scm: split tracking of to-be git-ignored/git-staged into SCMContext

tests/func/test_scm_context.py

@@ -0,0 +1,62 @@
+def test_scm_context_autostage(tmp_dir, scm, dvc):
+    tmp_dir.gen("foo", "foo")
+    with dvc.scm_context(autostage=True) as context:
+        context.track_file("foo")
+
+    scm._reset()
+    assert scm.is_tracked("foo")
+
+
+def test_scm_context_ignore(tmp_dir, scm, dvc):
+    with dvc.scm_context as context:
+        context.ignore(tmp_dir / "foo")
+        assert context.files_to_track == {scm.GITIGNORE}
+
+    scm._reset()
+    assert scm.is_ignored("foo")
+
+
+def test_scm_context_when_already_ignored(tmp_dir, scm, dvc):
+    scm.ignore(tmp_dir / "foo")
+    scm._reset()
+
+    with dvc.scm_context() as context:
+        context.ignore(tmp_dir / "foo")
+        # If files are already ignored, dvc should not try to track a new
+        # .gitignore file as it's a no-op.
+        assert not context.files_to_track
+
+    scm._reset()
+    assert scm.is_ignored("foo")
+
+
+def test_scm_context_ignore_remove(tmp_dir, scm, dvc):
+    scm.ignore(tmp_dir / "foo")
+    scm.ignore(tmp_dir / "bar")
+
+    with dvc.scm_context:
+        dvc.scm_context.ignore_remove(tmp_dir / "foo")
+        assert dvc.scm_context.files_to_track == {scm.GITIGNORE}
+
+    scm._reset()
+    assert not scm.is_ignored("foo")
+
+
+def test_scm_context_try_ignore_remove_non_existing_entry(tmp_dir, dvc, scm):
+    with dvc.scm_context as context:
+        context.ignore_remove(tmp_dir / "foo")
+        assert not context.files_to_track
+    scm._reset()
+    assert not scm.is_ignored("foo")
+
+
+def test_scm_context_no_track_on_ignore_remove(tmp_dir, dvc, scm):
+    # DVC should not keep track of file when nothing actually changed
+    # i.e. here ignore was reverted back.
+    scm.ignore(tmp_dir / "foo")
+    with dvc.scm_context:
+        dvc.scm_context.ignore_remove(tmp_dir / "foo")
+        assert not dvc.scm_context.files_to_track
+
+    scm._reset()
+    assert not scm.is_ignored("foo")