Use pygmentize for git diffs

.gitconfig

@@ -27,6 +27,7 @@
 	rebase = true
 [diff]
 	tool = meld
+	external = git-hldiff-driver
 [difftool]
 	prompt = false
 [difftool "meld"]

git-hldiff-driver

+#!/bin/bash
+set -euo pipefail
+
+# Program suitable for GIT_EXTERNAL_DIFF, which will syntax-highlight differences.
+
+hldiff -u "$2" "$5" || true

hldiff

+#!/bin/bash
+set -euo pipefail
+
+# Diff two files with syntax highlighting using pygmentize.
+
+# pygmentize should be a pygmentize wrapper with your preferred
+# pygmentize settings (formatter / style / filters)
+
+function prepare() {
+    local fn=$1
+
+    # Work around https://bitbucket.org/birkenfeld/pygments-main/issues/1437
+    if [[ "$fn" == /dev/null ]]
+    then
+        return
+    fi
+
+    local lexer
+    lexer=$(pygmentize -N "$fn")
+    #printf "Detected lexer of %q as %q\n" "$fn" "$lexer" 1>&2
+
+    if [[ "$lexer" == text ]]
+    then
+        expand "$fn" | pygmentize-term -g
+    else
+        expand "$fn" | pygmentize-term -l "$lexer"
+    fi
+}
+
+# Use colordiff (instead of diff --color=always) solely because it
+# produces consistent formatting on a per-line basis, saving us from
+# having to keep track of state across lines
+diff=(colordiff --color=yes)
+
+for arg in "$@"
+do
+    if [[ $arg == -* ]]
+    then
+        diff+=("$arg")
+    else
+        exec {fd}< <(prepare "$arg")
+        diff+=(/dev/fd/$fd)
+    fi
+done
+
+sed=(
+    sed
+    # replace "all attributes off" (used by Pygmentize to turn off
+    # bold) with "normal intensity"
+    -e 's/\x1b\[00m/\x1b[22m/g'
+
+    # Replace colordiff's foreground colors with some dark background
+    # colors. You can customize them here.
+    -e 's/^\x1b\[0;36m/\x1b[0;36;48;5;23m/' # cyan
+    -e 's/^\x1b\[0;31m/\x1b[0;31;48;5;52m/' # red
+    -e 's/^\x1b\[0;32m/\x1b[0;32;48;5;22m/' # green
+
+    # Extend background color across the entire terminal window width
+    -e 's/\x1b\[0;0m$/\x1b\[K\x1b[0m/'
+)
+
+"${diff[@]}" | "${sed[@]}"

pygmentize-term

+#!/bin/sh
+exec pygmentize -f terminal256 -O bg=dark,style=monokai "$@"