Add some failing tests to the alias field

Signed-off-by: Rudi Grinberg <rudi.grinberg@gmail.com>

test/blackbox-tests/dune.inc

@@ -853,6 +853,14 @@
    test-cases/github2629
    (progn (run %{exe:cram.exe} -test run.t) (diff? run.t run.t.corrected)))))
 
+(alias
+ (name github2681)
+ (deps (package dune) (source_tree test-cases/github2681))
+ (action
+  (chdir
+   test-cases/github2681
+   (progn (run %{exe:cram.exe} -test run.t) (diff? run.t run.t.corrected)))))
+
 (alias
  (name github534)
  (deps (package dune) (source_tree test-cases/github534))
@@ -1950,6 +1958,7 @@
   (alias github25)
   (alias github2584)
   (alias github2629)
+  (alias github2681)
   (alias github534)
   (alias github568)
   (alias github597)
@@ -2166,6 +2175,7 @@
   (alias github25)
   (alias github2584)
   (alias github2629)
+  (alias github2681)
   (alias github534)
   (alias github568)
   (alias github597)

test/blackbox-tests/test-cases/github2681/run.t

@@ -0,0 +1,37 @@
+A rule may have an alias field. This denotes that the action of the rule is a
+dependency of the alias.
+  $ mkdir simple && cd simple
+  $ cat > dune-project <<EOF
+  > (lang dune 2.0)
+  > EOF
+  $ cat > dune <<EOF
+  > (rule
+  >  (action (with-stdout-to foo (echo "hello world")))
+  >  (alias bar))
+  > EOF
+  $ dune build @bar --display short
+  File "dune", line 2, characters 9-50:
+  2 |  (action (with-stdout-to foo (echo "hello world")))
+               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  Error: Rule has targets in different directories.
+  Targets:
+  - _build/.aliases/default/bar-fc3cef760337ee5dd7a56722c8e58053
+  - _build/default/foo
+  [1]
+
+The field order should not affect the alias field:
+  $ cd .. && mkdir field-order && cd field-order
+  $ cat > dune-project <<EOF
+  > (lang dune 2.0)
+  > EOF
+  $ cat > dune <<EOF
+  > (rule
+  >  (alias bar)
+  >  (action (with-stdout-to foo (echo "hello world"))))
+  > EOF
+  $ dune build
+  File "dune", line 2, characters 2-7:
+  2 |  (alias bar)
+        ^^^^^
+  Error: Unknown action or rule field.
+  [1]