Add recipe support.

recipes/GitBranch/recipe.py

@@ -0,0 +1,26 @@
+
+from git import Repo
+from git.exc import GitError
+import hashlib
+import os
+from SCons.Script import *
+
+def cook(env: Environment, repo_name: str, remote_url: str, git_ref: str = "main") -> dict:
+    repo_dir = os.path.join(env['CLONE_DIR'], 'git', repo_name, '_bare')
+    try:
+        repo = Repo(repo_dir)
+        origin = repo.remotes['origin']
+    except GitError:
+        print(f'Initializing git repository for SDL at {repo_dir}.')
+        repo = Repo.init(repo_dir, bare=True)
+        origin = repo.create_remote('origin', remote_url)
+    worktree_dir = os.path.join(env['CLONE_DIR'], 'git', repo_name, hashlib.shake_128(git_ref.encode('utf-8')).hexdigest(6)) # TODO: commit hash would be better, right?
+    if not os.path.exists(worktree_dir):
+        print(f'Checking out into {worktree_dir}.')
+        origin.fetch()
+        os.makedirs(worktree_dir)
+        repo.git.worktree('add', worktree_dir, git_ref)
+    return {
+        'checkout_root': worktree_dir
+    }
+