-w does not always default to read parser

[yorickdowne]

Describe the bug

dasel v2.0.2

Run dasel put -f NLog.config -r xml -t json 'nlog.rules.logger' -v '{"-name":"JsonWebAPI.Microsoft.Extensions.Diagnostics.HealthChecks.DefaultHealthCheckService","-maxlevel":"Error","-final":"true"}'

and get

Error: could not get write parser from filename: unknown parser: .config

Expected behavior
Write parser is the same as read parser, instead of taken from filename.

If "from filename" is intended instead, change the --help text.

Additional context
Workaround: Add -w xml and the command works.

[yorickdowne]

NLog.config.txt