D2686: xdiff: add a preprocessing step that trims files

[quark (Jun Wu)]

quark added a comment.


  I'll do the rebase (probably tomorrow). It will make the `xdl_do_diff2` change unnecessary, and maybe rename `prefix_lines` etc to be more like the original code. But the main feature (xdl_trim_files) will probably stay unchanged and is worth a look now.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D2686

To: quark, #hg-reviewers
Cc: indygreg, mercurial-devel