add check on pre-push stage: exit if staged files not committed yet

.gitignore

@@ -4,3 +4,4 @@
 /.tox
 /dist
 .vscode/
+.idea

pre_commit/commands/run.py

@@ -371,7 +371,14 @@ def run(
             environ.get('_PRE_COMMIT_SKIP_POST_CHECKOUT')
     ):
         return 0
-
+    # prevent pushing staged files not committed (#2486)
+    if (
+            args.hook_stage == 'pre-push' and git.get_staged_files()
+    ):
+        logger.error(
+            'Staged files found. Please commit before pushing',
+        )
+        return 1
     # Expose prepare_commit_message_source / commit_object_name
     # as environment variables for the hooks
     if args.prepare_commit_message_source:

tests/commands/run_test.py

@@ -1246,3 +1246,36 @@ def test_pre_commit_env_variable_set(cap_out, store, repo_with_passing_hook):
         cap_out, store, repo_with_passing_hook, args, environ,
     )
     assert environ['PRE_COMMIT'] == '1'
+
+
+def test_pre_push_fails_if_staged_files(
+        cap_out, store, repo_with_passing_hook,
+):
+    config = {
+        'repo': 'local',
+        'hooks': [{
+            'id': 'no-todo',
+            'name': 'No TODO',
+            'entry': 'sh -c "! grep -iI todo $@" --',
+            'language': 'system',
+            'stage': 'pre-push',
+        }],
+    }
+    add_config_to_repo(repo_with_passing_hook, config)
+
+    with open('placeholder.py', 'w') as staged_file:
+        staged_file.write('"""TODO: something"""\n')
+    cmd_output('git', 'add', 'placeholder.py')
+    git_commit()
+    with open('placeholder.py', 'w') as staged_file:
+        staged_file.write('"""Ok"""\n')
+
+    cmd_output('git', 'add', 'placeholder.py')
+
+    args = run_opts(hook_stage='pre-push')
+    ret, printed = _do_run(cap_out, store, repo_with_passing_hook, args)
+    assert ret == 1
+    assert printed == (
+        b'[ERROR] Staged files found.'
+        b' Please commit before pushing\n'
+    )