Create new .ugit directory

how_to/Change_03.md

@@ -0,0 +1,18 @@
+- init: Create new .ugit directory
+
+The 'ugit init' command creates a new empty repository.
+
+Git stores all repository data locally, in a subdirectory called ".git", so upon
+initialization we'll create one.
+
+I named the directory ".ugit" rather than ".git" so that it doesn't clash with
+Git, but the idea is the same.
+
+To implement 'init', we could have just called os.makedirs from cli.py, but I
+want to have some separation between different logical parts of the code:
+
+   + cli.py - In charge of parsing and processing user input.
+   + data.py - Manages the data in .ugit directory. Here will be the code that
+   actually touches files on disk.
+
+This separation will be useful as the code will get larger.

ugit/cli.py

@@ -1,4 +1,7 @@
 import argparse
+from pathlib import Path
+
+from . import data
 
 
 def main():
@@ -19,4 +22,5 @@ def parse_args():
 
 
 def init(args):
-    print("Hello, World!")
+    data.init()
+    print(f"Initialized empty ugit repository in {Path.cwd()}/{data.GIT_DIR}")

ugit/data.py

@@ -0,0 +1,7 @@
+from pathlib import Path
+
+GIT_DIR = ".ugit"
+
+
+def init():
+    Path.mkdir(GIT_DIR)