Optimization: Put grep -v empty task filter inside sed.

No need to spawn off another process for this; we can do this inside the sed command that joins the task numbers with the task text.

tests/t1300-ls.sh

@@ -53,18 +53,6 @@ test_todo_session 'checking TODOTXT_FINAL_FILTER' <<EOF
 TODO: 3 of 3 tasks shown
 EOF
 
-#
-# check the custom hiding
-#
-test_todo_session 'checking HIDE_CUSTOM_SUBSTITUTION' <<EOF
->>> HIDE_CUSTOM_SUBSTITUTION='[tT]h' todo.sh ls
-2 aaa zzz is line should be first.
-3 bbb yyy is line should be second.
-1 ccc xxx is line should be ird.
---
-TODO: 3 of 3 tasks shown
-EOF
-
 #
 # check the filtering of TERM
 #

todo.sh

@@ -775,8 +775,12 @@ _list() {
     fi
     items=$(
         sed = "$src"                                            \
-        | sed "N; s/^/     /; s/ *\(.\{$PADDING,\}\)\n/\1 /"    \
-        | grep -v "^[ 0-9]\+ *$"
+        | sed '''
+            N
+            s/^/     /
+            s/ *\([ 0-9]\{'"$PADDING"',\}\)\n/\1 /
+            /^[ 0-9]\+ *$/d
+         '''
     )
     if [ "${filter_command}" ]; then
         filtered_items=$(echo -n "$items" | eval "${filter_command}")
@@ -812,9 +816,8 @@ _list() {
             }
           '''  \
         | sed '''
-            s/'"${HIDE_PROJECTS_SUBSTITUTION:-^}"'//g
-            s/'"${HIDE_CONTEXTS_SUBSTITUTION:-^}"'//g
-            s/'"${HIDE_CUSTOM_SUBSTITUTION:-^}"'//g
+            s/'${HIDE_PROJECTS_SUBSTITUTION:-^}'//g
+            s/'${HIDE_CONTEXTS_SUBSTITUTION:-^}'//g
           '''                                                   \
         | eval ${TODOTXT_FINAL_FILTER}                          \
     )