[PATCH 2 of 4] devel: officially deprecate update without destination

[Pierre-Yves David]

# HG changeset patch
# User Pierre-Yves David <pierre-yves.david at ens-lyon.org>
# Date 1462469029 -7200
#      Thu May 05 19:23:49 2016 +0200
# Node ID cbb9caf8a54e5e6a6e9fe4b0e5f8f852d349d740
# Parent  70e701b45e36638fceffbb68d334b4f2478ecb76
# EXP-Topic deprecate
devel: officially deprecate update without destination

When we introduce the develwarning, we did not had an official deprecation API
and infrastructure. We can now officially deprecate the old way with a version
deadline.

diff -r 70e701b45e36 -r cbb9caf8a54e mercurial/merge.py
--- a/mercurial/merge.py	Thu May 05 19:23:30 2016 +0200
+++ b/mercurial/merge.py	Thu May 05 19:23:49 2016 +0200
@@ -1442,7 +1442,7 @@ def update(repo, node, branchmerge, forc
             pas = [repo[ancestor]]
 
         if node is None:
-            repo.ui.develwarn('update with no target', 'oldapi')
+            repo.ui.deprecwarn('update with no target', '3.9')
             rev, _mark, _act = destutil.destupdate(repo)
             node = repo[rev].node()