Merge branch 'jk/git-tricks'

* jk/git-tricks:
  completion: match ctags symbol names in grep patterns
  contrib: add git-jump script
  contrib: add diff highlight script

5 files changed, 355 insertions, 0 deletions

diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index fc3d0b1a06..98af8f5c7e 100755
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -1430,6 +1430,10 @@ _git_gitk ()
 	_gitk
 }
 
+__git_match_ctag() {
+	awk "/^${1////\\/}/ { print \$1 }" "$2"
+}
+
 _git_grep ()
 {
 	__git_has_doubledash && return
@@ -1452,6 +1456,15 @@ _git_grep ()
 		;;
 	esac
 
+	case "$cword,$prev" in
+	2,*|*,-*)
+		if test -r tags; then
+			__gitcomp "$(__git_match_ctag "$cur" tags)"
+			return
+		fi
+		;;
+	esac
+
 	__gitcomp "$(__git_refs)"
 }
 
diff --git a/contrib/diff-highlight/README b/contrib/diff-highlight/README
new file mode 100644
index 0000000000..1b7b6df8eb
--- /dev/null
+++ b/contrib/diff-highlight/README
@@ -0,0 +1,57 @@
+diff-highlight
+==============
+
+Line oriented diffs are great for reviewing code, because for most
+hunks, you want to see the old and the new segments of code next to each
+other. Sometimes, though, when an old line and a new line are very
+similar, it's hard to immediately see the difference.
+
+You can use "--color-words" to highlight only the changed portions of
+lines. However, this can often be hard to read for code, as it loses
+the line structure, and you end up with oddly formatted bits.
+
+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.
+
+  2. It will find the common prefix and suffix of two lines, and
+     consider everything in the middle to be "different". It could
+     instead do a real diff of the characters between the two lines and
+     find common subsequences. However, the point of the highlight is to
+     call attention to a certain area. Even if some small subset of the
+     highlighted area actually didn't change, that's OK. In practice it
+     ends up being more readable to just have a single blob on the line
+     showing the interesting bit.
+
+The goal of the script is therefore not to be exact about highlighting
+changes, but to call attention to areas of interest without being
+visually distracting.  Non-diff lines and existing diff coloration is
+preserved; the intent is that the output should look exactly the same as
+the input, except for the occasional highlight.
+
+Use
+---
+
+You can try out the diff-highlight program with:
+
+---------------------------------------------
+git log -p --color | /path/to/diff-highlight
+---------------------------------------------
+
+If you want to use it all the time, drop it in your $PATH and put the
+following in your git configuration:
+
+---------------------------------------------
+[pager]
+	log = diff-highlight | less
+	show = diff-highlight | less
+	diff = diff-highlight | less
+---------------------------------------------
diff --git a/contrib/diff-highlight/diff-highlight b/contrib/diff-highlight/diff-highlight
new file mode 100755
index 0000000000..d8938982e4
--- /dev/null
+++ b/contrib/diff-highlight/diff-highlight
@@ -0,0 +1,124 @@
+#!/usr/bin/perl
+
+# Highlight by reversing foreground and background. You could do
+# other things like bold or underline if you prefer.
+my $HIGHLIGHT   = "\x1b[7m";
+my $UNHIGHLIGHT = "\x1b[27m";
+my $COLOR = qr/\x1b\[[0-9;]*m/;
+
+my @window;
+
+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_pair(shift @window, shift @window);
+	}
+	else {
+		print shift @window;
+	}
+
+	# 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;
+	}
+}
+
+# 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_pair(shift @window, shift @window);
+}
+
+# And then flush any remaining lines.
+while (@window) {
+	print shift @window;
+}
+
+exit 0;
+
+sub show_pair {
+	my @a = split_line(shift);
+	my @b = split_line(shift);
+
+	# 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++;
+			$pb++;
+		}
+		else {
+			last;
+		}
+	}
+
+	# Find common suffix, ignoring colors.
+	my ($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;
+		}
+	}
+
+	print highlight(\@a, $pa, $sa);
+	print highlight(\@b, $pb, $sb);
+}
+
+sub split_line {
+	local $_ = shift;
+	return map { /$COLOR/ ? $_ : (split //) }
+	       split /($COLOR*)/;
+}
+
+sub highlight {
+	my ($line, $prefix, $suffix) = @_;
+
+	return join('',
+		@{$line}[0..($prefix-1)],
+		$HIGHLIGHT,
+		@{$line}[$prefix..$suffix],
+		$UNHIGHLIGHT,
+		@{$line}[($suffix+1)..$#$line]
+	);
+}
diff --git a/contrib/git-jump/README b/contrib/git-jump/README
new file mode 100644
index 0000000000..1cebc328cb
--- /dev/null
+++ b/contrib/git-jump/README
@@ -0,0 +1,92 @@
+git-jump
+========
+
+Git-jump is a script for helping you jump to "interesting" parts of your
+project in your editor. It works by outputting a set of interesting
+spots in the "quickfix" format, which editors like vim can use as a
+queue of places to visit (this feature is usually used to jump to errors
+produced by a compiler). For example, given a diff like this:
+
+------------------------------------
+diff --git a/foo.c b/foo.c
+index a655540..5a59044 100644
+--- a/foo.c
++++ b/foo.c
+@@ -1,3 +1,3 @@
+ int main(void) {
+-  printf("hello word!\n");
++  printf("hello world!\n");
+ }
+-----------------------------------
+
+git-jump will feed this to the editor:
+
+-----------------------------------
+foo.c:2: printf("hello word!\n");
+-----------------------------------
+
+Obviously this trivial case isn't that interesting; you could just open
+`foo.c` yourself. But when you have many changes scattered across a
+project, you can use the editor's support to "jump" from point to point.
+
+Git-jump can generate three types of interesting lists:
+
+  1. The beginning of any diff hunks.
+
+  2. The beginning of any merge conflict markers.
+
+  3. Any grep matches.
+
+
+Using git-jump
+--------------
+
+To use it, just drop git-jump in your PATH, and then invoke it like
+this:
+
+--------------------------------------------------
+# jump to changes not yet staged for commit
+git jump diff
+
+# jump to changes that are staged for commit; you can give
+# arbitrary diff options
+git jump diff --cached
+
+# jump to merge conflicts
+git jump merge
+
+# jump to all instances of foo_bar
+git jump grep foo_bar
+
+# same as above, but case-insensitive; you can give
+# arbitrary grep options
+git jump grep -i foo_bar
+--------------------------------------------------
+
+
+Related Programs
+----------------
+
+You can accomplish some of the same things with individual tools. For
+example, you can use `git mergetool` to start vimdiff on each unmerged
+file. `git jump merge` is for the vim-wielding luddite who just wants to
+jump straight to the conflict text with no fanfare.
+
+As of git v1.7.2, `git grep` knows the `--open-files-in-pager` option,
+which does something similar to `git jump grep`. However, it is limited
+to positioning the cursor to the correct line in only the first file,
+leaving you to locate subsequent hits in that file or other files using
+the editor or pager. By contrast, git-jump provides the editor with a
+complete list of files and line numbers for each match.
+
+
+Limitations
+-----------
+
+This scripts was written and tested with vim. Given that the quickfix
+format is the same as what gcc produces, I expect emacs users have a
+similar feature for iterating through the list, but I know nothing about
+how to activate it.
+
+The shell snippets to generate the quickfix lines will almost certainly
+choke on filenames with exotic characters (like newlines).
diff --git a/contrib/git-jump/git-jump b/contrib/git-jump/git-jump
new file mode 100755
index 0000000000..a33674e47a
--- /dev/null
+++ b/contrib/git-jump/git-jump
@@ -0,0 +1,69 @@
+#!/bin/sh
+
+usage() {
+	cat <<\EOF
+usage: git jump <mode> [<args>]
+
+Jump to interesting elements in an editor.
+The <mode> parameter is one of:
+
+diff: elements are diff hunks. Arguments are given to diff.
+
+merge: elements are merge conflicts. Arguments are ignored.
+
+grep: elements are grep hits. Arguments are given to grep.
+EOF
+}
+
+open_editor() {
+	editor=`git var GIT_EDITOR`
+	eval "$editor -q \$1"
+}
+
+mode_diff() {
+	git diff --relative "$@" |
+	perl -ne '
+	if (m{^\+\+\+ b/(.*)}) { $file = $1; next }
+	defined($file) or next;
+	if (m/^@@ .*\+(\d+)/) { $line = $1; next }
+	defined($line) or next;
+	if (/^ /) { $line++; next }
+	if (/^[-+]\s*(.*)/) {
+		print "$file:$line: $1\n";
+		$line = undef;
+	}
+	'
+}
+
+mode_merge() {
+	git ls-files -u |
+	perl -pe 's/^.*?\t//' |
+	sort -u |
+	while IFS= read fn; do
+		grep -Hn '^<<<<<<<' "$fn"
+	done
+}
+
+# Grep -n generates nice quickfix-looking lines by itself,
+# but let's clean up extra whitespace, so they look better if the
+# editor shows them to us in the status bar.
+mode_grep() {
+	git grep -n "$@" |
+	perl -pe '
+	s/[ \t]+/ /g;
+	s/^ *//;
+	'
+}
+
+if test $# -lt 1; then
+	usage >&2
+	exit 1
+fi
+mode=$1; shift
+
+trap 'rm -f "$tmp"' 0 1 2 3 15
+tmp=`mktemp -t git-jump.XXXXXX` || exit 1
+type "mode_$mode" >/dev/null 2>&1 || { usage >&2; exit 1; }
+"mode_$mode" "$@" >"$tmp"
+test -s "$tmp" || exit 0
+open_editor "$tmp"