Subject: Re: [Bug?] log -p -W showing the whole file for a patch that adds to the end?

From: René Scharfe <[email-masked]>
Date: Sat, 21 May 2016 20:42:48 +0200

Am 11.05.2016 um 00:51 schrieb Junio C Hamano:
> The helper function get_func_line() however gets confused when a
> hunk adds a new function at the very end, and returns -1 to signal
> that it did not find a suitable "function header line", i.e. the
> beginning of previous function.  The caller then takes this signal
> and shows from the very beginning of the file.  We end up showing
> the entire file, starting from the very beginning to the end of the
> newly added lines.

In this case we need to look at the added lines in the post-image to
see if the original context suffices.  We currently only look at the
pre-image.  And if we have to extend the context simply search from the
bottom of the pre-image.  That's what the second patch does; the first
one is just a small preparation.

The last three patches introduce special handling of empty lines.
Before them the code for -W only distinguished between function lines
and non-function lines.  Not allowing empty lines between functions to
extend the context with -W is most useful in the case of appended full
functions -- otherwise we'd get the preceding function shown as well as
it "belongs" to the empty line separating them.

And if we do that then it's easy and more consistent to stop showing
empty lines trailing functions with -W (unless they're already included
in the one requested with -u/-U, of course).  Doing the same for grep
then is only fair.

Considering empty lines as uninteresting collides with languages like
Whitespace.  I'm not sure -W was useful for it to begin with, though.
Any other possible downsides?

NB: Comments are still not handled specially.  That means they are
considered to be part of the preceding function.  Fixing that is not in
scope for this series.  (And I'm not sure it would be worth the hassle.)

  diff: factor out match_func_rec()
  diff: handle appended chunks better with -W
  diff: ignore empty lines before added functions with -W
  diff: don't include common trailing empty lines with -W
  grep: don't extend context to trailing empty lines with -W

 grep.c        | 28 ++++++++++++++++++++++++--
 xdiff/xemit.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 82 insertions(+), 9 deletions(-)