external repo: checkout rev before initializing repo

dvc/external_repo.py

@@ -61,11 +61,12 @@ def _external_repo(url=None, rev=None, cache_dir=None):
         REPO_CACHE[url, None, None] = clean_clone_path
 
     # Adjust new clone/copy to fit rev and cache_dir
+
+    # Checkout first in case of non dvc master
+    checkout_revision(new_path, rev)
+
     repo = Repo(new_path)
     try:
-        if rev is not None:
-            repo.scm.checkout(rev)
-
         if cache_dir is not None:
             cache_config = CacheConfig(repo.config)
             cache_config.set_dir(cache_dir, level=Config.LEVEL_LOCAL)
@@ -77,6 +78,14 @@ def _external_repo(url=None, rev=None, cache_dir=None):
     return new_path
 
 
+def checkout_revision(repo_path, revision):
+    if revision is not None:
+        from dvc.scm import Git
+
+        git = Git(repo_path)
+        git.checkout(revision)
+
+
 def clean_repos():
     # Outside code should not see cache while we are removing
     repo_paths = list(REPO_CACHE.values())

tests/func/test_get.py

@@ -8,6 +8,7 @@ import pytest
 from dvc.config import Config
 from dvc.exceptions import GetDVCFileError
 from dvc.exceptions import UrlNotDvcRepoError
+from dvc.remote import RemoteConfig
 from dvc.repo import Repo
 from dvc.system import System
 from dvc.utils import makedirs
@@ -87,3 +88,33 @@ def test_get_to_dir(dname, erepo):
 
     assert os.path.isdir(dname)
     assert filecmp.cmp(erepo.FOO, dst, shallow=False)
+
+
+@pytest.fixture
+def erepo_no_dvc_master(git_erepo):
+    dvc_branch = "dvc_test"
+    git_erepo.git.git.checkout("master", b=dvc_branch)
+    git_erepo.dvc_branch = dvc_branch
+
+    dvc_repo = Repo.init(git_erepo._root_dir)
+    stage, = dvc_repo.add([git_erepo.FOO])
+    dvc_repo.scm.add([".dvc", stage.relpath])
+
+    rconfig = RemoteConfig(dvc_repo.config)
+    rconfig.add("upstream", dvc_repo.cache.local.cache_dir, default=True)
+    dvc_repo.scm.add([dvc_repo.config.config_file])
+
+    dvc_repo.scm.commit("dvc branch initial")
+
+    git_erepo.git.git.checkout("master")
+    os.chdir(git_erepo._saved_dir)
+    yield git_erepo
+
+
+def test_get_from_non_dvc_master(empty_dir, erepo_no_dvc_master):
+    Repo.get(
+        erepo_no_dvc_master._root_dir,
+        "foo",
+        out="foo",
+        rev=erepo_no_dvc_master.dvc_branch,
+    )