The algorithm in diff-highlight only understands how to look
at two sides of a diff; it cannot correctly handle combined
diffs with multiple preimages. Often highlighting does not
trigger at all for these diffs because the line counts do
not match up. E.g., if we see:
- ours
-theirs
++resolved
we would not bother highlighting; it naively looks like a
single line went away, and then a separate hunk added
another single line.
But of course there are exceptions. E.g., if the other side
deleted the line, we might see:
- ours
++resolved
which looks like we dropped " ours" and added "+resolved".
This is only a small highlighting glitch (we highlight the
space and the "+" along with the content), but it's also the
tip of the iceberg. Even if we learned to find the true
content here (by noticing we are in a 3-way combined diff
and marking _two_ characters from the front of the line as
uninteresting), there are other more complicated cases where
we really do need to handle a 3-way hunk.
Let's just punt for now; we can recognize combined diffs by
the presence of extra "@" symbols in the hunk header, and
treat them as non-diff content.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Now that we have a test suite for diff highlight, we can
show off the improvements from 8d00662 (diff-highlight: do
not split multibyte characters, 2015-04-03).
While we're at it, we can also add another case that
_doesn't_ work: combining code points are treated as their
own unit, which means that we may stick colors between them
and the character they are modifying (with the result that
the color is not shown in an xterm, though it's possible
that other terminals err the other way, and show the color
but not the accent). There's no fix here, but let's
document it as a failure.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
These are the same as in the normal t/.gitignore, with the
exception of ".prove", as our Makefile does not support it.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
"diff-highlight" (in contrib/) used to show byte-by-byte
differences, which meant that multi-byte characters can be chopped
in the middle. It learned to pay attention to character boundaries
(assuming the UTF-8 payload).
* jk/colors:
diff-highlight: do not split multibyte characters
When the input is UTF-8 and Perl is operating on bytes instead of
characters, a diff that changes one multibyte character to another
that shares an initial byte sequence will result in a broken diff
display as the common byte sequence prefix will be separated from
the rest of the bytes in the multibyte character.
For example, if a single line contains only the unicode character
U+C9C4 (encoded as UTF-8 0xEC, 0xA7, 0x84) and that line is then
changed to the unicode character U+C9C0 (encoded as UTF-8 0xEC,
0xA7, 0x80), when operating on bytes diff-highlight will show only
the single byte change from 0x84 to 0x80 thus creating invalid UTF-8
and a broken diff display.
Fix this by putting Perl into character mode when splitting the line
and then back into byte mode after the split is finished.
The utf8::xxx functions require Perl 5.8 so we require that as well.
Also, since we are mucking with code in the split_line function, we
change a '*' quantifier to a '+' quantifier when matching the $COLOR
expression which has the side effect of speeding everything up while
eliminating useless '' elements in the returned array.
Reported-by: Yi EungJun <semtlenori@gmail.com>
Signed-off-by: Kyle J. McKay <mackyle@gmail.com>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
"diff-highlight" filter (in contrib/) allows its color output
to be customized via configuration variables.
* jk/colors:
parse_color: drop COLOR_BACKGROUND macro
diff-highlight: allow configurable colors
parse_color: recognize "no$foo" to clear the $foo attribute
parse_color: support 24-bit RGB values
parse_color: refactor color storage
Until now, the highlighting colors were hard-coded in the
script (as "reverse" and "noreverse"), and you had to edit
the script to change them. This patch teaches diff-highlight
to read from color.diff-highlight.* to set them.
In addition, it expands the possiblities considerably by
adding two features:
1. Old/new lines can be colored independently (so you can
use a color scheme that complements existing line
coloring).
2. Normal, unhighlighted parts of the lines can be colored,
too. Technically this can be done by separately
configuring color.diff.old/new and matching it to your
diff-highlight colors. But you may want a different
look for your highlighted diffs versus your regular
diffs.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
While using diff-highlight with other tools, I have discovered that Python
ignores SIGPIPE by default. Unfortunately, this also means that tools
attempting to launch a pager under Python--and don't realize this is
happening--means that the subprocess inherits this setting. In this case, it
means diff-highlight will be launched with SIGPIPE being ignored. Let's work
with those broken scripts by restoring the default SIGPIPE handler.
Signed-off-by: John Szakmeister <john@szakmeister.net>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The diff-highlight script works on heuristics, so it can be
wrong. Let's document some of the wrong-ness in case
somebody feels like working on it.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Currently we only bother highlighting single-line hunks. The
rationale was that the purpose of highlighting is to point
out small changes between two similar lines that are
otherwise hard to see. However, that meant we missed similar
cases where two lines were changed together, like:
-foo(buf);
-bar(buf);
+foo(obj->buf);
+bar(obj->buf);
Each of those changes is simple, and would benefit from
highlighting (the "obj->" parts in this case).
This patch considers whole hunks at a time. For now, we
consider only the case where the hunk has the same number of
removed and added lines, and assume that the lines from each
segment correspond one-to-one. While this is just a
heuristic, in practice it seems to generate sensible
results (especially because we now omit highlighting on
completely-changed lines, so when our heuristic is wrong, we
tend to avoid highlighting at all).
Based on an original idea and implementation by Michał
Kiedrowicz.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The current code structure assumes that we will only look at
a pair of lines at any given time, and that the end result
should always be to output that pair. However, we want to
eventually handle multi-line hunks, which will involve
collating pairs of removed/added lines. Let's refactor the
code to return highlighted pairs instead of printing them.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
If you have a change like:
-foo
+bar
we end up highlighting the entirety of both lines (since the
whole thing is changed). But the point of diff highlighting
is to pinpoint the specific change in a pair of lines that
are mostly identical. In this case, the highlighting is just
noise, since there is nothing to pinpoint, and we are better
off doing nothing.
The implementation looks for "interesting" pairs by checking
to see whether they actually have a matching prefix or
suffix that does not simply consist of colorization and
whitespace. However, the implementation makes it easy to
plug in other heuristics, too, like:
1. Depending on the source material, the set of "boring"
characters could be tweaked to include language-specific
stuff (like braces or semicolons for C).
2. Instead of saying "an interesting line has at least one
character of prefix or suffix", we could require that
less than N percent of the line be highlighted.
The simple "ignore whitespace, and highlight if there are
any matched characters" implemented by this patch seems to
give good results on git.git. I'll leave experimentation
with other heuristics to somebody who has a dataset that
does not look good with the current code.
Based on an original idea and implementation by Michał
Kiedrowicz.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
These perl features can catch bugs, and we shouldn't be
violating any of the strict rules or creating any warnings,
so let's turn them on.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This is a simple and stupid script for highlighting
differing parts of lines in a unified diff. See the README
for a discussion of the limitations.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
