# HG changeset patch
# User Yuya Nishihara <yuya@tcha.org>
# Date 1409413094 -7200
# Node ID a0e0aa12b672c7bfa0003cd842eaf170e32c9aa8
# Parent  149fc8a44184fbeddd9d9602e3860455e92c1301
util.system: avoid buffering of subprocess output when it is piped

util.system() copies subprocess' output through pipe if output file is not
stdout.  Because a file iterator has internal buffering, output won't be
flushed until enough data is available.  Therefore, it could easily miss
important messages such as "waiting for lock".

diff -r 149fc8a44184 -r a0e0aa12b672 mercurial/util.py
--- a/mercurial/util.py	Fri Oct 17 09:57:05 2014 +0900
+++ b/mercurial/util.py	Sat Aug 30 17:38:14 2014 +0200
@@ -649,7 +649,10 @@
             proc = subprocess.Popen(cmd, shell=True, close_fds=closefds,
                                     env=env, cwd=cwd, stdout=subprocess.PIPE,
                                     stderr=subprocess.STDOUT)
-            for line in proc.stdout:
+            while True:
+                line = proc.stdout.readline()
+                if not line:
+                    break
                 out.write(line)
             proc.wait()
             rc = proc.returncode