unikernel/duniverse/dune_/test/blackbox-tests/test-cases/promote/promote-only-when-needed.t

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+Test that targets aren't re-promoted if they are up to date.
+
+  $ echo "(lang dune 3.0)" > dune-project
+  $ cat >dune <<EOF
+  > (rule
+  >  (targets promoted)
+  >  (mode promote)
+  >  (action (with-stdout-to promoted (echo "Hello, world!"))))
+  > EOF
+
+  $ dune build promoted --verbose 2>&1 | grep "Promoting"
+  Promoting "_build/default/promoted" to "promoted"
+  $ cat promoted
+  Hello, world!
+
+Dune doesn't promote the file again if it's unchanged.
+
+  $ dune build promoted --verbose 2>&1 | grep "Promoting"
+  [1]
+  $ cat promoted
+  Hello, world!
+
+Dune does promotes the file again if it's changed.
+
+  $ echo hi > promoted
+  $ dune build promoted --verbose 2>&1 | grep "Promoting"
+  Promoting "_build/default/promoted" to "promoted"
+  $ cat promoted
+  Hello, world!
+
+Now test behaviour for executables, which use artifact substitution.
+
+  $ git init --quiet
+
+  $ cat >dune <<EOF
+  > (executable
+  >  (name hello)
+  >  (libraries dune-build-info)
+  >  (promote))
+  > EOF
+
+  $ cat >hello.ml <<EOF
+  > print_endline "Hello, World!";
+  > (match Build_info.V1.version () with
+  >   | Some _ -> print_endline "Has version info"
+  >   | None -> print_endline "Has no version info")
+  > EOF
+
+  $ dune build hello.exe --verbose 2>&1 | grep "Promoting"
+  Promoting "_build/default/hello.exe" to "hello.exe"
+  $ ./hello.exe
+  Hello, World!
+  Has version info
+
+Bug: Dune currently re-promotes versioned executables on every restart.
+
+# CR-someday amokhov: Fix this.
+
+  $ dune build hello.exe --verbose 2>&1 | grep "Promoting"
+  Promoting "_build/default/hello.exe" to "hello.exe"