diff -r c9876c00d292 -r acd17caa699a mercurial/scmutil.py
--- a/mercurial/scmutil.py	Sun Nov 11 16:47:28 2018 +0900
+++ b/mercurial/scmutil.py	Wed Nov 14 11:30:46 2018 -0800
@@ -1166,7 +1166,7 @@
             wctx.copy(origsrc, dst)
 
 def writerequires(opener, requirements):
-    with opener('requires', 'w') as fp:
+    with opener('requires', 'w', atomictemp=True) as fp:
         for r in sorted(requirements):
             fp.write("%s\n" % r)