fix(config): add missing user command

[KortanZ]

There is only a user command option in config, this patch register the configed user command to nvim. Tested localy on windows.

[linrongbin16]

I think the dispatcher.update could be auto-triggered when user open a workspace/file, or save the file. So the command is not useful, correct?

In the original idea, I want to use the Gentags command to:

1. Show the generated & cached tags files by this plugin
2. Allow user manual delete these cached tags files
3. Allow user to trigger a GC (garbage collection) on these cached tags files, to avoid too much disk usage.

[KortanZ]

I think the dispatcher.update could be auto-triggered when user open a workspace/file, or save the file. So the command is not useful, correct?

My fault, actuall there is an in progress proposal PR that I've use locally which i add a config option that control whether the auto update is on. My tagfile is relatively large, around 1GiB, and it's really unusable if auto-update happened on every file i opened and modified. I just need a commad to manually trigger the update, and i find the option :-)

In the original idea, I want to use the Gentags command to:
Show the generated & cached tags files by this plugin
Allow user manual delete these cached tags files
Allow user to trigger a GC (garbage collection) on these cached tags files, to avoid too much disk usage.

Now i see. Is it better that we removed the command option and give user a fixed command set, like :GenTags show, :GenTags update?

[linrongbin16]

@KortanZ ,

Now i see. Is it better that we removed the command option and give user a fixed command set, like :GenTags show, :GenTags update?

Yes, it's a great design.

[KortanZ]

Yes, it's a great design.

Great! Now i know how to implement command properly.

Anyway, this PR could close now. Thank you :D