Add a command to update the application.

[kherge]

Problem

As Sqon reaches a stable release, developers will need a way to update the Sqon application without having to manually download and reinstall the application from the Releases page.

Resolution

I would like to be able to run sqon self-update to update the Sqon application.

Process

The self-update command would process an update in the following manner:

1. Download the release manifest from the Sqon application project website over HTTPS.
2. Find an appropriate release.
   1. If --patch is used, only the next patch release will be searched for.
   2. If --minor is used, only the next minor release will be searched for.
   3. If --major is used, only the next major release will be searched for.
   4. If no option is used, any next available release will be searched for.
3. If a new release is available, continue.
   • If a new release is not available, alert the user and stop here.
4. The new release and its GPG signature are downloaded to a temporary location. This temporary location can be changed by specifying the --temp option. Download progress can be displayed as a progress bar.
5. The GPG signature is verified.
   • If GPG is not available, a warning is reported and the user will be prompted to confirm that it is okay to skip the verification step.
     • The --no-verification option can be used to skip this step.
     • If the --no-interaction option is used, the prompt will always deny continuing without verification unless the --no-verification option is used.
6. The current installation is replaced by the new release.

An --unstable option can be used to modify the other available options.

References

1. https://github.com/composer/composer/blob/master/src/Composer/Command/SelfUpdateCommand.php
2. https://github.com/box-project/amend/blob/master/src/lib/KevinGH/Amend/Command.php
3. http://semver.org/spec/v2.0.0.html