D7808: mmap: add a size argument to mmapread

[durin42 (Augie Fackler)]

durin42 added inline comments.

INLINE COMMENTS

> marmoute wrote in util.py:419-422
> passing 0 in `mmap.mmap(fd, 0, access=mmap.ACCESS_READ)` get you "all the byte you can eat". That's is not 0 sized mmap.
> 
> The `size` argument for `util.mmapread` is (after this patch). If size is None "all you can eat". if size is specified: provided exactly that amount of bytes.

This merits a comment. I'll add one in flight.

REPOSITORY
  rHG Mercurial

CHANGES SINCE LAST ACTION
  https://phab.mercurial-scm.org/D7808/new/

REVISION DETAIL
  https://phab.mercurial-scm.org/D7808

To: marmoute, #hg-reviewers
Cc: durin42, mharbison72, mercurial-devel