diesel_cli compiled features flag

[alexxroche]

Could we add to the version output which features have been compiled into diesel_cli ? I spent two days trying to get diesel to work with postgres, (when it would work with sqlite) and found out that cargo had been failing to re-compile with postgres support.

Ideally:

diesel -V
diesel 1.3.2 "postgres mysql"

or

diesel --version
diesel 1.4.1 "postgres sqlite"

If we need to maintain 100% backwards compatibility then add a new flag

diesel -h
FLAGS:  
    -f, --features
            List which features have been compiled into this version of diesel_cli

diesel -f
postgres sqlite mysql

[weiznich]

This sounds like a great idea. Such a contribution would definitively be welcome.

[alexxroche]

I've sketched out an this idea: #2724
I picked the "maintain backward compatibility", (though obviously the developers of diesel can implement this how they see best.)
Still needs unit_tests for this new feature to ensure that:
cargo build --package diesel_cli --no-default-features --features "sqlite postgres mysql" still works,
and an integration test for ../target/debug/diesel features.