refactor(reportbug): use awk to extract sources

Author: akinomyoga

completions/reportbug

@@ -42,7 +42,7 @@ _comp_cmd_reportbug()
             ;;
         --from-buildd)
             _comp_compgen_split -S "_" -- "$(apt-cache dumpavail |
-                command grep "^Source: $cur" | sort -u | cut -f2 -d' ')"
+                _comp_awk -F ' ' '$1 == "Source:" && !uniq[$2]++ { print $2 }')"
             return
             ;;
         --smtphost)