From 698f9e11961d5b42516e6aa7d4a8c26c64e8bc4d Mon Sep 17 00:00:00 2001
From: Min RK <benjaminrk@gmail.com>
Date: Wed, 24 May 2017 16:33:35 -0700
Subject: [PATCH] flush lines with carriage returns

for terminal progress bars
---
 repo2docker/utils.py | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/repo2docker/utils.py b/repo2docker/utils.py
index 051d463a..b3319edd 100644
--- a/repo2docker/utils.py
+++ b/repo2docker/utils.py
@@ -1,3 +1,4 @@
+from functools import partial
 import subprocess
 
 def execute_cmd(cmd, capture=False, **kwargs):
@@ -15,10 +16,22 @@ def execute_cmd(cmd, capture=False, **kwargs):
         if ret != 0:
             raise subprocess.CalledProcessError(ret, cmd)
         return
-
+    
+    buf = []
+    def flush():
+        line = b''.join(buf).decode('utf8', 'replace')
+        buf[:] = []
+        return line
+    
+    c_last = ''
     try:
-        for line in iter(proc.stdout.readline, b''):
-            yield line.decode('utf8', 'replace')
+        for c in iter(partial(proc.stdout.read, 1), b''):
+            if c_last == b'\r' and buf and c != b'\n':
+                yield flush()
+            buf.append(c)
+            if c == b'\n':
+                yield flush()
+            c_last = c
     finally:
         ret = proc.wait()
         if ret != 0: