Detect gsed and use it if it exists

diff-so-fancy

@@ -4,31 +4,33 @@
 
 diff_highlight="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )/third_party/diff-highlight/diff-highlight"
 
+hash gsed 2>/dev/null && SED=gsed || SED=sed
+
 color_code_regex=$'(\x1B\\[([0-9]{1,2}(;[0-9]{1,2})?)[m|K])?'
 reset_color="\x1B\[m"
 dim_magenta="\x1B\[38;05;146m"
 
 format_diff_header () {
 	# simplify the unified patch diff header
-	sed -E "s/^($color_code_regex)diff --git .*$//g" | \
-	sed -E "s/^($color_code_regex)index .*$/\
+	$SED -E "s/^($color_code_regex)diff --git .*$//g" | \
+	$SED -E "s/^($color_code_regex)index .*$/\
 \1$(print_horizontal_rule)/g" | \
-	sed -E "s/^($color_code_regex)\+\+\+(.*)$/\1\+\+\+\5\\
+	$SED -E "s/^($color_code_regex)\+\+\+(.*)$/\1\+\+\+\5\\
 \1$(print_horizontal_rule)/g"
 }
 
 colorize_context_line () {
 	# extra color for @@ context line
-	sed -E "s/@@$reset_color $reset_color(.*$)/@@ $dim_magenta\1/g"
+	$SED -E "s/@@$reset_color $reset_color(.*$)/@@ $dim_magenta\1/g"
 }
 
 strip_leading_symbols () {
 	# strip the + and -
-	sed -E "s/^($color_code_regex)[\+\-]/\1 /g"
+	$SED -E "s/^($color_code_regex)[\+\-]/\1 /g"
 }
 
 print_horizontal_rule () {
-	printf "%$(tput cols)s\n"| sed 's/ /─/g'
+	printf "%$(tput cols)s\n"| $SED 's/ /─/g'
 }
 
 # run it.