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-rw-r--r--contrib/diff-highlight/README16
-rwxr-xr-xcontrib/diff-highlight/diff-highlight70
2 files changed, 52 insertions, 34 deletions
diff --git a/contrib/diff-highlight/README b/contrib/diff-highlight/README
index 1b7b6df..4a58579 100644
--- a/contrib/diff-highlight/README
+++ b/contrib/diff-highlight/README
@@ -14,13 +14,15 @@ Instead, this script post-processes the line-oriented diff, finds pairs
of lines, and highlights the differing segments. It's currently very
simple and stupid about doing these tasks. In particular:
- 1. It will only highlight a pair of lines if they are the only two
- lines in a hunk. It could instead try to match up "before" and
- "after" lines for a given hunk into pairs of similar lines.
- However, this may end up visually distracting, as the paired
- lines would have other highlighted lines in between them. And in
- practice, the lines which most need attention called to their
- small, hard-to-see changes are touching only a single line.
+ 1. It will only highlight hunks in which the number of removed and
+ added lines is the same, and it will pair lines within the hunk by
+ position (so the first removed line is compared to the first added
+ line, and so forth). This is simple and tends to work well in
+ practice. More complex changes don't highlight well, so we tend to
+ exclude them due to the "same number of removed and added lines"
+ restriction. Or even if we do try to highlight them, they end up
+ not highlighting because of our "don't highlight if the whole line
+ would be highlighted" rule.
2. It will find the common prefix and suffix of two lines, and
consider everything in the middle to be "different". It could
diff --git a/contrib/diff-highlight/diff-highlight b/contrib/diff-highlight/diff-highlight
index 279d211..c4404d4 100755
--- a/contrib/diff-highlight/diff-highlight
+++ b/contrib/diff-highlight/diff-highlight
@@ -10,23 +10,28 @@ my $UNHIGHLIGHT = "\x1b[27m";
my $COLOR = qr/\x1b\[[0-9;]*m/;
my $BORING = qr/$COLOR|\s/;
-my @window;
+my @removed;
+my @added;
+my $in_hunk;
while (<>) {
- # We highlight only single-line changes, so we need
- # a 4-line window to make a decision on whether
- # to highlight.
- push @window, $_;
- next if @window < 4;
- if ($window[0] =~ /^$COLOR*(\@| )/ &&
- $window[1] =~ /^$COLOR*-/ &&
- $window[2] =~ /^$COLOR*\+/ &&
- $window[3] !~ /^$COLOR*\+/) {
- print shift @window;
- show_hunk(shift @window, shift @window);
+ if (!$in_hunk) {
+ print;
+ $in_hunk = /^$COLOR*\@/;
+ }
+ elsif (/^$COLOR*-/) {
+ push @removed, $_;
+ }
+ elsif (/^$COLOR*\+/) {
+ push @added, $_;
}
else {
- print shift @window;
+ show_hunk(\@removed, \@added);
+ @removed = ();
+ @added = ();
+
+ print;
+ $in_hunk = /^$COLOR*[\@ ]/;
}
# Most of the time there is enough output to keep things streaming,
@@ -42,26 +47,37 @@ while (<>) {
}
}
-# Special case a single-line hunk at the end of file.
-if (@window == 3 &&
- $window[0] =~ /^$COLOR*(\@| )/ &&
- $window[1] =~ /^$COLOR*-/ &&
- $window[2] =~ /^$COLOR*\+/) {
- print shift @window;
- show_hunk(shift @window, shift @window);
-}
-
-# And then flush any remaining lines.
-while (@window) {
- print shift @window;
-}
+# Flush any queued hunk (this can happen when there is no trailing context in
+# the final diff of the input).
+show_hunk(\@removed, \@added);
exit 0;
sub show_hunk {
my ($a, $b) = @_;
- print highlight_pair($a, $b);
+ # If one side is empty, then there is nothing to compare or highlight.
+ if (!@$a || !@$b) {
+ print @$a, @$b;
+ return;
+ }
+
+ # If we have mismatched numbers of lines on each side, we could try to
+ # be clever and match up similar lines. But for now we are simple and
+ # stupid, and only handle multi-line hunks that remove and add the same
+ # number of lines.
+ if (@$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 {