Cargo Features

[dependencies]
dir_lines_streamer = { version = "0.2.0", default-features = false, features = ["gz"] }
default = gz

The gz feature is set by default whenever dir_lines_streamer is added without default-features = false somewhere in the dependency tree.

gz default = flate2

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features.

flate2 gz