pri: Check for existing priority and adapt message.

The existing check (as with depri) didn't do much good. Instead, fetch the existing priority and use that information to print more specific messages:
- TODO: 42 re-prioritized from (C) to (A)
- TODO: 42 already prioritized (A)

tests/t1200-pri.sh

@@ -53,9 +53,28 @@ TODO: 2 prioritized (C).
 --
 TODO: 3 of 3 tasks shown
 
+>>> todo.sh add "smell the coffee +wakeup"
+4 smell the coffee +wakeup
+TODO: 4 added.
+
+>>> todo.sh -p list
+1 (B) smell the uppercase Roses +flowers @outside
+2 (C) notice the sunflowers
+4 smell the coffee +wakeup
+3 stop
+--
+TODO: 4 of 4 tasks shown
+EOF
+
+cat > todo.txt <<EOF
+(B) smell the uppercase Roses +flowers @outside
+(C) notice the sunflowers
+stop
+EOF
+test_todo_session 'reprioritize' <<EOF
 >>> todo.sh pri 2 A
 2 (A) notice the sunflowers
-TODO: 2 prioritized (A).
+TODO: 2 re-prioritized from (C) to (A).
 
 >>> todo.sh -p list
 2 (A) notice the sunflowers
@@ -66,25 +85,12 @@ TODO: 3 of 3 tasks shown
 
 >>> todo.sh pri 2 a
 2 (A) notice the sunflowers
-TODO: 2 prioritized (A).
+TODO: 2 already prioritized (A).
 
 >>> todo.sh -p listpri
 2 (A) notice the sunflowers
 1 (B) smell the uppercase Roses +flowers @outside
 --
 TODO: 2 of 3 tasks shown
-
->>> todo.sh add "smell the coffee +wakeup"
-4 smell the coffee +wakeup
-TODO: 4 added.
-
->>> todo.sh -p list
-2 (A) notice the sunflowers
-1 (B) smell the uppercase Roses +flowers @outside
-4 smell the coffee +wakeup
-3 stop
---
-TODO: 4 of 4 tasks shown
 EOF
-
 test_done

tests/t1500-do.sh

@@ -81,6 +81,6 @@ test_todo_session 'fail multiple do attempts' <<EOF
 TODO: 3 marked as done.
 
 >>> todo.sh -a do 3
-3 is already marked done
+TODO: 3 is already marked done.
 EOF
 test_done

tests/t1700-depri.sh

@@ -68,4 +68,30 @@ TODO: 2 deprioritized.
 TODO: 3 of 3 tasks shown
 EOF
 
+cat > todo.txt <<EOF
+(B) smell the uppercase Roses +flowers @outside
+(A) notice the sunflowers
+stop
+EOF
+test_todo_session 'depriority of unprioritized task' <<EOF
+>>> todo.sh -p list
+2 (A) notice the sunflowers
+1 (B) smell the uppercase Roses +flowers @outside
+3 stop
+--
+TODO: 3 of 3 tasks shown
+
+>>> todo.sh depri 3 2
+TODO: 3 is not prioritized.
+2 notice the sunflowers
+TODO: 2 deprioritized.
+
+>>> todo.sh -p list
+1 (B) smell the uppercase Roses +flowers @outside
+2 notice the sunflowers
+3 stop
+--
+TODO: 3 of 3 tasks shown
+EOF
+
 test_done

todo.sh

@@ -921,10 +921,7 @@ case $action in
 	todo=$(sed "$item!d" "$TODO_FILE")
 	[ -z "$todo" ] && die "TODO: No task $item."
 
-	sed -e $item"s/^(.) //" "$TODO_FILE" > /dev/null 2>&1
-
-	if [ "$?" -eq 0 ]; then
-	    #it's all good, continue
+	if sed "$item!d" "$TODO_FILE" | grep "^(.) " > /dev/null; then
 	    sed -i.bak -e $item"s/^(.) //" "$TODO_FILE"
 	    if [ $TODOTXT_VERBOSE -gt 0 ]; then
 		NEWTODO=$(sed "$item!d" "$TODO_FILE")
@@ -932,7 +929,7 @@ case $action in
 		echo "TODO: $item deprioritized."
 	    fi
 	else
-	    die "$errmsg"
+	    echo "TODO: $item is not prioritized."
 	fi
     done
     ;;
@@ -964,7 +961,7 @@ case $action in
                 echo "TODO: $item marked as done."
 	    fi
         else
-            echo "$item is already marked done"
+            echo "TODO: $item is already marked done."
         fi
     done
 
@@ -1089,18 +1086,23 @@ note: PRIORITY must be anywhere from A to Z."
     [[ "$item" = +([0-9]) ]] || die "$errmsg"
     [[ "$newpri" = @([A-Z]) ]] || die "$errmsg"
 
-    sed -e $item"s/^(.) //" -e $item"s/^/($newpri) /" "$TODO_FILE" > /dev/null 2>&1
-
-    if [ "$?" -eq 0 ]; then
-        #it's all good, continue
+    oldpri=$(sed -ne $item's/^(\(.\)) .*/\1/p' "$TODO_FILE")
+    if [ "$oldpri" != "$newpri" ]; then
         sed -i.bak -e $item"s/^(.) //" -e $item"s/^/($newpri) /" "$TODO_FILE"
-        if [ $TODOTXT_VERBOSE -gt 0 ]; then
-            NEWTODO=$(sed "$item!d" "$TODO_FILE")
-            echo "$item $NEWTODO"
-            echo "TODO: $item prioritized ($newpri)."
-	fi
-    else
-        die "$errmsg"
+    fi
+    if [ $TODOTXT_VERBOSE -gt 0 ]; then
+        NEWTODO=$(sed "$item!d" "$TODO_FILE")
+        echo "$item $NEWTODO"
+        if [ "$oldpri" != "$newpri" ]; then
+            if [ "$oldpri" ]; then
+                echo "TODO: $item re-prioritized from ($oldpri) to ($newpri)."
+            else
+                echo "TODO: $item prioritized ($newpri)."
+            fi
+        fi
+    fi
+    if [ "$oldpri" = "$newpri" ]; then
+        echo "TODO: $item already prioritized ($newpri)."
     fi
     ;;