snapcraft.yaml: add support for reload-command and completer directives

[bloodearnest]

reload-command and completer fields are supported in snapd, but not snapcraft

Checklist:

• Have you signed the contributor licence agreement?

Yes, am canonical employee

• Is there a reported a bug for the problem you are fixing?

LP: #1699507

• Have you read our contribution guide?

yes

[bloodearnest]

https://github.com/snapcore/snapd/blob/master/snap/info_snap_yaml.go#L61

https://github.com/snapcore/snapd/blob/master/wrappers/services.go#L205

[elopio]

Thanks @bloodearnest! This looks good to me, but it needs a review from somebody from the snapd team. I see no documentation about reload-command, and last time we did this, we added a value that was supported in snapd but undocumented on purposed because people were not supposed to use it.

@zyga maybe? Want to take a quick look here?

[bloodearnest]

Updated branch to also allow completer directive, for bash completion.

As supported by snapd here:

https://github.com/snapcore/snapd/blob/master/snap/info_snap_yaml.go#L64

[bloodearnest]

Also, the system doesn't seem to know I'm a canonical employee, so It thinks I havn't signed the CLA

[bloodearnest]

Have cleaned up branch to just single commit

[kalikiana]

You have a gmail address in GitHub, that's why the CLA check doesn't recognize you. There's two ways to fix it:

• Sign the CLA with your gmail address
• Change your GitHub email to a Canonical address

[bloodearnest]

Ah, thanks. Have signed as IC.

[sergiusens]

Yeah, I don't see it here https://forum.snapcraft.io/t/the-snap-format/698/2?u=sergiusens

[sergiusens]

please remove this, there is a specific branch adding support for this with user guidance.