copies: show we can read data from the "first" mapping
In practice this make no difference since `t` is a copy of `a`. Having this
change before hand will make the next cleanup changeset clearer.
This is work on the road to using some native code for some performance critical
part of copy tracing.
--- a/mercurial/copies.py Wed Nov 13 20:33:22 2019 +0100
+++ b/mercurial/copies.py Wed Nov 13 20:45:34 2019 +0100
@@ -67,7 +67,7 @@
"""chain two sets of copies 'a' and 'b'"""
t = a.copy()
for k, v in pycompat.iteritems(b):
- t[k] = t.get(v, v)
+ t[k] = a.get(v, v)
return t