Provide a /packit help comment command

[lachmanfrantisek]

I've seen an occurrence of /packit help comment command and found it interesting -- can't we provide a nice help message?

Implementation:

• Create a new handler for /packit help command.
• React in form of a comment and provide:
  • A list of relevant/all commands Packit supports.
  • Relevant links to the documentation.
  • Contact / or a link to contact.

[TomasTomecek]

Now that we have more than just /packit build this makes a ton of sense.

[nforro]

Still relevant.

[ptoscano]

Personal idea: in addition to this, I'd like to see the commands documented in a single page (preferably). My reasons for this are two:

• having a command reference available in a single page, easy to read and to search for commands
• not having to request for help directly in PRs/MRs, and thus less "pollution" with help commands and their outputs

[Gauravpadam]

Can I help here?

[lsm5]

coming here from a recent matrix thread, thanks @nforro .

RE: Fedora dist-git in particular, since there are both /packit and /packit-ci commands usable there, it'd be nice for the help subcommand to suggest checking out the other command.

For example, on this dist-git PR, I tried /packit test and kept wondering why it didn't work, only to find out later it was /packit-ci test. Some kind of suggestion or default help message on not recognizing the subcommand could be really helpful in such cases.