Ignore .osc directory

Reviewed-on: importers/git-importer#26
Reviewed-by: Dirk Mueller <dirkmueller@noreply@src.opensuse.org>

lib/git.py

@@ -85,7 +85,7 @@ class Git:
         """Checkout into the branch HEAD"""
         new_branch = False
         if branch not in self.branches():
-            self.git_run(["branch", "-q", branch, "HEAD"])
+            self.git_run(["switch", "-q", "--orphan", branch])
             new_branch = True
         else:
             ref = f"refs/heads/{branch}"
@@ -182,6 +182,12 @@ class Git:
     def add(self, filename):
         self.git_run(["add", filename])
 
+    def add_default_gitignore(self):
+        if not (self.path / ".gitignore").exists():
+            with (self.path / ".gitignore").open("w") as f:
+                f.write(".osc\n")
+            self.add(".gitignore")
+
     def add_default_lfs_gitattributes(self, force=False):
         if not (self.path / ".gitattributes").exists() or force:
             with (self.path / ".gitattributes").open("w") as f:

lib/git_exporter.py

@@ -150,6 +150,7 @@ class GitExporter:
 
         # create file if not existant
         self.git.add_default_lfs_gitattributes(force=False)
+        self.git.add_default_gitignore()
 
         to_download, to_delete = flat.commit.calc_delta(branch_state[flat.branch])
         for file in to_delete: