feat: support package builders to allow configuring certain C dependencies

Namely, `zlib` and sha1 hashing.

Author: Byron

Cargo.toml

@@ -31,15 +31,18 @@ default = ["max"]
 ## Everything, all at once.
 ##
 ## As fast as possible, with TUI progress, progress line rendering with auto-configuration, all transports based on their most mature implementation (HTTP), all `ein` tools, CLI colors and local-time support, JSON output, regex support for rev-specs.
-max = ["fast", "pretty-cli", "http-client-curl", "gitoxide-core-tools-query", "gitoxide-core-tools", "gitoxide-core-blocking-client", "prodash-render-line", "prodash-render-tui", "prodash/render-line-autoconfigure", "gix/regex" ]
+max = ["max-control", "fast", "gitoxide-core-blocking-client", "http-client-curl"]
 
 ## Like `max`, but only Rust is allowed.
 ##
 ## This is the most compatible build as it won't need a C compiler or C toolchains to build. It's also not the fastest as or the most feature-rich in terms of available
 ## transports as it uses Rust's HTTP implementation.
 ##
 ## As fast as possible, with TUI progress, progress line rendering with auto-configuration, all transports available but less mature pure Rust HTTP implementation, all `ein` tools, CLI colors and local-time support, JSON output, regex support for rev-specs.
-max-pure = ["pretty-cli", "gix-features/rustsha1", "gix-features/zlib-rust-backend", "prodash-render-line", "prodash-render-tui", "gix/max-performance-safe", "gix/comfort", "http-client-reqwest", "gitoxide-core-blocking-client", "gitoxide-core-tools", "prodash/render-line-autoconfigure", "gix/regex" ]
+max-pure = ["max-control", "gix-features/rustsha1", "gix-features/zlib-rust-backend", "http-client-reqwest", "gitoxide-core-blocking-client" ]
+
+## Like `max`, but with more control for configuration. See the *Package Maintainers* headline for more information.
+max-control = ["fast-safe", "pretty-cli", "gitoxide-core-tools-query", "gitoxide-core-tools", "prodash-render-line", "prodash-render-tui", "prodash/render-line-autoconfigure", "gix/regex" ]
 
 ## All of the good stuff, with less fanciness for smaller binaries.
 ##
@@ -64,6 +67,29 @@ small = ["pretty-cli", "gix-features/rustsha1", "gix-features/zlib-rust-backend"
 ## It uses, however, a fully asynchronous networking implementation which can serve a real-world example on how to implement custom async transports.
 lean-async = ["fast", "pretty-cli", "gitoxide-core-tools", "gitoxide-core-tools-query", "gitoxide-core-async-client", "prodash-render-line"]
 
+#! ### Package Maintainers
+#! `*-control` features leave it to you to configure C libraries, involving choices for `zlib`, ! hashing and transport implementation.
+#!
+#! Additional features *can* be provided with `--features` and are handled by the [`gix-features` crate](https://docs.rs/gix-features/latest).
+#! If nothing else is specified, the Rust implementation is used. ! Note that only one feature of each section can be enabled at a time.
+#!
+#! * **zlib**
+#!     - `gix-features/zlib-ng`
+#!     - `gix-features/zlib-ng-compat`
+#!     - `gix-features/zlib-stock`
+#!     - `gix-features/zlib-rust-backend` (*default if no choice is made*)
+#! * **sha1**
+#!     - `gix-features/fast-sha1`
+#!     - `gix-features/rustsha1` (*default if no choice is made*)
+#! * **HTTP** - see the *Building Blocks for mutually exclusive networking* headline
+#!
+#! #### Examples
+#!
+#! * `cargo build --release --no-default-features --features max-control,gix-features/zlib-stock,gitoxide-core-blocking-client,http-client-curl`
+#!     - Create a build just like `max`, but using the stock `zlib` library instead of `zlib-ng`
+#! * `cargo build --release --no-default-features --features max-control,http-client-reqwest,gitoxide-core-blocking-client,gix-features/fast-sha1`
+#!     - Create a build just like `max-pure`, but with faster hashing due to `fast-sha1`.
+
 #! ### Building Blocks
 #! Typical combinations of features of our dependencies, some of which are referred to in the `gitoxide` crate's code for conditional compilation.
 
@@ -72,6 +98,11 @@ lean-async = ["fast", "pretty-cli", "gitoxide-core-tools", "gitoxide-core-tools-
 ## If disabled, the binary will be visibly smaller.
 fast = ["gix/max-performance", "gix/comfort"]
 
+## Makes the crate execute as fast as possible by supporting parallel computation of otherwise long-running functions
+## as well as fast, hardware accelerated hashing, along with a faster zlib backend.
+## If disabled, the binary will be visibly smaller.
+fast-safe = ["gix/max-performance-safe", "gix/comfort"]
+
 ## Use `clap` 3.0 to build the prettiest, best documented and most user-friendly CLI at the expense of binary size.
 ## Provides a terminal user interface for detailed and exhaustive progress.
 ## Provides a line renderer for leaner progress display, without the need for a full-blown TUI.
@@ -98,14 +129,21 @@ gitoxide-core-tools = ["gitoxide-core/organize", "gitoxide-core/estimate-hours"]
 gitoxide-core-tools-query = ["gitoxide-core-tools", "gitoxide-core/query"]
 
 #! ### Building Blocks for mutually exclusive networking
-#! If some of these are set at the same time a compile error is triggered. This also means that `cargo … --all-features` will fail.
-
+#! Blocking and async features are mutually exclusive and cause a compile-time error. This also means that `cargo … --all-features` will fail.
+#! Within each section, features can be combined.
+#!
+#! #### Blocking
+#! The backends are mutually exclusive, e.g. choose either `curl` or `request`.
+#!
 ## Use blocking client networking.
 gitoxide-core-blocking-client = ["gitoxide-core/blocking-client"]
 ## Support synchronous 'http' and 'https' transports (e.g. for clone, fetch and push) using **curl**.
 http-client-curl = ["gix/blocking-http-transport-curl"]
 ## Support synchronous 'http' and 'https' transports (e.g. for clone, fetch and push) using **reqwest**.
 http-client-reqwest = ["gix/blocking-http-transport-reqwest-rust-tls"]
+
+#! #### Async
+#!
 ## Use async client networking.
 gitoxide-core-async-client = ["gitoxide-core/async-client", "futures-lite"]
 

Makefile

@@ -141,6 +141,7 @@ check: ## Build all code in suitable configurations
 					  && cargo check --no-default-features
 	cd gix-odb && cargo check --features serde
 	cd cargo-smart-release && cargo check --all && cargo check --features vendored-openssl
+	cargo check --no-default-features --features max-control
 
 unit-tests: ## run all unit tests
 	cargo test --all