Merge branch 'ah/doc-gitattributes-empty-index' into maint
[git/git.git] / contrib / diff-highlight / DiffHighlight.pm
1 package DiffHighlight;
2
3 use 5.008;
4 use warnings FATAL => 'all';
5 use strict;
6
7 # Highlight by reversing foreground and background. You could do
8 # other things like bold or underline if you prefer.
9 my @OLD_HIGHLIGHT = (
10 color_config('color.diff-highlight.oldnormal'),
11 color_config('color.diff-highlight.oldhighlight', "\x1b[7m"),
12 color_config('color.diff-highlight.oldreset', "\x1b[27m")
13 );
14 my @NEW_HIGHLIGHT = (
15 color_config('color.diff-highlight.newnormal', $OLD_HIGHLIGHT[0]),
16 color_config('color.diff-highlight.newhighlight', $OLD_HIGHLIGHT[1]),
17 color_config('color.diff-highlight.newreset', $OLD_HIGHLIGHT[2])
18 );
19
20 my $RESET = "\x1b[m";
21 my $COLOR = qr/\x1b\[[0-9;]*m/;
22 my $BORING = qr/$COLOR|\s/;
23
24 # The patch portion of git log -p --graph should only ever have preceding | and
25 # not / or \ as merge history only shows up on the commit line.
26 my $GRAPH = qr/$COLOR?\|$COLOR?\s+/;
27
28 my @removed;
29 my @added;
30 my $in_hunk;
31
32 our $line_cb = sub { print @_ };
33 our $flush_cb = sub { local $| = 1 };
34
35 sub handle_line {
36 local $_ = shift;
37
38 if (!$in_hunk) {
39 $line_cb->($_);
40 $in_hunk = /^$GRAPH*$COLOR*\@\@ /;
41 }
42 elsif (/^$GRAPH*$COLOR*-/) {
43 push @removed, $_;
44 }
45 elsif (/^$GRAPH*$COLOR*\+/) {
46 push @added, $_;
47 }
48 else {
49 show_hunk(\@removed, \@added);
50 @removed = ();
51 @added = ();
52
53 $line_cb->($_);
54 $in_hunk = /^$GRAPH*$COLOR*[\@ ]/;
55 }
56
57 # Most of the time there is enough output to keep things streaming,
58 # but for something like "git log -Sfoo", you can get one early
59 # commit and then many seconds of nothing. We want to show
60 # that one commit as soon as possible.
61 #
62 # Since we can receive arbitrary input, there's no optimal
63 # place to flush. Flushing on a blank line is a heuristic that
64 # happens to match git-log output.
65 if (!length) {
66 $flush_cb->();
67 }
68 }
69
70 sub flush {
71 # Flush any queued hunk (this can happen when there is no trailing
72 # context in the final diff of the input).
73 show_hunk(\@removed, \@added);
74 }
75
76 sub highlight_stdin {
77 while (<STDIN>) {
78 handle_line($_);
79 }
80 flush();
81 }
82
83 # Ideally we would feed the default as a human-readable color to
84 # git-config as the fallback value. But diff-highlight does
85 # not otherwise depend on git at all, and there are reports
86 # of it being used in other settings. Let's handle our own
87 # fallback, which means we will work even if git can't be run.
88 sub color_config {
89 my ($key, $default) = @_;
90 my $s = `git config --get-color $key 2>/dev/null`;
91 return length($s) ? $s : $default;
92 }
93
94 sub show_hunk {
95 my ($a, $b) = @_;
96
97 # If one side is empty, then there is nothing to compare or highlight.
98 if (!@$a || !@$b) {
99 $line_cb->(@$a, @$b);
100 return;
101 }
102
103 # If we have mismatched numbers of lines on each side, we could try to
104 # be clever and match up similar lines. But for now we are simple and
105 # stupid, and only handle multi-line hunks that remove and add the same
106 # number of lines.
107 if (@$a != @$b) {
108 $line_cb->(@$a, @$b);
109 return;
110 }
111
112 my @queue;
113 for (my $i = 0; $i < @$a; $i++) {
114 my ($rm, $add) = highlight_pair($a->[$i], $b->[$i]);
115 $line_cb->($rm);
116 push @queue, $add;
117 }
118 $line_cb->(@queue);
119 }
120
121 sub highlight_pair {
122 my @a = split_line(shift);
123 my @b = split_line(shift);
124
125 # Find common prefix, taking care to skip any ansi
126 # color codes.
127 my $seen_plusminus;
128 my ($pa, $pb) = (0, 0);
129 while ($pa < @a && $pb < @b) {
130 if ($a[$pa] =~ /$COLOR/) {
131 $pa++;
132 }
133 elsif ($b[$pb] =~ /$COLOR/) {
134 $pb++;
135 }
136 elsif ($a[$pa] eq $b[$pb]) {
137 $pa++;
138 $pb++;
139 }
140 elsif (!$seen_plusminus && $a[$pa] eq '-' && $b[$pb] eq '+') {
141 $seen_plusminus = 1;
142 $pa++;
143 $pb++;
144 }
145 else {
146 last;
147 }
148 }
149
150 # Find common suffix, ignoring colors.
151 my ($sa, $sb) = ($#a, $#b);
152 while ($sa >= $pa && $sb >= $pb) {
153 if ($a[$sa] =~ /$COLOR/) {
154 $sa--;
155 }
156 elsif ($b[$sb] =~ /$COLOR/) {
157 $sb--;
158 }
159 elsif ($a[$sa] eq $b[$sb]) {
160 $sa--;
161 $sb--;
162 }
163 else {
164 last;
165 }
166 }
167
168 if (is_pair_interesting(\@a, $pa, $sa, \@b, $pb, $sb)) {
169 return highlight_line(\@a, $pa, $sa, \@OLD_HIGHLIGHT),
170 highlight_line(\@b, $pb, $sb, \@NEW_HIGHLIGHT);
171 }
172 else {
173 return join('', @a),
174 join('', @b);
175 }
176 }
177
178 # we split either by $COLOR or by character. This has the side effect of
179 # leaving in graph cruft. It works because the graph cruft does not contain "-"
180 # or "+"
181 sub split_line {
182 local $_ = shift;
183 return utf8::decode($_) ?
184 map { utf8::encode($_); $_ }
185 map { /$COLOR/ ? $_ : (split //) }
186 split /($COLOR+)/ :
187 map { /$COLOR/ ? $_ : (split //) }
188 split /($COLOR+)/;
189 }
190
191 sub highlight_line {
192 my ($line, $prefix, $suffix, $theme) = @_;
193
194 my $start = join('', @{$line}[0..($prefix-1)]);
195 my $mid = join('', @{$line}[$prefix..$suffix]);
196 my $end = join('', @{$line}[($suffix+1)..$#$line]);
197
198 # If we have a "normal" color specified, then take over the whole line.
199 # Otherwise, we try to just manipulate the highlighted bits.
200 if (defined $theme->[0]) {
201 s/$COLOR//g for ($start, $mid, $end);
202 chomp $end;
203 return join('',
204 $theme->[0], $start, $RESET,
205 $theme->[1], $mid, $RESET,
206 $theme->[0], $end, $RESET,
207 "\n"
208 );
209 } else {
210 return join('',
211 $start,
212 $theme->[1], $mid, $theme->[2],
213 $end
214 );
215 }
216 }
217
218 # Pairs are interesting to highlight only if we are going to end up
219 # highlighting a subset (i.e., not the whole line). Otherwise, the highlighting
220 # is just useless noise. We can detect this by finding either a matching prefix
221 # or suffix (disregarding boring bits like whitespace and colorization).
222 sub is_pair_interesting {
223 my ($a, $pa, $sa, $b, $pb, $sb) = @_;
224 my $prefix_a = join('', @$a[0..($pa-1)]);
225 my $prefix_b = join('', @$b[0..($pb-1)]);
226 my $suffix_a = join('', @$a[($sa+1)..$#$a]);
227 my $suffix_b = join('', @$b[($sb+1)..$#$b]);
228
229 return $prefix_a !~ /^$GRAPH*$COLOR*-$BORING*$/ ||
230 $prefix_b !~ /^$GRAPH*$COLOR*\+$BORING*$/ ||
231 $suffix_a !~ /^$BORING*$/ ||
232 $suffix_b !~ /^$BORING*$/;
233 }