deps: Update gocli to v2

Change-Id: da5f7d391e
flag: Fix error message

No need to mention the value, the stdlib flag package does that already.

Change-Id: 86bcd5d344
shell: Add shortcut for exec.Command

Change-Id: 5c444029a5
git: Delete config.go that was forgotten there

No need for this file any more, the config has been rewritten so that
everything is now configurable in the config file.

Change-Id: c15ca09c8d
config: Change local config structure

To make it possible to bootstrap a repository, the custom scripts paths
are from now defined by SalsaFlow, relative to the repository root. This
also means that the relevant local configuration section is no longer
needed.

The new local configuration structure is:

  .salsaflow/
    config.yml
    scripts/
      get_version
      set_version
      ...

Also to make it possible to write scripts that would work across
platforms, a platform suffix can be attached to the script file. For
example, set_version_windows is being used on Windows, set_version_unix
on other operating systems. Naturally, if no platform suffix is
supplied, the same script file is used on all platforms.

Change-Id: 521fca8971
Add a new command: repo bootstrap

This command can be used to generate initial configuration file in the
current repository so that the project can get up to speed with
SalsaFlow quickly.

This basically means that the local configuration file is generated
based on the flags specified. The user then has to check the files and
fill in the missing information.

It is also possible now to use so-called skeletons, which are userful
particularly for custom scripts. Telling repo bootstrap to use
'salsaflow/skeleton-golang' will make SalsaFlow clone the given
repository from GitHub and it will pour the content of the default
branch into .salsaflow directory of the repository. For now it only
makes sense to have the scripts directory there and use the given
skeleton to share these scripts across the same project types.

Change-Id: 05dd968d1a
SalsaFlow: Update the local configuration

Change the local configuration files to keep up with the scripts and
bootstrap changes.

Change-Id: 8078f40c3c