diff: add --ignore-blank-lines option

The goal of the patch is to introduce the GNU diff
-B/--ignore-blank-lines as closely as possible. The short option is not
available because it's already used for "break-rewrites".

When this option is used, git-diff will not create hunks that simply
add or remove empty lines, but will still show empty lines
addition/suppression if they are close enough to "valuable" changes.

There are two differences between this option and GNU diff -B option:
- GNU diff doesn't have "--inter-hunk-context", so this must be handled
- The following sequence looks like a bug (context is displayed twice):

    $ seq 5 >file1
    $ cat <<EOF >file2
    change
    1
    2

    3
    4
    5
    change
    EOF
    $ diff -u -B file1 file2
    --- file1	2013-06-08 22:13:04.471517834 +0200
    +++ file2	2013-06-08 22:13:23.275517855 +0200
    @@ -1,5 +1,7 @@
    +change
     1
     2
    +
     3
     4
     5
    @@ -3,3 +5,4 @@
     3
     4
     5
    +change

So here is a more thorough description of the option:
- real changes are interesting
- blank lines that are close enough (less than context size) to
interesting changes are considered interesting (recursive definition)
- "context" lines are used around each hunk of interesting changes
- If two hunks are separated by less than "inter-hunk-context", they
will be merged into one.

The implementation does the "interesting changes selection" in a single
pass.

Signed-off-by: Antoine Pelisse <apelisse@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/xdiff/xemit.h b/xdiff/xemit.h
index c2e2e83..d297107 100644
--- a/xdiff/xemit.h
+++ b/xdiff/xemit.h
@@ -27,7 +27,7 @@
 typedef int (*emit_func_t)(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 			   xdemitconf_t const *xecfg);
 
-xdchange_t *xdl_get_hunk(xdchange_t *xscr, xdemitconf_t const *xecfg);
+xdchange_t *xdl_get_hunk(xdchange_t **xscr, xdemitconf_t const *xecfg);
 int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 		  xdemitconf_t const *xecfg);