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git: reluctantly give diff-highlight a try
I saw people talking about this a couple of weeks ago[1], but ignored it as I like to keep things simple, and I don't like the idea of slowing down the pager. Nevertheless, in my current sleep-deprived state, I feel like giving it a shot. I'm bundling a copy of the `diff-highlight` script from Git 2.6.1 because I want this to work everywhere that I use my dotfiles, without having to worry about `$PATH`, issues. Got it via: ``` cp "$(brew --prefix)/share/git-core/contrib/diff-highlight/diff-highlight" \ roles/dotfiles/files/.shells/bin ``` Note that I am using much more subtle color choices than seem to be the norm. (I don't really want this to shout at me, "HEY! LOOK! I AM A WORD THAT CHANGED!"; rather, I want diffs to pretty much look like diffs, and have some subtle cues to spot word differences when I actually need to. [1]: paulirish/dotfiles@6743b907
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,218 @@ | ||
#!/usr/bin/perl | ||
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use 5.008; | ||
use warnings FATAL => 'all'; | ||
use strict; | ||
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# Highlight by reversing foreground and background. You could do | ||
# other things like bold or underline if you prefer. | ||
my @OLD_HIGHLIGHT = ( | ||
color_config('color.diff-highlight.oldnormal'), | ||
color_config('color.diff-highlight.oldhighlight', "\x1b[7m"), | ||
color_config('color.diff-highlight.oldreset', "\x1b[27m") | ||
); | ||
my @NEW_HIGHLIGHT = ( | ||
color_config('color.diff-highlight.newnormal', $OLD_HIGHLIGHT[0]), | ||
color_config('color.diff-highlight.newhighlight', $OLD_HIGHLIGHT[1]), | ||
color_config('color.diff-highlight.newreset', $OLD_HIGHLIGHT[2]) | ||
); | ||
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my $RESET = "\x1b[m"; | ||
my $COLOR = qr/\x1b\[[0-9;]*m/; | ||
my $BORING = qr/$COLOR|\s/; | ||
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my @removed; | ||
my @added; | ||
my $in_hunk; | ||
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# Some scripts may not realize that SIGPIPE is being ignored when launching the | ||
# pager--for instance scripts written in Python. | ||
$SIG{PIPE} = 'DEFAULT'; | ||
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while (<>) { | ||
if (!$in_hunk) { | ||
print; | ||
$in_hunk = /^$COLOR*\@/; | ||
} | ||
elsif (/^$COLOR*-/) { | ||
push @removed, $_; | ||
} | ||
elsif (/^$COLOR*\+/) { | ||
push @added, $_; | ||
} | ||
else { | ||
show_hunk(\@removed, \@added); | ||
@removed = (); | ||
@added = (); | ||
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print; | ||
$in_hunk = /^$COLOR*[\@ ]/; | ||
} | ||
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# Most of the time there is enough output to keep things streaming, | ||
# but for something like "git log -Sfoo", you can get one early | ||
# commit and then many seconds of nothing. We want to show | ||
# that one commit as soon as possible. | ||
# | ||
# Since we can receive arbitrary input, there's no optimal | ||
# place to flush. Flushing on a blank line is a heuristic that | ||
# happens to match git-log output. | ||
if (!length) { | ||
local $| = 1; | ||
} | ||
} | ||
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# Flush any queued hunk (this can happen when there is no trailing context in | ||
# the final diff of the input). | ||
show_hunk(\@removed, \@added); | ||
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exit 0; | ||
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# Ideally we would feed the default as a human-readable color to | ||
# git-config as the fallback value. But diff-highlight does | ||
# not otherwise depend on git at all, and there are reports | ||
# of it being used in other settings. Let's handle our own | ||
# fallback, which means we will work even if git can't be run. | ||
sub color_config { | ||
my ($key, $default) = @_; | ||
my $s = `git config --get-color $key 2>/dev/null`; | ||
return length($s) ? $s : $default; | ||
} | ||
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sub show_hunk { | ||
my ($a, $b) = @_; | ||
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# If one side is empty, then there is nothing to compare or highlight. | ||
if (!@$a || !@$b) { | ||
print @$a, @$b; | ||
return; | ||
} | ||
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# If we have mismatched numbers of lines on each side, we could try to | ||
# be clever and match up similar lines. But for now we are simple and | ||
# stupid, and only handle multi-line hunks that remove and add the same | ||
# number of lines. | ||
if (@$a != @$b) { | ||
print @$a, @$b; | ||
return; | ||
} | ||
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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; | ||
} | ||
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sub highlight_pair { | ||
my @a = split_line(shift); | ||
my @b = split_line(shift); | ||
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# 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++; | ||
$pb++; | ||
} | ||
else { | ||
last; | ||
} | ||
} | ||
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# Find common suffix, ignoring colors. | ||
my ($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; | ||
} | ||
} | ||
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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); | ||
} | ||
} | ||
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sub split_line { | ||
local $_ = shift; | ||
return utf8::decode($_) ? | ||
map { utf8::encode($_); $_ } | ||
map { /$COLOR/ ? $_ : (split //) } | ||
split /($COLOR+)/ : | ||
map { /$COLOR/ ? $_ : (split //) } | ||
split /($COLOR+)/; | ||
} | ||
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sub highlight_line { | ||
my ($line, $prefix, $suffix, $theme) = @_; | ||
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my $start = join('', @{$line}[0..($prefix-1)]); | ||
my $mid = join('', @{$line}[$prefix..$suffix]); | ||
my $end = join('', @{$line}[($suffix+1)..$#$line]); | ||
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# 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], | ||
$end | ||
); | ||
} | ||
} | ||
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# Pairs are interesting to highlight only if we are going to end up | ||
# highlighting a subset (i.e., not the whole line). Otherwise, the highlighting | ||
# is just useless noise. We can detect this by finding either a matching prefix | ||
# or suffix (disregarding boring bits like whitespace and colorization). | ||
sub is_pair_interesting { | ||
my ($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]); | ||
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return $prefix_a !~ /^$COLOR*-$BORING*$/ || | ||
$prefix_b !~ /^$COLOR*\+$BORING*$/ || | ||
$suffix_a !~ /^$BORING*$/ || | ||
$suffix_b !~ /^$BORING*$/; | ||
} |
d079a03
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For reference, this is what it looks like with the chosen colors: