command/new: make readme format configurable

This change makes readme formant configurable, defaulting to markdown
when using the new command.

Resolves: #280
Closes: #1515

Co-authored-by: Arun Babu Neelicattu <arun.neelicattu@gmail.com>

docs/docs/cli.md

@@ -31,7 +31,7 @@ will create a folder as follows:
 ```text
 my-package
 ├── pyproject.toml
-├── README.rst
+├── README.md
 ├── my_package
 │   └── __init__.py
 └── tests
@@ -56,7 +56,7 @@ That will create a folder structure as follows:
 ```text
 my-package
 ├── pyproject.toml
-├── README.rst
+├── README.md
 ├── src
 │   └── my_package
 │       └── __init__.py
@@ -76,6 +76,7 @@ will create the following structure:
 ```text
 my-package
 ├── pyproject.toml
+├── README.md
 ├── src
 │   └── my
 │       └── package

poetry/console/commands/new.py

@@ -15,6 +15,12 @@ class NewCommand(Command):
     options = [
         option("name", None, "Set the resulting package name.", flag=False),
         option("src", None, "Use the src layout for the project."),
+        option(
+            "readme",
+            None,
+            "Specify the readme file format. One of md (default) or rst",
+            flag=False,
+        ),
     ]
 
     def handle(self) -> None:
@@ -46,7 +52,7 @@ class NewCommand(Command):
                     "exists and is not empty".format(path)
                 )
 
-        readme_format = "rst"
+        readme_format = self.option("readme") or "md"
 
         config = GitConfig()
         author = None

tests/console/commands/test_new.py

-import pytest
+from pathlib import Path
+from typing import Optional
 
-from cleo.testers import CommandTester
+import pytest
 
-from poetry.console import Application
 from poetry.factory import Factory
 from poetry.poetry import Poetry
-from poetry.utils._compat import Path  # noqa
 
 
 @pytest.fixture
-def command(app, poetry):  # type: (Application, Poetry) -> CommandTester
-    command = app.find("new")
-    command._pool = poetry.pool
-    return CommandTester(command)
+def tester(command_tester_factory):
+    return command_tester_factory("new")
 
 
-def verify_project_directory(path, package_name, package_path, include_from=None):
+def verify_project_directory(
+    path: Path, package_name: str, package_path: str, include_from: Optional[str] = None
+) -> Poetry:
     package_path = Path(package_path)
     assert path.is_dir()
 
@@ -47,6 +46,8 @@ def verify_project_directory(path, package_name, package_path, include_from=None
         assert len(packages) == 1
         assert packages[0] == package_include
 
+    return poetry
+
 
 @pytest.mark.parametrize(
     "options,directory,package_name,package_path,include_from",
@@ -134,9 +135,21 @@ def verify_project_directory(path, package_name, package_path, include_from=None
     ],
 )
 def test_command_new(
-    options, directory, package_name, package_path, include_from, command, tmp_dir
+    options, directory, package_name, package_path, include_from, tester, tmp_dir
 ):
     path = Path(tmp_dir) / directory
     options.append(path.as_posix())
-    command.execute(" ".join(options))
+    tester.execute(" ".join(options))
     verify_project_directory(path, package_name, package_path, include_from)
+
+
+@pytest.mark.parametrize("fmt", [(None,), ("md",), ("rst",)])
+def test_command_new_with_readme(fmt, tester, tmp_dir):
+    fmt = "md"
+    package = "package"
+    path = Path(tmp_dir) / package
+    options = ["--readme {}".format(fmt) if fmt else "md", path.as_posix()]
+    tester.execute(" ".join(options))
+
+    poetry = verify_project_directory(path, package, package, None)
+    assert poetry.local_config.get("readme") == "README.{}".format(fmt or "md")