# HG changeset patch
# User Pierre-Yves David <pierre-yves.david@octobus.net>
# Date 1605865126 -3600
# Node ID b6b7626d3e06334d13de7eeb7514d6b0515a17f5
# Parent  fada33872b5bbbd857110d53e3068456a8c7401a
copies: avoid unwanted side effect from one branch to another

Without this copy, change in a one descendant branch (With "remove" change
only) could affect computation on another descendant branches.

This was not caugh by the test because the test graph are "too simple". I
started writing more test in that regards, but I a submitting this changes
earlier because I want to get more code landed to allow other optimisation work
to happens.

Differential Revision: https://phab.mercurial-scm.org/D9416

diff -r fada33872b5b -r b6b7626d3e06 mercurial/copies.py
--- a/mercurial/copies.py	Thu Nov 26 09:54:16 2020 +0100
+++ b/mercurial/copies.py	Fri Nov 20 10:38:46 2020 +0100
@@ -354,7 +354,9 @@
                         source = prev[1]
                     newcopies[dest] = (c, source)
                 assert newcopies is not copies
-            if changes is not None:
+            if changes is not None and changes.removed:
+                if newcopies is copies:
+                    newcopies = copies.copy()
                 for f in changes.removed:
                     if f in newcopies:
                         if newcopies is copies: