[PATCH 3 of 3 STABLE] devel-warn: issue a warning when writing bookmarks without holding the wlock

[Pierre-Yves David]

# HG changeset patch
# User Laurent Charignon <lcharignon at fb.com>
# Date 1438433019 25200
#      Sat Aug 01 05:43:39 2015 -0700
# Branch stable
# Node ID bb267085bdd69fff0f5fa4091bbc223889d57c0b
# Parent  3cfb0c92590589c9ccdef1884b6133d0d6303805
devel-warn: issue a warning when writing bookmarks without holding the wlock

I saw an issue in an extension that we develop where we were writing bookmarks
without holding the wlock. Another extension was taking a lock at the same time
and wiped out the bookmarks we were about to write. This patch adds a
devel-warning to urge people to fix their invalide code.

diff --git a/mercurial/bookmarks.py b/mercurial/bookmarks.py
--- a/mercurial/bookmarks.py
+++ b/mercurial/bookmarks.py
@@ -77,10 +77,15 @@ class bmstore(dict):
 
         We also store a backup of the previous state in undo.bookmarks that
         can be copied back on rollback.
         '''
         repo = self._repo
+        if (repo.ui.configbool('devel', 'all-warnings')
+                or repo.ui.configbool('devel', 'check-locks')):
+            l = repo._wlockref and repo._wlockref()
+            if l is None or not l.held:
+                repo.ui.develwarn('bookmarks write with no wlock')
         self._writerepo(repo)
         repo.invalidatevolatilesets()
 
     def _writerepo(self, repo):
         """Factored out for extensibility"""