On Thu, Jun 18, 2015 at 04:45:05PM -0400, Jeff King wrote:
> Still, I think this is probably a minority case, and it may be
> outweighed by the improvements. The "real" solution is to consider the
> hunk as a whole and do an LCS diff on it, which would show that yes,
> it's worth highlighting both of those spots, as they are a small
> percentage of the total hunk.
I've been meaning to play with this for years, so I took the opportunity
to spend a little time on it. :)
Below is a (slightly hacky) patch I came up with. It seems to work, and
produces really great output in some cases. For instance, in 99a2cfb, it
produces (I put highlighted bits in angle brackets):
- <hash>cpy(peeled, <sha1>);
+ <oid>cpy(<&>peeled, <oid>);
It also produces nonsense like:
- <un>s<ign>ed <char >peeled<[20]>;
+ s<truct obj>e<ct_i>d peeled;
but I think that is simply because my splitting function is terrible (it
splits each byte, whereas we'd probably want to use whitespace and
punctuation, or something content-specific).
---
diff --git a/contrib/diff-highlight/diff-highlight
b/contrib/diff-highlight/diff-highlight
index ffefc31..7165518 100755
--- a/contrib/diff-highlight/diff-highlight
+++ b/contrib/diff-highlight/diff-highlight
@@ -3,6 +3,7 @@
use 5.008;
use warnings FATAL => 'all';
use strict;
+use Algorithm::Diff;
# Highlight by reversing foreground and background. You could do
# other things like bold or underline if you prefer.
@@ -88,131 +89,54 @@ sub show_hunk {
return;
}
- # If we have mismatched numbers of lines on each side, we could try to
- # be clever and match up similar lines. But for now we are simple and
- # stupid, and only handle multi-line hunks that remove and add the same
- # number of lines.
- if (@$a != @$b) {
- print @$a, @$b;
- return;
- }
-
- my @queue;
- for (my $i = 0; $i < @$a; $i++) {
- my ($rm, $add) = highlight_pair($a->[$i], $b->[$i]);
- print $rm;
- push @queue, $add;
- }
- print @queue;
-}
-
-sub highlight_pair {
- my @a = split_line(shift);
- my @b = split_line(shift);
+ my ($prefix_a, $suffix_a, @hunk_a) = split_hunk(@$a);
+ my ($prefix_b, $suffix_b, @hunk_b) = split_hunk(@$b);
- # Find common prefix, taking care to skip any ansi
- # color codes.
- my $seen_plusminus;
- my ($pa, $pb) = (0, 0);
- while ($pa < @a && $pb < @b) {
- if ($a[$pa] =~ /$COLOR/) {
- $pa++;
- }
- elsif ($b[$pb] =~ /$COLOR/) {
- $pb++;
- }
- elsif ($a[$pa] eq $b[$pb]) {
- $pa++;
- $pb++;
- }
- elsif (!$seen_plusminus && $a[$pa] eq '-' && $b[$pb] eq '+') {
- $seen_plusminus = 1;
- $pa++;
- $pb++;
- }
- else {
- last;
- }
- }
+ my $diff = Algorithm::Diff->new(\@hunk_a, \@hunk_b);
+ my (@out_a, @out_b);
+ while ($diff->Next()) {
+ my $bits = $diff->Diff();
- # Find common suffix, ignoring colors.
- my ($sa, $sb) = ($#a, $#b);
- while ($sa >= $pa && $sb >= $pb) {
- if ($a[$sa] =~ /$COLOR/) {
- $sa--;
- }
- elsif ($b[$sb] =~ /$COLOR/) {
- $sb--;
- }
- elsif ($a[$sa] eq $b[$sb]) {
- $sa--;
- $sb--;
- }
- else {
- last;
- }
- }
+ push @out_a, $OLD_HIGHLIGHT[1] if $bits & 1;
+ push @out_a, $diff->Items(1);
+ push @out_a, $OLD_HIGHLIGHT[2] if $bits & 1;
- if (is_pair_interesting(\@a, $pa, $sa, \@b, $pb, $sb)) {
- return highlight_line(\@a, $pa, $sa, \@OLD_HIGHLIGHT),
- highlight_line(\@b, $pb, $sb, \@NEW_HIGHLIGHT);
- }
- else {
- return join('', @a),
- join('', @b);
+ push @out_b, $NEW_HIGHLIGHT[1] if $bits & 2;
+ push @out_b, $diff->Items(2);
+ push @out_b, $NEW_HIGHLIGHT[2] if $bits & 2;
}
-}
-sub split_line {
- local $_ = shift;
- return utf8::decode($_) ?
- map { utf8::encode($_); $_ }
- map { /$COLOR/ ? $_ : (split //) }
- split /($COLOR+)/ :
- map { /$COLOR/ ? $_ : (split //) }
- split /($COLOR+)/;
+ output_split_hunk($prefix_a, $suffix_a, @out_a);
+ output_split_hunk($prefix_b, $suffix_b, @out_b);
}
-sub highlight_line {
- my ($line, $prefix, $suffix, $theme) = @_;
-
- my $start = join('', @{$line}[0..($prefix-1)]);
- my $mid = join('', @{$line}[$prefix..$suffix]);
- my $end = join('', @{$line}[($suffix+1)..$#$line]);
-
- # If we have a "normal" color specified, then take over the whole line.
- # Otherwise, we try to just manipulate the highlighted bits.
- if (defined $theme->[0]) {
- s/$COLOR//g for ($start, $mid, $end);
- chomp $end;
- return join('',
- $theme->[0], $start, $RESET,
- $theme->[1], $mid, $RESET,
- $theme->[0], $end, $RESET,
- "\n"
- );
- } else {
- return join('',
- $start,
- $theme->[1], $mid, $theme->[2],
- $end
- );
+# Return the individual diff-able items of the hunk, but with any
+# diff or color prefix/suffix for each line split out (we assume that the
+# prefix/suffix for each line will be the same).
+sub split_hunk {
+ my ($prefix, $suffix, @r);
+ foreach my $line (@_) {
+ $line =~ /^($COLOR*[+-]$COLOR*)(.*)($COLOR*)/
+ or die "eh, this is supposed to match everything!";
+
+ # overwrite the old values; we assume they're all the same
+ # anyway
+ $prefix = $1;
+ $suffix = $3;
+
+ # do a straight character split. This almost certainly isn't
+ # ideal, but it's a good starting point. We should at the very
+ # least be utf8-aware, and probably use color-words regexes.
+ push @r, split(//, $2), "\n";
}
+ return ($prefix, $suffix, @r);
}
-# Pairs are interesting to highlight only if we are going to end up
-# highlighting a subset (i.e., not the whole line). Otherwise, the highlighting
-# is just useless noise. We can detect this by finding either a matching prefix
-# or suffix (disregarding boring bits like whitespace and colorization).
-sub is_pair_interesting {
- my ($a, $pa, $sa, $b, $pb, $sb) = @_;
- my $prefix_a = join('', @$a[0..($pa-1)]);
- my $prefix_b = join('', @$b[0..($pb-1)]);
- my $suffix_a = join('', @$a[($sa+1)..$#$a]);
- my $suffix_b = join('', @$b[($sb+1)..$#$b]);
-
- return $prefix_a !~ /^$COLOR*-$BORING*$/ ||
- $prefix_b !~ /^$COLOR*\+$BORING*$/ ||
- $suffix_a !~ /^$BORING*$/ ||
- $suffix_b !~ /^$BORING*$/;
+sub output_split_hunk {
+ my $prefix = shift;
+ my $suffix = shift;
+ my $str = join('', @_);
+ $str =~ s/^/$prefix/mg;
+ $str =~ s/$/$suffix/mg;
+ print $str;
}
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