Logger plugin has been improved with many new features:

• command /logger (to see log status for open buffers, and set/disable log level on a buffer)
• custom level by buffer (or group of buffers)
• custom log filename mask by buffer (or group of buffers).

Set one directory by IRC server and a file by channel inside:

Do that: /set logger.mask.irc irc/$server/$channel.weechatlog

You'll have a tree like that:

~/.weechat/
    |- logs/
        |- irc/
            |--- freenode/
            |       freenode.weechatlog
            |       #weechat.weechatlog
            |       #mychan.weechatlog
            |--- oftc/
            |       oftc.weechatlog
            |       #chan1.weechatlog
            |       #chan2.weechatlog

Log all messages on IRC buffers but not join/part/quit messages:

• for all IRC buffers: /set logger.level.irc 3
• for a server and its channels: /set logger.level.irc.freenode 3
• for a specific channel: /set logger.level.irc.freenode.#weechat 3