ENH: Better completion for custom add-ons via new listaddons command.

The todo_completion had the problem that it didn't consider the todo.cfg itself for the location of TODO_ACTIONS_DIR, it just tried the default location or a globally exported config value. With the injection of custom configuration now in place, we can actually delegate the listing to todo.sh itself.
The added built-in "listaddons" command is used for that; it may also be helpful for troubleshooting or to find out about available add-ons. (But the help / shorthelp commands offer more information.)

Additionally, completion is now more precise; only executable actions and no subdirs are listed now; this is also covered by the enhanced test.

The last bonus: The custom add-on actions are now only determined when there's actually completion of commands.

.gitignore

@@ -1,6 +1,3 @@
 VERSION-FILE
 tests/test-results
 tests/trash\ directory.*
-done.txt
-report.txt
-todo.txt

tests/t1310-listcon.sh

@@ -55,16 +55,6 @@ test_todo_session 'listcon e-mail address test' <<EOF
 @con02
 EOF
 
-cat > todo.txt <<EOF
-(B) smell the uppercase Roses +roses @outside +shared
-(C) notice the sunflowers +sunflowers @garden +shared +landscape
-stop
-EOF
-test_todo_session 'listcon with project' <<EOF
->>> todo.sh listcon +landscape
-@garden
-EOF
-
 cat > todo.txt <<EOF
 @con01 -- Some context 1 task
 EOF

todo.sh

@@ -58,7 +58,7 @@ shorthelp()
 		    list|ls [TERM...]
 		    listall|lsa [TERM...]
 		    listaddons
-		    listcon|lsc [TERM...]
+		    listcon|lsc
 		    listfile|lf [SRC [TERM...]]
 		    listpri|lsp [PRIORITIES] [TERM...]
 		    listproj|lsprj [TERM...]
@@ -223,10 +223,9 @@ help()
 		    listaddons
 		      Lists all added and overridden actions in the actions directory.
 
-		    listcon [TERM...]
-		    lsc [TERM...]
+		    listcon
+		    lsc
 		      Lists all the task contexts that start with the @ sign in todo.txt.
-		      If TERM specified, considers only tasks that contain TERM(s).
 
 		    listfile [SRC [TERM...]]
 		    lf [SRC [TERM...]]
@@ -246,11 +245,10 @@ help()
 		      Hides all tasks that contain TERM(s) preceded by a minus sign
 		      (i.e. -TERM).  
 
-		    listproj [TERM...]
-		    lsprj [TERM...]
+		    listproj
+		    lsprj
 		      Lists all the projects (terms that start with a + sign) in
 		      todo.txt.
-		      If TERM specified, considers only tasks that contain TERM(s).
 
 		    move ITEM# DEST [SRC]
 		    mv ITEM# DEST [SRC]
@@ -860,17 +858,7 @@ _format()
     fi
 }
 
-listWordsWithSigil()
-{
-    sigil=$1
-    shift
-
-    FILE=$TODO_FILE
-    [ "$TODOTXT_SOURCEVAR" ] && eval "FILE=$TODOTXT_SOURCEVAR"
-    eval "$(filtercommand 'cat "${FILE[@]}"' '' "$@")" | grep -o "[^ ]*${sigil}[^ ]\\+" | grep "^$sigil" | sort -u
-}
-
-export -f cleaninput getPrefix getTodo getNewtodo shellquote filtercommand _list listWordsWithSigil getPadding _format die
+export -f cleaninput getPrefix getTodo getNewtodo shellquote filtercommand _list getPadding _format die
 
 # == HANDLE ACTION ==
 action=$( printf "%s\n" "$ACTION" | tr 'A-Z' 'a-z' )
@@ -1145,13 +1133,16 @@ case $action in
     ;;
 
 "listcon" | "lsc" )
-    shift
-    listWordsWithSigil '@' "$@"
+    FILE=$TODO_FILE
+    [ "$TODOTXT_SOURCEVAR" ] && eval "FILE=$TODOTXT_SOURCEVAR"
+    grep -ho '[^ ]*@[^ ]\+' "${FILE[@]}" | grep '^@' | sort -u
     ;;
 
 "listproj" | "lsprj" )
+    FILE=$TODO_FILE
+    [ "$TODOTXT_SOURCEVAR" ] && eval "FILE=$TODOTXT_SOURCEVAR"
     shift
-    listWordsWithSigil '+' "$@"
+    eval "$(filtercommand 'cat "${FILE[@]}"' '' "$@")" | grep -o '[^ ]*+[^ ]\+' | grep '^+' | sort -u
     ;;
 
 "listpri" | "lsp" )

todo_completion

@@ -58,7 +58,7 @@ _todo()
                             # a safety check of the ls action output.
                             local todo=$( \
                                 eval TODOTXT_VERBOSE=0 $_todo_sh '-@ -+ -p -x command ls "^ *${cur} "' | \
-                                sed -e 's/^ *[0-9]\{1,\} //' -e 's/\((.) \)[0-9]\{2,4\}-[0-9]\{2\}-[0-9]\{2\} /\1/' \
+                                sed -e 's/^ *[0-9]\+ //' -e 's/\((.) \)[0-9]\{2,4\}-[0-9]\{2\}-[0-9]\{2\} /\1/' \
                                     -e 's/\([xX] \)\([0-9]\{2,4\}-[0-9]\{2\}-[0-9]\{2\} \)\{1,2\}/\1/' \
                                     -e 's/[[:space:]]*$//' \
                                     -e '1q' \