Rework script to address review comments

Author: fanninpm

scripts/whats_left_builtin_items.sh

@@ -1,12 +1,29 @@
 #!/bin/bash
+set -euo pipefail
 
 # create directory if it doesn't exist
 mkdir -p ../_data/whats_left
 
-# start a new csv file for builtin items
-echo "builtin,name,is_inherited" > ../_data/whats_left/builtin_items.csv
+# exit violently if the temp file does not exist
+if [ ! -f ../_data/whats_left.temp ]; then
+    exit 1
+fi
 
-# read the temp file
-# in awk:
-sed -n '/# builtin items/{n;:a;/^$/q;p;n;ba;}' ../_data/whats_left.temp | \
-awk -v OFS=',' '{split($1,a,".");if(index($0,FS)>0){b=substr($0,index($0,FS)+1)}else{b=""};print a[1],$1,b}' >> ../_data/whats_left/builtin_items.csv
+# generate the CSV file for builtin items from the temp file
+awk -f - ../_data/whats_left.temp > ../_data/whats_left/builtin_items.csv <<'EOF'
+BEGIN {
+    OFS=","
+    print "builtin,name,is_inherited"
+}
+/^# builtin items/ { in_section=1; next }
+/^$/ { if (in_section) exit }
+in_section {
+    split($1, a, ".")
+    rest = ""
+    idx = index($0, " ")
+    if (idx > 0) {
+        rest = substr($0, idx+1)
+    }
+    print a[1], $1, rest
+}
+EOF