mercurial/utils/procutil.py

--- a/mercurial/utils/procutil.py	Fri Apr 15 11:20:49 2022 -0400
+++ b/mercurial/utils/procutil.py	Tue Apr 19 10:53:58 2022 -0400
@@ -111,7 +111,9 @@
         total_to_write = len(s)
         total_written = 0
         while total_written < total_to_write:
-            total_written += write1(m[total_written:])
+            c = write1(m[total_written:])
+            if c:
+                total_written += c
         return total_written