copy: to find copy source, walk parent of revision we're marking copies in As shown in the previous patch, `hg cp --after --at-rev . src dst` fails if `src` is not in `.`. It seems obvious that you should always walk the *parent* of the revision you're marking copies in, but that's not how it was done for the working copy, and I didn't think to change it when marking copies in a non-working-copy commit. This patch fixes that by walking the parent commit instead, but only if we're marking copies for a non-working-copy commit. We need to leave the working-copy code unchanged because it depends on the weird behavior of `workingctx.walk()`. With these changes, there's very little overlap between the working-copy version and the non-working-copy version of `walkpats()`, but I've refrained from cleaning that up on the stable branch. Differential Revision: https://phab.mercurial-scm.org/D8494

--- a/mercurial/cmdutil.py	Wed May 06 11:41:01 2020 -0700
+++ b/mercurial/cmdutil.py	Wed May 06 10:33:56 2020 -0700
@@ -1496,8 +1496,11 @@
 
     def walkpat(pat):
         srcs = []
-        m = scmutil.match(ctx, [pat], opts, globbed=True)
-        for abs in ctx.walk(m):
+        # TODO: Inline and simplify the non-working-copy version of this code
+        # since it shares very little with the working-copy version of it.
+        ctx_to_walk = ctx if ctx.rev() is None else pctx
+        m = scmutil.match(ctx_to_walk, [pat], opts, globbed=True)
+        for abs in ctx_to_walk.walk(m):
             rel = uipathfn(abs)
             exact = m.exact(abs)
             if abs not in ctx: