docs: service create: document non-matching/exclude constraints
@@ -667,7 +667,8 @@ $ docker service create \
### Specify service constraints (--constraint)
You can limit the set of nodes where a task can be scheduled by defining
-constraint expressions. Multiple constraints find nodes that satisfy every
+constraint expressions. Constraint expressions can either use a _match_ (`==`)
+or _exclude_ (`!=`) rule. Multiple constraints find nodes that satisfy every
expression (AND match). Constraints can match node or Docker Engine labels as
follows:
