Delete the merge branch if merge successful

Also give some better error messages and docs

Author: coretl

README.rst

@@ -22,10 +22,12 @@ It integrates the following tools:
 - Pytest for code and coverage
 - Sphinx for tutorials, how-to guides, explanations and reference documentation
 - GitHub Actions for code and docs CI and deployment to PyPI and GitHub Pages
-- VSCode settings using black, flake8, isort and mypy on save
+- If you use VSCode, it will run black, flake8, isort and mypy on save
 
 The ``skeleton`` branch of this module contains the source code that can be
 merged into new or existing projects, and pulled from to keep them up to date.
+It can also serve as a working example for those who would prefer to
+cherry-pick.
 
 The ``master`` branch contains the
 docs and a command line tool to ease the adoption of this skeleton into new::

src/dls_python3_skeleton/__main__.py

@@ -95,12 +95,19 @@ def merge_skeleton(
         # The merge failed, so ask the user to fix it
         print("Please fix the conflicts above, then you can run:")
         print(f"    git branch -d {MERGE_BRANCH}")
+    else:
+        git("branch", "-d", MERGE_BRANCH, cwd=path)
     print("Instructions on how to develop this module are in CONTRIBUTING.rst")
 
 
 def new(args):
     path: Path = args.path
-    path.mkdir(parents=True)
+    if path.exists():
+        assert path.is_dir() and not list(
+            path.iterdir()
+        ), f"Expected {path} to not exist, or be an empty dir"
+    else:
+        path.mkdir(parents=True)
     git("init", cwd=path)
     print(f"Created git repo in {path}")
     merge_skeleton(
@@ -114,6 +121,7 @@ def new(args):
 
 def existing(args):
     path: Path = args.path
+    assert path.is_dir(), f"Expected {path} to be an existing directory"
     conf = ConfigParser()
     conf.read(path / "setup.cfg")
     merge_skeleton(

tests/test_dls_python3_skeleton.py

@@ -43,6 +43,7 @@ def test_new_module(tmp_path: Path):
     assert conf["metadata"]["author"] == "Firstname Lastname"
     assert conf["metadata"]["author_email"] == "[email protected]"
     assert (module / "src" / "my_module").is_dir()
+    assert check_output("git", "branch", cwd=module).strip() == "* master"
     check_output("pipenv", "install", "--dev", cwd=module)
     check_output("pipenv", "run", "docs", cwd=module)
     with pytest.raises(ValueError) as ctx: