--- a/mercurial/hook.py
+++ b/mercurial/hook.py
@@ -98,7 +98,10 @@
         cwd = repo.root
     else:
         cwd = os.getcwd()
-    r = util.system(cmd, environ=env, cwd=cwd)
+    if 'HG_URL' in env and env['HG_URL'].startswith('remote:http'):
+        r = util.system(cmd, environ=env, cwd=cwd, out=ui)
+    else:
+        r = util.system(cmd, environ=env, cwd=cwd)
     if r:
         desc, r = util.explain_exit(r)
         if throw:

--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -366,13 +366,16 @@
     global _hgexecutable
     _hgexecutable = path
 
-def system(cmd, environ={}, cwd=None, onerr=None, errprefix=None):
+def system(cmd, environ={}, cwd=None, onerr=None, errprefix=None, out=None):
     '''enhanced shell command execution.
     run with environment maybe modified, maybe in different dir.
 
     if command fails and onerr is None, return status.  if ui object,
     print error message and return status, else raise onerr object as
-    exception.'''
+    exception.
+
+    if out is specified, it is assumed to be a file-like object that has a
+    write() method. stdout and stderr will be redirected to out.'''
     def py2shell(val):
         'convert python object into string that is useful to shell'
         if val is None or val is False:
@@ -386,8 +389,17 @@
     env = dict(os.environ)
     env.update((k, py2shell(v)) for k, v in environ.iteritems())
     env['HG'] = hgexecutable()
-    rc = subprocess.call(cmd, shell=True, close_fds=closefds,
-                         env=env, cwd=cwd)
+    if out is None:
+        rc = subprocess.call(cmd, shell=True, close_fds=closefds,
+                             env=env, cwd=cwd)
+    else:
+        proc = subprocess.Popen(cmd, shell=True, close_fds=closefds,
+                                env=env, cwd=cwd, stdout=subprocess.PIPE,
+                                stderr=subprocess.STDOUT)
+        for line in proc.stdout:
+            out.write(line)
+        proc.wait()
+        rc = proc.returncode
     if sys.platform == 'OpenVMS' and rc & 1:
         rc = 0
     if rc and onerr:

--- a/tests/test-push-http
+++ b/tests/test-push-http
@@ -39,11 +39,9 @@
 echo % expect success
 echo 'allow_push = *' >> .hg/hgrc
 echo '[hooks]' >> .hg/hgrc
-echo 'changegroup = python ../printenv.py changegroup 0 ../urls' >> .hg/hgrc
+echo 'changegroup = python ../printenv.py changegroup 0' >> .hg/hgrc
 req
 
-cat ../urls
-
 hg rollback
 echo % expect authorization error: all users denied
 echo '[web]' > .hg/hgrc

--- a/tests/test-push-http.out
+++ b/tests/test-push-http.out
@@ -23,8 +23,8 @@
 remote: adding manifests
 remote: adding file changes
 remote: added 1 changesets with 1 changes to 1 files
+remote: changegroup hook: HG_NODE=ba677d0156c1196c1a699fa53f390dcfc3ce3872 HG_SOURCE=serve HG_URL=remote:http 
 % serve errors
-changegroup hook: HG_NODE=ba677d0156c1196c1a699fa53f390dcfc3ce3872 HG_SOURCE=serve HG_URL=remote:http 
 rolling back to revision 0 (undo serve)
 % expect authorization error: all users denied
 abort: authorization failed