Add HIDE_CUSTOM_SUBSTITUTION for customization and add-ons.

Add-ons or users may want to hide parts of the task text from the output.
Though this can already be solved through TODOTXT_FINAL_FILTER, augmenting the configured value is not trivial, and it introduces another SED command into the already long _list() pipeline. Putting an additional HIDE_CUSTOM_SUBSTITUTION into the existing pipeline has hardly any performance implications, and makes the realization of this use case trivial.

tests/t1300-ls.sh

@@ -53,6 +53,18 @@ 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

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