Merge ~mitya57/git-build-recipe:master into git-build-recipe:master

[Dmitry Shachnev]

Make pull_or_clone work when the target dir exists and is empty. This allows one to use the nest command as a replacement for submodules.

Add two new tests for pull_or_clone function: one when the target directory is empty, and another one when it contains a subdirectory.

Fixes LP: #1644640.

[Alberts Muktupāvels (muktupavels)]

review: Approve

[Colin Watson (cjwatson)]

review: Approve

diff --git a/gitbuildrecipe/recipe.py b/gitbuildrecipe/recipe.py
index 3275775..d1700f2 100644
--- a/gitbuildrecipe/recipe.py
+++ b/gitbuildrecipe/recipe.py
@@ -295,6 +295,8 @@ insteadof = {
 def pull_or_clone(base_branch, target_path):
     """Make target_path match base_branch, either by pulling or by cloning."""
     base_branch.path = target_path
+    if os.path.exists(target_path) and not os.listdir(target_path):
+        os.rmdir(target_path)
     if not os.path.exists(target_path):
         os.makedirs(target_path)
         base_branch.git_call("init")
diff --git a/gitbuildrecipe/tests/test_recipe.py b/gitbuildrecipe/tests/test_recipe.py
index c3c8491..ed7634d 100644
--- a/gitbuildrecipe/tests/test_recipe.py
+++ b/gitbuildrecipe/tests/test_recipe.py
@@ -543,7 +543,7 @@ class BuildTreeTests(GitTestCase):
         source = GitRepository("source")
         source.commit("one")
         # We just create the target as a directory
-        os.mkdir("target")
+        os.makedirs("target/junk")
         base_branch = BaseRecipeBranch("source", "1", 0.2)
         self.assertRaises(
             TargetAlreadyExists, build_tree, base_branch, "target")
@@ -867,6 +867,30 @@ class BuildTreeTests(GitTestCase):
         self.assertEqual(first_commit, target.rev_parse("one"))
         self.assertEqual(["?? b"], target.status())
 
+    def test_pull_or_clone_branch_target_is_empty_dir(self):
+        source = GitRepository("source")
+        source.build_tree(["a"])
+        source.add(["a"])
+        commit = source.commit("one")
+        source.tag("one", commit)
+        base_branch = BaseRecipeBranch("source", "1", 0.2, revspec=commit)
+        os.mkdir("target")
+        pull_or_clone(base_branch, "target")
+        target = GitRepository("target", allow_create=False)
+        self.assertEqual(commit, target.last_revision())
+        self.assertEqual(commit, target.rev_parse("one"))
+
+    def test_pull_or_clone_branch_target_is_nonempty_dir(self):
+        source = GitRepository("source")
+        source.build_tree(["a"])
+        source.add(["a"])
+        commit = source.commit("one")
+        source.tag("one", commit)
+        base_branch = BaseRecipeBranch("source", "1", 0.2, revspec=commit)
+        os.makedirs("target/junk")
+        self.assertRaises(
+            TargetAlreadyExists, pull_or_clone, base_branch, "target")
+
     def test_build_tree_runs_commands(self):
         source = GitRepository("source")
         commit = source.commit("one")