mq: fold the code path to invoke editor into specific logic (qnew)
This factoring simplifies the succeeding patch to switch from
"ui.edit()" to "getcommiteditor()" for qnew.
Check whether size of generaldelta revlog is not bigger than its
regular equivalent. Test would fail if generaldelta was naive
implementation of parentdelta: third manifest revision would be fully
inserted due to big distance from its paren revision (zero).
$ hg init repo
$ cd repo
$ echo foo > foo
$ echo bar > bar
$ hg commit -q -Am boo
$ hg clone --pull . ../gdrepo -q --config format.generaldelta=yes
$ for r in 1 2 3; do
> echo $r > foo
> hg commit -q -m $r
> hg up -q -r 0
> hg pull . -q -r $r -R ../gdrepo
> done
$ cd ..
>>> import os
>>> regsize = os.stat("repo/.hg/store/00manifest.i").st_size
>>> gdsize = os.stat("gdrepo/.hg/store/00manifest.i").st_size
>>> if regsize < gdsize:
... print 'generaldata increased size of manifest'