[shell] provide autocompletion for rql queries in cubicweb-ctl shell (closes #3560541)
Use the ``rql.suggestions`` component to complete user's input
- readline calls the ``complete`` method with user's input,
- the ``complete`` method asks for each known completers if
it can suggest completions for user's input.
[MESSAGES CONTROL]
disable-msg = C0301
[VARIABLES]
# Enable / disable this checker
enable-variables = yes
additional-builtins = _, display_name
[BASIC]
required-attributes=
attr-rgx = (w|[a-z_][a-z0-9_]{2,30})
variable-rgx = (w|[a-z_][a-z0-9_]{2,30})$
argument-rgx = (w|[a-z_][a-z0-9_]{2,30})$
[TYPECHECK]
generated-members=debug,info,notice,warning,error,critical,exception