add watch_exclude setting to _config.yml

[mohkale]

see issue #90

[ashmaroli]

The method :listen_ignore_paths already returns an array of regular expressions. I think it would be better to enhance that method to just convert glob_patterns to regex as well (like the author noted in the issue ticket) instead of requiring a new config option (may result in confusion due to overlap).

[mohkale]

@ashmaroli Understandable, but I don't think it'd be very reliable. What about the annoying edge cases where a person supplies perfectly valid fnmatch arguments, but the regex it produces backtracks and then just hangs forever (I'm not sure whether there's a way to detect and prevent that). Honestly I think jekyll should've made exclude use regexps from the start... but it didn't and now we have to live with the incongruency.

Another, slightly nicer option, would be to add an option to the listen library where it can take a callable for :ignore and then have that callable use fnmatch behind the scenes.

If all that's impossible, then we do still have the option of simply using fnmatch in our listen handler. so in the listen_handler method, we filter out any of the paths in modified, added & removed that match any of our exclude patterns. If all three lists are then empty, exit the method early.

I still think a new config option is the nicest way to do this, but that last approach is the second best :).

[ashmaroli]

I like the second-best option more.. Will you be able to submit a separate PR towards that idea..?

[mohkale]

Yep, I'll submit sometime later today 😄.

Do you want me to remove the watch_exclude config option then?

[ashmaroli]

Lets leave this PR as it is..
The second-best option is to be a separate PR. If that gets accepted by other maintainers, then this PR (and the watch_exclude idea) can be discarded,

[mohkale]

Sorry, got distracted with another project. Anyways see #92.