git-range-diff-delta-preproc

#!/usr/bin/env bash

# preprocessor for "git range-diff" output to be fed into "delta" for side-by-side diff
# see ~/.config/git/config for usage (si-range-diff alias)
#
# developed against git 2.40 - git range-diff doesn't have stable output, might need adjustments
# see https://github.com/git/git/blob/ee48e70a829d1fa2da82f14787051ad8e7c45b71/range-diff.c#L376

set -eu

coproc ansi2txt {
	stdbuf -oL ansi2txt
}

while IFS= read -r l; do
	# decolor line for matching/processing
	printf "%s\n" "$l" >&"${ansi2txt[1]}"
	IFS= read -r ll <&"${ansi2txt[0]}"

	if [[ $ll == "    @@ "* ]]; then # hunk header line
		# fake hunk header for delta
		printf "@@ -0,0 +0,0 @@ %s\n" "${ll#    @@ }"
	elif [[ $ll == "    "* ]]; then # hunk diff line
		# un-indent diff
		printf "%s\n" "${ll#    }"
	else # pair header line
		# horizontal separator before the line
		tput setaf 39; tput setab 235; printf %"$(tput cols)"s | sed 's/ /─/g'; tput sgr0
		printf "%s\n" "$l"

		if [[ $ll =~ ^[[:digit:]][[:digit:]]*:"  "([[:alnum:]][[:alnum:]]*)" ! "[[:digit:]][[:digit:]]*:"  "([[:alnum:]][[:alnum:]]*)" " ]]; then
			# fake file header for delta to syntax highlight as patch
			echo "--- ${BASH_REMATCH[1]}.patch"
			echo "+++ ${BASH_REMATCH[2]}.patch"
		else
			# extra line for unmatched commits
			echo
		fi
	fi
done