exp run: Support --message.

Custom commit message to use when committing the experiment.

Part of #8870

tests/func/experiments/test_experiments.py

@@ -773,3 +773,19 @@ def test_mixed_git_dvc_out(tmp_dir, scm, dvc, exp_stage):
     assert (tmp_dir / "dir" / "metrics.yaml").exists()
     git_fs = scm.get_fs(exp)
     assert not git_fs.exists("dir/metrics.yaml")
+
+
+@pytest.mark.parametrize("tmp", [True, False])
+def test_custom_commit_message(tmp_dir, scm, dvc, tmp):
+    stage = dvc.stage.add(
+        cmd="echo foo",
+        name="foo",
+    )
+    scm.add_commit(["dvc.yaml"], message="add dvc.yaml")
+
+    exp = first(
+        dvc.experiments.run(
+            stage.addressing, tmp_dir=tmp, message="custom commit message"
+        )
+    )
+    assert scm.gitpython.repo.commit(exp).message == "custom commit message"

tests/func/experiments/test_queue.py

@@ -69,3 +69,16 @@ def test_copy_paths_queue(tmp_dir, scm, dvc):
     fs = scm.get_fs(exp)
     assert not fs.exists("dir")
     assert not fs.exists("file")
+
+
+def test_custom_commit_message_queue(tmp_dir, scm, dvc):
+    stage = dvc.stage.add(
+        cmd="echo foo",
+        name="foo",
+    )
+    scm.add_commit(["dvc.yaml"], message="add dvc.yaml")
+
+    dvc.experiments.run(stage.addressing, queue=True, message="custom commit message")
+
+    exp = first(dvc.experiments.run(run_all=True))
+    assert scm.gitpython.repo.commit(exp).message == "custom commit message"

tests/func/experiments/test_set_params.py

@@ -116,7 +116,12 @@ def test_hydra_sweep(
     assert patched.call_count == len(expected)
     for e in expected:
         patched.assert_any_call(
-            mocker.ANY, params=e, reset=True, targets=None, copy_paths=None
+            mocker.ANY,
+            params=e,
+            reset=True,
+            targets=None,
+            copy_paths=None,
+            message=None,
         )
 
 

tests/unit/command/test_experiments.py

@@ -136,6 +136,7 @@ def test_experiments_run(dvc, scm, mocker):
         "reset": False,
         "machine": None,
         "copy_paths": [],
+        "message": None,
     }
     default_arguments.update(repro_arguments)