py3: introduce pycompat.ziplist as zip is a generator on Python 3

Similar to map, the return value of zip was also turned into a generator on
Python 3. We have multiple occurences in our codebase where we retrieve the
values of zip multiple times, so let's introduce pycompat.ziplist similar to
pycompat.maplist.

Differential Revision: https://phab.mercurial-scm.org/D1675

mercurial/pycompat.py

@@ -63,6 +63,7 b' if ispy3:'
         sysexecutable = os.fsencode(sysexecutable)
     stringio = io.BytesIO
     maplist = lambda *args: list(map(*args))
+    ziplist = lambda *args: list(zip(*args))
     rawinput = input
 
     # TODO: .buffer might not exist if std streams were replaced; we'll need
@@ -313,6 +314,7 b' else:'
     shlexsplit = shlex.split
     stringio = cStringIO.StringIO
     maplist = map
+    ziplist = zip
     rawinput = raw_input
 
 isjython = sysplatform.startswith('java')