Implement --prefix option

It is advertised already, and TopicManager is ready for it too. Wire it
all together.

Fixes aspiers#8

git_explode/cli.py

@@ -35,9 +35,10 @@ def parse_args(args):
     parser.add_argument(
         '-p', '--prefix',
         dest="prefix",
-        help="prefix for all created topic branches",
+        help="prefix for all created topic branches [%(default)]",
         type=str,
-        metavar="PREFIX")
+        metavar="PREFIX",
+        default="topic")
     parser.add_argument(
         '-c', '--context-lines',
         dest='context_lines',
@@ -63,7 +64,7 @@ def main(args):
     args = parse_args(args)
     repo = GitUtils.get_repo()
     exploder = GitExploder(repo, args.base, args.head, args.debug,
-                           args.context_lines)
+                           args.context_lines, args.prefix)
     exploder.run()
 
 

git_explode/exploder.py

@@ -18,7 +18,7 @@ class GitExploder(object):
     topic branches.
 
     """
-    def __init__(self, repo, base, head, debug, context_lines):
+    def __init__(self, repo, base, head, debug, context_lines, prefix):
         self.logger = standard_logger('git-explode', debug)
 
         self.debug = debug
@@ -29,7 +29,7 @@ def __init__(self, repo, base, head, debug, context_lines):
                           (base, GitUtils.commit_summary(self.base_commit)))
         self.head = head
         self.context_lines = context_lines
-        self.topic_mgr = TopicManager('topic%d', self.logger)
+        self.topic_mgr = TopicManager('%s%%d' % prefix, self.logger)
 
         # Map commits to their exploded version
         self.exploded = {}