exp: Update --rev to support append action.

Closes #9390

dvc/commands/experiments/__init__.py

@@ -82,6 +82,7 @@ def add_rev_selection_flags(
     experiments_subcmd_parser.add_argument(
         "--rev",
         type=str,
+        action="append",
         default=None,
         help=msg,
         metavar="<commit>",

tests/unit/command/test_experiments.py

@@ -116,7 +116,7 @@ def test_experiments_show(dvc, scm, mocker):
         hide_queued=True,
         hide_failed=True,
         num=1,
-        revs="foo",
+        revs=["foo"],
         sha_only=True,
         param_deps=True,
         fetch_running=True,
@@ -226,7 +226,7 @@ def test_experiments_list(dvc, scm, mocker):
     m.assert_called_once_with(
         cmd.repo,
         git_remote="origin",
-        rev="foo",
+        rev=["foo"],
         all_commits=True,
         num=-1,
     )
@@ -265,7 +265,7 @@ def test_experiments_push(dvc, scm, mocker):
         cmd.repo,
         "origin",
         ["experiment1", "experiment2"],
-        rev="foo",
+        rev=["foo"],
         all_commits=True,
         num=2,
         force=True,
@@ -322,7 +322,7 @@ def test_experiments_pull(dvc, scm, mocker):
         cmd.repo,
         "origin",
         ["experiment"],
-        rev="foo",
+        rev=["foo"],
         all_commits=True,
         num=1,
         force=True,
@@ -371,7 +371,7 @@ def test_experiments_remove_flag(dvc, scm, mocker, capsys, caplog):
         cmd.repo,
         exp_names=[],
         all_commits=True,
-        rev="foo",
+        rev=["foo"],
         num=2,
         queue=False,
         git_remote="myremote",