diff -r 84e8a6834223 -r a48c6ac5c13a mercurial/hook.py
--- a/mercurial/hook.py	Mon Mar 06 03:19:40 2017 -0800
+++ b/mercurial/hook.py	Mon Mar 06 03:09:15 2017 -0800
@@ -142,7 +142,7 @@
         cwd = repo.root
     else:
         cwd = pycompat.getcwd()
-    r = ui.system(cmd, environ=env, cwd=cwd)
+    r = ui.system(cmd, environ=env, cwd=cwd, blockedtag='exthook-%s' % (name,))
 
     duration = util.timer() - starttime
     ui.log('exthook', 'exthook-%s: %s finished in %0.2f seconds\n',