The `--robot` option of the CLI causes the program to output
machine-parseable strings, which can be easily consumed by the GUI to
update progress and other information.
The problem is that if the CLI fails to parse its command line arguments
when being called from the GUI for whatever reason, the `.fail()` Yargs
handler will be called, which doesn't output error information in the
usual "robot" format, causing the GUI to not understand the error
message.
Since the `.fail()` Yargs handler doesn't have access to the passed
options, we moved the "robot" functionality to an environment variable,
which we can easily check from there.
As a bonus, this PR refactors the whole robot logic into
`lib/shared/robot.js` and adds unit tests to it.
See: https://github.com/resin-io/etcher/issues/986
Change-Type: major
Changelog-Entry: Replace the `--robot` CLI option with an `ETCHER_CLI_ROBOT` environment variable.
Signed-off-by: Juan Cruz Viotti <jviotti@openmailbox.org>
