dvc: more explict error during init when .dvc is ignored by git (#4978)

* dvc: more explict error during init when .dvc is ignored by git

Fixes #3738

* dvc: address PR feedback

* styling

* styling

.gitignore

@@ -5,6 +5,7 @@ neatlynx/__pycache__
 *.pyc
 .env/
 .env2.7/
+.python-version
 
 .dvc.conf.lock
 .DS_Store

dvc/repo/init.py

@@ -45,19 +45,22 @@ def init(root_dir=os.curdir, no_scm=False, force=False, subdir=False):
         scm = SCM(root_dir, search_parent_directories=subdir, no_scm=no_scm)
     except SCMError:
         raise InitError(
-            "{repo} is not tracked by any supported SCM tool (e.g. Git). "
+            f"{root_dir} is not tracked by any supported SCM tool (e.g. Git). "
             "Use `--no-scm` if you don't want to use any SCM or "
             "`--subdir` if initializing inside a subdirectory of a parent SCM "
-            "repository.".format(repo=root_dir)
+            "repository."
+        )
+
+    if scm.is_ignored(dvc_dir):
+        raise InitError(
+            f"{dvc_dir} is ignored by your SCM tool. \n"
+            "Make sure that it's tracked, "
+            "for example, by adding '!.dvc' to .gitignore."
         )
 
     if os.path.isdir(dvc_dir):
         if not force:
-            raise InitError(
-                "'{repo}' exists. Use `-f` to force.".format(
-                    repo=relpath(dvc_dir)
-                )
-            )
+            raise InitError(f"'{relpath(dvc_dir)}' exists. Use `-f` to force.")
 
         remove(dvc_dir)
 

dvc/scm/base.py

@@ -66,6 +66,10 @@ class Base:
         """
         return True
 
+    def is_ignored(self, path):  # pylint: disable=unused-argument
+        """Returns whether or not path is ignored by SCM."""
+        return False
+
     def ignore(self, path):  # pylint: disable=unused-argument
         """Makes SCM ignore a specified path."""
 

dvc/scm/git.py

@@ -183,7 +183,7 @@ class Git(Base):
 
         return entry, gitignore
 
-    def _ignored(self, path):
+    def is_ignored(self, path):
         from dulwich import ignore
         from dulwich.repo import Repo
 
@@ -194,7 +194,7 @@ class Git(Base):
     def ignore(self, path):
         entry, gitignore = self._get_gitignore(path)
 
-        if self._ignored(path):
+        if self.is_ignored(path):
             return
 
         msg = "Adding '{}' to '{}'.".format(relpath(path), relpath(gitignore))

tests/func/test_init.py

@@ -111,3 +111,17 @@ def test_gen_dvcignore(tmp_dir):
         "# https://dvc.org/doc/user-guide/dvcignore\n"
     )
     assert text == (tmp_dir / ".dvcignore").read_text()
+
+
+def test_init_when_ignored_by_git(tmp_dir, scm, caplog):
+    # https://github.com/iterative/dvc/issues/3738
+    tmp_dir.gen({".gitignore": ".*"})
+    with caplog.at_level(logging.ERROR, logger="dvc"):
+        assert main(["init"]) == 1
+    assert (
+        "{dvc_dir} is ignored by your SCM tool. \n"
+        "Make sure that it's tracked, "
+        "for example, by adding '!.dvc' to .gitignore.".format(
+            dvc_dir=tmp_dir / DvcRepo.DVC_DIR
+        )
+    ) in caplog.text

tests/func/test_scm.py

@@ -92,8 +92,8 @@ def test_ignored(tmp_dir, scm):
     tmp_dir.gen({"dir1": {"file1.jpg": "cont", "file2.txt": "cont"}})
     tmp_dir.gen({".gitignore": "dir1/*.jpg"})
 
-    assert scm._ignored(os.fspath(tmp_dir / "dir1" / "file1.jpg"))
-    assert not scm._ignored(os.fspath(tmp_dir / "dir1" / "file2.txt"))
+    assert scm.is_ignored(tmp_dir / "dir1" / "file1.jpg")
+    assert not scm.is_ignored(tmp_dir / "dir1" / "file2.txt")
 
 
 def test_get_gitignore(tmp_dir, scm):