tests/test-gendoc.t

wrapfunction: use functools.partial if possible

Every `extensions.bind` call inserts a frame in traceback:

   ... in closure
     return func(*(args + a), **kw)

which makes traceback noisy.

The Python stdlib has a `functools.partial` which is backed by C code and
does not pollute traceback. However it does not support instancemethod and
sets `args` attribute which could be problematic for alias handling.

This patch makes `wrapfunction` use `functools.partial` if we are wrapping a
function directly exported by a module (so it's impossible to be a class or
instance method), and special handles `wrapfunction` results so alias
handling code could handle `args` just fine.

As an example, `hg rebase -s . -d . --traceback` got 6 lines removed in my
setup:

   File "hg/mercurial/dispatch.py", line 898, in _dispatch
     cmdpats, cmdoptions)
  -File "hg/mercurial/extensions.py", line 333, in closure
  -  return func(*(args + a), **kw)
   File "hg/hgext/journal.py", line 84, in runcommand
     return orig(lui, repo, cmd, fullargs, *args)
  -File "hg/mercurial/extensions.py", line 333, in closure
  -  return func(*(args + a), **kw)
   File "fb-hgext/hgext3rd/fbamend/hiddenoverride.py", line 119, in runcommand
     result = orig(lui, repo, cmd, fullargs, *args)
   File "hg/mercurial/dispatch.py", line 660, in runcommand
     ret = _runcommand(ui, options, cmd, d)
  -File "hg/mercurial/extensions.py", line 333, in closure
  -  return func(*(args + a), **kw)
   File "hg/hgext/pager.py", line 69, in pagecmd
     return orig(ui, options, cmd, cmdfunc)
   ....

Differential Revision: https://phab.mercurial-scm.org/D632

#require docutils
#require gettext

Test document extraction

  $ HGENCODING=UTF-8
  $ export HGENCODING
  $ { echo C; ls "$TESTDIR/../i18n"/*.po | sort; } | while read PO; do
  >     LOCALE=`basename "$PO" .po`
  >     echo "% extracting documentation from $LOCALE"
  >     LANGUAGE=$LOCALE $PYTHON "$TESTDIR/../doc/gendoc.py" >> gendoc-$LOCALE.txt 2> /dev/null || exit
  > 
  >     if [ $LOCALE != C ]; then
  >         if [ ! -f $TESTDIR/test-gendoc-$LOCALE.t ]; then
  >             echo missing test-gendoc-$LOCALE.t
  >         fi
  >         cmp -s gendoc-C.txt gendoc-$LOCALE.txt && echo "** NOTHING TRANSLATED ($LOCALE) **"
  >     fi
  > done; true
  % extracting documentation from C
  % extracting documentation from da
  % extracting documentation from de
  % extracting documentation from el
  % extracting documentation from fr
  % extracting documentation from it
  % extracting documentation from ja
  % extracting documentation from pt_BR
  % extracting documentation from ro
  % extracting documentation from ru
  % extracting documentation from sv
  % extracting documentation from zh_CN
  % extracting documentation from zh_TW