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path: root/contrib/diff-highlight/DiffHighlight.pm
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2026-03-23diff-highlight: fetch all config with one processJeff King
When diff-highlight was written, there was no way to fetch multiple config keys _and_ have them interpreted as colors. So we were stuck with either invoking git-config once for each config key, or fetching them all and converting human-readable color names into ANSI codes ourselves. I chose the former, but it means that diff-highlight kicks off 6 git-config processes (even if you haven't configured anything, it has to check each one). But since Git 2.18.0, we can do: git config --type=color --get-regexp=^color\.diff-highlight\. to get all of them in one shot. Note that any callers which pass in colors directly to the module via @OLD_HIGHLIGHT and @NEW_HIGHLIGHT (like diff-so-fancy plans to do) are unaffected; those colors suppress any config lookup we'd do ourselves. You can see the effect like: # diff-highlight suppresses git-config's stderr, so dump # trace through descriptor 3 git show d1f33c753d | GIT_TRACE=3 diff-highlight 3>&2 >/dev/null which drops from 6 lines down to 1. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2026-03-23diff-highlight: allow module callers to pass in color configScott Baker
Users of the module may want to pass in their own color config for a few obvious reasons: - they are pulling the config from different variables than diff-highlight itself uses - they are loading the config in a more efficient way (say, by parsing git-config --list) and don't want to incur the six (!) git-config calls that DiffHighlight.pm runs to check all config Let's allow users of the module to pass in the color config, and lazy-load it when needed if they haven't. Signed-off-by: Scott Baker <scott@perturb.org> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2026-03-23diff-highlight: drop perl version dependency back to 5.8Scott Baker
The diff-highlight code does not rely on any perl features beyond what perl 5.8 provides. We bumped it to v5.26 along with the rest of the project's perl scripts in 702d8c1f3b (Require Perl 5.26.0, 2024-10-23). There's some value in just having a uniform baseline for the project, but I think diff-highlight is special here: - it's in a contrib/ directory that is not frequently touched, so there is little risk of Git developers getting annoyed that modern perl features are not available - it provides a module used by other projects. In particular, diff-so-fancy relies on DiffHighlight.pm but does not otherwise require a perl version more modern than 5.8. Let's drop back to the more conservative requirement. Signed-off-by: Scott Baker <scott@perturb.org> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2026-03-19contrib/diff-highlight: do not highlight identical pairsJeff King
We pair lines for highlighting based on their position in the hunk. So we should never see two identical lines paired, like: -one -two +one +something else which would pair -one/+one, because that implies that the diff could easily be shrunk by turning line "one" into context. But there is (at least) one exception: removing a newline at the end of a file will produce a diff like: -foo +foo \No newline at end of file And we will pair those two lines. As a result, we end up marking the whole line, including the newline, as the shared prefix. And there's an empty suffix. The most obvious bug here is that when we try to print the highlighted lines, we remove the trailing newline from the suffix, but do not bother with the prefix (under the assumption that there had to be a difference _somewhere_ in the line, and thus the prefix would not eat all the way up to the newline). And so you get an extra line like: -foo +foo \No newline at end of file This is obviously ugly, but also causes interactive.diffFilter to (rightly) complain that the input and output do not match their lines 1-to-1. This could easily be fixed by chomping the prefix, too, but I think the problem is deeper. For one, I suspect some of the other logic gets confused by forming an array with zero-indexed element "3" in a 3-element array. But more importantly, we try not to highlight whole lines, as there's nothing interesting to show there. So let's catch this early in is_pair_interesting() and bail to our usual passthrough strategy. Reported-by: Scott Baker <scott@perturb.org> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-10-23Require Perl 5.26.0brian m. carlson
Our platform support policy states that we require "versions of dependencies which are generally accepted as stable and supportable, e.g., in line with the version used by other long-term-support distributions". Of Debian, Ubuntu, RHEL, and SLES, the four most common distributions that provide LTS versions, the version with mainstream long-term security support with the oldest Perl is 5.26.0 in SLES 15.6. This is a major upgrade, since Perl 5.8.1, according to the Perl documentation, was released in September of 2003. It brings a lot of new features that we can choose to use, such as s///r to return the modified string, the postderef functionality, and subroutine signatures, although the latter was still considered experimental until 5.36. This change was made with the following one-liner, which intentionally excludes modifying the vendored modules we include to avoid conflicts: git grep -l 'use 5.008001' | grep -v 'LoadCPAN/' | xargs perl -pi -e 's/use 5.008001/require v5.26/' Use require instead of use to avoid changing the behavior as the latter enables features and the former does not. Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Taylor Blau <me@ttaylorr.com>
2023-11-17perl: bump the required Perl version to 5.8.1 from 5.8.0Todd Zullinger
The following commit will make use of a Getopt::Long feature which is only present in Perl >= 5.8.1. Document that as the minimum version we support. Many of our Perl scripts will continue to run with 5.8.0 but this change allows us to adjust them as needed without breaking any promises to our users. The Perl requirement was last changed in d48b284183 (perl: bump the required Perl version to 5.8 from 5.6.[21], 2010-09-24). At that time, 5.8.0 was 8 years old. It is now over 21 years old. Signed-off-by: Todd Zullinger <tmz@pobox.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-21diff-highlight: correctly match blank lines for flushJeff King
We try to flush the output from diff-highlight whenever we see a blank line. That lets you see the output for each commit as soon as it is generated, even if Git is still chugging away at a diff, or traversing to find the next commit. However, our "blank line" match checks length($_). That won't ever be true, because we haven't chomped the line ending. As a result, we never flush. Instead, let's use a simple regex which handles line endings in with the end-of-line marker. This has been broken since the initial version in 927a13fe87 (contrib: add diff highlight script, 2011-10-18). Probably nobody noticed because: - most output is big enough, or comes fast enough, that it flushes anyway. And it can be difficult to notice the difference between "show a commit, then pause" and "pause, then show two commits". I only noticed because I was viewing "git log" output on a repo with a very slow textconv filter. - if stdout is going to the terminal (and not another pager like less), then the flush isn't necessary. So any manual testing would show it appearing to work. You can easily see the difference with something like: echo '* diff=slow' >>.gitattributes git -c diff.slow.textconv='sleep 1; cat' \ -c pager.log='diff-highlight | less' \ log -p That should generate one commit every second or so (more if it touches multiple files), but without this patch it waits for many seconds before generating several pages of output. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-15diff-highlight: fix a whitespace nitNorman Rasmussen
This changes the indent from "<tab><sp><sp><sp><sp><sp><sp><sp><sp>" to "<tab><tab>" so that the statement lines up with the rest of the block. Signed-off-by: Norman Rasmussen <norman@rasmussen.co.za> Acked-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-05-09diff-highlight: use correct /dev/null for UNIX and WindowsChris. Webster
Use File::Spec->devnull() for output redirection to avoid messages when Windows version of Perl is first in path. The message 'The system cannot find the path specified.' is displayed each time git is run to get colors. Signed-off-by: Chris. Webster <chris@webstech.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-03-21diff-highlight: detect --graph by indentJeff King
This patch fixes a corner case where diff-highlight may scramble some diffs when combined with --graph. Commit 7e4ffb4c17 (diff-highlight: add support for --graph output, 2016-08-29) taught diff-highlight to skip past the graph characters at the start of each line with this regex: ($COLOR?\|$COLOR?\s+)* I.e., any series of pipes separated by and followed by arbitrary whitespace. We need to match more than just a single space because the commit in question may be indented to accommodate other parts of the graph drawing. E.g.: * commit 1234abcd | ... | diff --git ... has only a single space, but for the last commit before a fork: | | | | * | commit 1234abcd | |/ ... | | diff --git the diff lines have more spaces between the pipes and the start of the diff. However, when we soak up all of those spaces with the $GRAPH regex, we may accidentally include the leading space for a context line. That means we may consider the actual contents of a context line as part of the diff syntax. In other words, something like this: normal context line -old line +new line -this is a context line with a leading dash would cause us to see that final context line as a removal line, and we'd end up showing the hunk in the wrong order: normal context line -old line -this is a context line with a leading dash +new line Instead, let's a be a little more clever about parsing the graph. We'll look for the actual "*" line that marks the start of a commit, and record the indentation we see there. Then we can skip past that indentation when checking whether the line is a hunk header, removal, addition, etc. There is one tricky thing: the indentation in bytes may be different for various lines of the graph due to coloring. E.g., the "*" on a commit line is generally shown without color, but on the actual diff lines, it will be replaced with a colorized "|" character, adding several bytes. We work around this here by counting "visible" bytes. This is unfortunately a bit more expensive, making us about twice as slow to handle --graph output. But since this is meant to be used interactively anyway, it's tolerably fast (and the non-graph case is unaffected). One alternative would be to search for hunk header lines and use their indentation (since they'd have the same colors as the diff lines which follow). But that just opens up different corner cases. If we see: | | @@ 1,2 1,3 @@ we cannot know if this is a real diff that has been indented due to the graph, or if it's a context line that happens to look like a diff header. We can only be sure of the indent on the "*" lines, since we know those don't contain arbitrary data (technically the user could include a bunch of extra indentation via --format, but that's rare enough to disregard). Reported-by: Phillip Wood <phillip.wood@dunelm.org.uk> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-03-21diff-highlight: use flush() helper consistentlyJeff King
The current flush() helper only shows the queued diff but does not clear the queue. This is conceptually a bug, but it works because we only call it once at the end of the program. Let's teach it to clear the queue, which will let us use it in more places (one for now, but more in future patches). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-15diff-highlight: split code into moduleJeff King
The diff-so-fancy project is also written in perl, and most of its users pipe diffs through both diff-highlight and diff-so-fancy. It would be nice if this could be done in a single script. So let's pull most of diff-highlight's code into its own module which can be used by diff-so-fancy. In addition, we'll abstract a few basic items like reading from stdio so that a script using the module can do more processing before or after diff-highlight handles the lines. See the README update for more details. One small downside is that the diff-highlight script must now be built using the Makefile. There are ways around this, but it quickly gets into perl arcana. Let's go with the simple solution. As a bonus, our Makefile now respects the PERL_PATH variable if it is set. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>