe} %{dep:update-upgrade.test} %{read-lines:testing-env}))))
 
+(rule
+ (alias reftest-update)
+ (action
+  (diff update.test update.out)))
+
+(alias
+ (name reftest)
+ (deps (alias reftest-update)))
+
+(rule
+ (targets update.out)
+ (deps root-N0REP0)
+ (package opam)
+ (action
+  (with-stdout-to
+   %{targets}
+   (run ./run.exe %{exe:../../src/client/opamMain.exe.exe} %{dep:update.test} %{read-lines:testing-env}))))
+
 (rule
  (alias reftest-upgrade-format)
  (action

tests/reftests/update.test

@@ -0,0 +1,9 @@
+N0REP0
+### <REPO/packages/pkg/pkg.1/opam>
+opam-version: "2.0"
+### opam update --verbose
+
+<><> Updating package repositories ><><><><><><><><><><><><><><><><><><><><><><>
+Processing  1/1: [default: rsync]
+[default] synchronised from file://${BASEDIR}/REPO
+Now run 'opam upgrade' to apply any package updates.