generate-cmds.sh: factor out synopsis extract code

This makes it easier to reuse the same code in another place (very
soon).

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

generate-cmdlist.sh

@@ -1,5 +1,15 @@
 #!/bin/sh
 
+get_synopsis () {
+	sed -n '
+		/^NAME/,/'"$1"'/H
+		${
+			x
+			s/.*'"$1"' - \(.*\)/N_("\1")/
+			p
+		}' "Documentation/$1.txt"
+}
+
 echo "/* Automatically generated by generate-cmdlist.sh */
 struct cmdname_help {
 	char name[16];
@@ -39,12 +49,6 @@ sort |
 while read cmd tags
 do
 	tag=$(echo "$tags" | sed "$substnum; s/[^0-9]//g")
-	sed -n '
+	echo "	{\"$cmd\", $(get_synopsis git-$cmd), $tag},"
-		/^NAME/,/git-'"$cmd"'/H
-		${
-			x
-			s/.*git-'"$cmd"' - \(.*\)/	{"'"$cmd"'", N_("\1"), '$tag'},/
-			p
-		}' "Documentation/git-$cmd.txt"
 done
 echo "};"