apveyor, gitpython-developers#519: FIX incomplete Popen pump

+ Pump once, so when input larger than `mmap.PAGESIZE`, stream is not
emptied.

Author: ankostis

git/cmd.py

@@ -100,16 +100,16 @@ def _parse_lines_from_buffer(buf):
     # end
 
     def _read_lines_from_fno(fno, last_buf_list):
-        buf = os.read(fno, mmap.PAGESIZE)
-        buf = last_buf_list[0] + buf
+        for buf in iter(lambda: os.read(fno, mmap.PAGESIZE), b''):
+            buf = last_buf_list[0] + buf
 
-        bi = 0
-        for bi, line in _parse_lines_from_buffer(buf):
-            yield line
-        # for each line to parse from the buffer
+            bi = 0
+            for bi, line in _parse_lines_from_buffer(buf):
+                yield line
+            # for each line to parse from the buffer
 
-        # keep remainder
-        last_buf_list[0] = buf[bi:]
+            # keep remainder
+            last_buf_list[0] = buf[bi:]
 
     def _dispatch_single_line(line, handler):
         line = line.decode(defenc)