unbundle: acquire 'wlock' when processing bundle2 (BC) (issue4596)

A bundle2 may contain bookmark updates (or other extension content) that
requires the 'wlock' to be written. As 'wlock' must be acquired before 'lock',
we must stay on the side of caution and use both in all case to ensure their
ordering.

mercurial/exchange.py

@@ -10,6 +10,7 b' from node import hex, nullid'
 import errno, urllib
 import util, scmutil, changegroup, base85, error
 import discovery, phases, obsolete, bookmarks as bookmod, bundle2, pushkey
+import lock as lockmod
 
 def readbundle(ui, fh, fname, vfs=None):
     header = changegroup.readexactly(fh, 4)
@@ -1275,13 +1276,14 b' def unbundle(repo, cg, heads, source, ur'
     If the push was raced as PushRaced exception is raised."""
     r = 0
     # need a transaction when processing a bundle2 stream
-    tr = None
-    lock = repo.lock()
+    wlock = lock = tr = None
     try:
         check_heads(repo, heads, 'uploading changes')
         # push can proceed
         if util.safehasattr(cg, 'params'):
             try:
+                wlock = repo.wlock()
+                lock = repo.lock()
                 tr = repo.transaction(source)
                 tr.hookargs['source'] = source
                 tr.hookargs['url'] = url
@@ -1292,9 +1294,8 b' def unbundle(repo, cg, heads, source, ur'
                 exc.duringunbundle2 = True
                 raise
         else:
+            lock = repo.lock()
             r = changegroup.addchangegroup(repo, cg, source, url)
     finally:
-        if tr is not None:
-            tr.release()
-        lock.release()
+        lockmod.release(tr, lock, wlock)
     return r

tests/test-bundle2-exchange.t

@@ -226,7 +226,6 b' push'
   remote: adding file changes
   remote: added 1 changesets with 0 changes to 0 files (-1 heads)
   remote: 1 new obsolescence markers
-  remote: "wlock" acquired after "lock" at: */mercurial/bookmarks.py:259 (pushbookmark) (glob)
   updating bookmark book_eea1
   pre-close-tip:02de42196ebe draft book_02de
   postclose-tip:02de42196ebe draft book_02de
@@ -305,7 +304,6 b' push over ssh'
   remote: adding file changes
   remote: added 1 changesets with 1 changes to 1 files
   remote: 1 new obsolescence markers
-  remote: "wlock" acquired after "lock" at: */mercurial/bookmarks.py:259 (pushbookmark) (glob)
   updating bookmark book_5fdd
   remote: pre-close-tip:5fddd98957c8 draft book_5fdd
   remote: pushkey: lock state after "bookmarks"
@@ -357,7 +355,6 b' push over http'
   remote: adding file changes
   remote: added 1 changesets with 1 changes to 1 files
   remote: 1 new obsolescence markers
-  remote: "wlock" acquired after "lock" at: */mercurial/bookmarks.py:259 (pushbookmark) (glob)
   updating bookmark book_32af
   pre-close-tip:02de42196ebe draft book_02de
   postclose-tip:02de42196ebe draft book_02de