Glob flavor used for event_match is not clear

[jplatte]

Link to problem area: https://matrix.org/docs/spec/client_server/r0.6.1#conditions

Issue

The spec says:

pattern: The glob-style pattern to match against. Patterns with no special glob characters should be treated as having asterisks prepended and appended when testing the condition.

However it doesn't seem like it's specified anywhere what "special glob characters" are, nor what they mean or whether / how they can be escaped. For example * shell globs stop at slashes, but there's often ** as a wildcard that doesn't do that. It also seems like Synapse implements support for [abc], [a-z], [!a-z] as character range wildcards, but not {foo,bar} as "one-of" globs like many / all shells do.

CC #2637
CC ruma/ruma#442 (for the record: current plan is to only support ? and *, without special handling of /)

[turt2live]

#2810 might be suited to fix this

[richvdh]

the C-S API uses globs in three places that I know of: moderation polices, server acls, and push rules. The first two are already specified, so I think the "and others" referred to in the subject is the empty set.