cleanup: prefer nested context managers to \-continuations

I'd prefer Python accept a tuple of context managers, but alas it
isn't meant to be. This will have to suffice.

Differential Revision: https://phab.mercurial-scm.org/D5994

hgext/largefiles/overrides.py

@@ -664,8 +664,8 b' def overridecopy(orig, ui, repo, pats, o'
                                   _('destination largefile already exists'))
             copiedfiles.append((src, dest))
             orig(src, dest, *args, **kwargs)
-        with extensions.wrappedfunction(util, 'copyfile', overridecopyfile), \
-             extensions.wrappedfunction(scmutil, 'match', overridematch):
+        with extensions.wrappedfunction(util, 'copyfile', overridecopyfile):
+            with extensions.wrappedfunction(scmutil, 'match', overridematch):
             result += orig(ui, repo, listpats, opts, rename)
 
         lfdirstate = lfutil.openlfdirstate(ui, repo)

hgext/narrow/narrowcommands.py

@@ -278,8 +278,8 b' def _widen(ui, repo, remote, commoninc, '
             p1, p2 = ds.p1(), ds.p2()
             with ds.parentchange():
                 ds.setparents(node.nullid, node.nullid)
-            with wrappedextraprepare,\
-                 repo.ui.configoverride(overrides, 'widen'):
+            with wrappedextraprepare:
+                with repo.ui.configoverride(overrides, 'widen'):
                 exchange.pull(repo, remote, heads=common)
             with ds.parentchange():
                 ds.setparents(p1, p2)
@@ -296,8 +296,8 b' def _widen(ui, repo, remote, commoninc, '
                     'ellipses': False,
                 }).result()
 
-            with repo.transaction('widening') as tr,\
-                 repo.ui.configoverride(overrides, 'widen'):
+            with repo.transaction('widening') as tr:
+                with repo.ui.configoverride(overrides, 'widen'):
                 tgetter = lambda: tr
                 bundle2.processbundle(repo, bundle,
                         transactiongetter=tgetter)

mercurial/exchange.py

@@ -556,9 +556,9 b' def push(repo, remote, force=False, revs'
                % stringutil.forcebytestr(err))
         pushop.ui.debug(msg)
 
-    with wlock or util.nullcontextmanager(), \
-            lock or util.nullcontextmanager(), \
-            pushop.trmanager or util.nullcontextmanager():
+    with wlock or util.nullcontextmanager():
+        with lock or util.nullcontextmanager():
+            with pushop.trmanager or util.nullcontextmanager():
         pushop.repo.checkpush(pushop)
         _checkpublish(pushop)
         _pushdiscovery(pushop)