diff --git a/git_command.py b/git_command.py
index 513b9eb..d1e0c97 100644
--- a/git_command.py
+++ b/git_command.py
@@ -72,6 +72,8 @@
       pass
   _ssh_clients = []
 
+_git_version = None
+
 class _GitCall(object):
   def version(self):
     p = GitCommand(None, ['--version'], capture_stdout=True)
@@ -79,6 +81,21 @@
       return p.stdout
     return None
 
+  def version_tuple(self):
+    global _git_version
+
+    if _git_version is None:
+      ver_str = git.version()
+      if ver_str.startswith('git version '):
+        _git_version = tuple(
+          map(lambda x: int(x),
+            ver_str[len('git version '):].strip().split('.')[0:3]
+          ))
+      else:
+        print >>sys.stderr, 'fatal: "%s" unsupported' % ver_str
+        sys.exit(1)
+    return _git_version
+
   def __getattr__(self, name):
     name = name.replace('_','-')
     def fun(*cmdv):
@@ -88,23 +105,9 @@
     return fun
 git = _GitCall()
 
-_git_version = None
-
 def git_require(min_version, fail=False):
-  global _git_version
-
-  if _git_version is None:
-    ver_str = git.version()
-    if ver_str.startswith('git version '):
-      _git_version = tuple(
-        map(lambda x: int(x),
-          ver_str[len('git version '):].strip().split('.')[0:3]
-        ))
-    else:
-      print >>sys.stderr, 'fatal: "%s" unsupported' % ver_str
-      sys.exit(1)
-
-  if min_version <= _git_version:
+  git_version = git.version_tuple()
+  if min_version <= git_version:
     return True
   if fail:
     need = '.'.join(map(lambda x: str(x), min_version))
diff --git a/main.py b/main.py
index 48edc1c..9c545b3 100755
--- a/main.py
+++ b/main.py
@@ -29,6 +29,7 @@
 import urllib2
 
 from trace import SetTrace
+from git_command import git, GitCommand
 from git_config import init_ssh, close_ssh
 from command import InteractiveCommand
 from command import MirrorSafeCommand
@@ -134,6 +135,9 @@
         print >>sys.stderr, 'error: no project in current directory'
       sys.exit(1)
 
+def _MyRepoPath():
+  return os.path.dirname(__file__)
+
 def _MyWrapperPath():
   return os.path.join(os.path.dirname(__file__), 'repo')
 
@@ -200,11 +204,63 @@
       continue
     i += 1
 
+_user_agent = None
+
+def _UserAgent():
+  global _user_agent
+
+  if _user_agent is None:
+    py_version = sys.version_info
+
+    os_name = sys.platform
+    if os_name == 'linux2':
+      os_name = 'Linux'
+    elif os_name == 'win32':
+      os_name = 'Win32'
+    elif os_name == 'cygwin':
+      os_name = 'Cygwin'
+    elif os_name == 'darwin':
+      os_name = 'Darwin'
+
+    p = GitCommand(
+      None, ['describe', 'HEAD'],
+      cwd = _MyRepoPath(),
+      capture_stdout = True)
+    if p.Wait() == 0:
+      repo_version = p.stdout
+      if len(repo_version) > 0 and repo_version[-1] == '\n':
+        repo_version = repo_version[0:-1]
+      if len(repo_version) > 0 and repo_version[0] == 'v':
+        repo_version = repo_version[1:]
+    else:
+      repo_version = 'unknown'
+
+    _user_agent = 'git-repo/%s (%s) git/%s Python/%d.%d.%d' % (
+      repo_version,
+      os_name,
+      '.'.join(map(lambda d: str(d), git.version_tuple())),
+      py_version[0], py_version[1], py_version[2])
+  return _user_agent
+
+class _UserAgentHandler(urllib2.BaseHandler):
+  def http_request(self, req):
+    req.add_header('User-Agent', _UserAgent())
+    return req
+
+  def https_request(self, req):
+    req.add_header('User-Agent', _UserAgent())
+    return req
+
 def init_http():
+  handlers = [_UserAgentHandler()]
+
   if 'http_proxy' in os.environ:
     url = os.environ['http_proxy']
-    proxy_support = urllib2.ProxyHandler({'http': url, 'https': url})
-    urllib2.install_opener(urllib2.build_opener(proxy_support))
+    handlers.append(urllib2.ProxyHandler({'http': url, 'https': url}))
+  if 'REPO_CURL_VERBOSE' in os.environ:
+    handlers.append(urllib2.HTTPHandler(debuglevel=1))
+    handlers.append(urllib2.HTTPSHandler(debuglevel=1))
+  urllib2.install_opener(urllib2.build_opener(*handlers))
 
 def _Main(argv):
   opt = optparse.OptionParser(usage="repo wrapperinfo -- ...")