perf: fix `perfhelper-pathcopies` report of #changesets
The previous computation `<base>::<target>` was wrong, what we actually need is
`::<target> - ::<base>`.
This is now fixed
py3: use integer division in curseschunkselector.printstring()
This fixes a crash when scrolling in curses UI when refresh() is called
when a float value (namely 'self.firstlineofpadtoprint', taking its
value indirectly from 'self.linesprintedtopadsofar').
crecord: drop duplicated set of firstlineofpadtoprint attribute
The attribute is already set a couple of lines above, in
curseschunkselector.__init__().
py3: use email.generator.BytesGenerator in patch.split()
This fixes test-import.t on python3.
We add Generator alias in mail module to handle python2/python3
compatibility.
py3: only flush before prompting during interactive patch filtering
Follows up on
c9093ae8d6c4. It's enough to flush just before each
prompt.