Build configurations, schemes and xcconfig: how to separate Debug, Staging and Release?

Middle PRO

Essence

Build configuration — a set of build setting values: Debug (no optimizations, DEBUG in compilation conditions, convenient debugging) and Release (optimizations, dSYM, no debug code). You can add as many as you like, for example Staging.
Scheme — what to build and with which configuration for each action: Run, Test, Profile, Analyze, Archive. By default Run and Test use Debug, Profile and Archive use Release. A scheme for CI is marked Shared so it lives in xcshareddata in the repository.
Target — a product (app, extension, tests) with its own build settings.

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