refactor: Split out clap_builder for faster derive builds

For now, we are still treating `clap` as the user facing API for both
builder and derive, making this an internal change as we don't expect
this to negatively impact builder build times all that much.  We can
re-evaluate at a later time and consider having distinct top-level
crates for builder and derive.

Looking at `--timings` on my machine
- `clap` only took 0.04s to build and it happened in
  parallel to `clap_builder` codegen
- this saved 1.7s for derive build times, with `clap_builder` building
  in parallel to `syn` and `clap_builder` and `clap_derive` finishing
  around the same time.

This was discussed some at https://rust-lang.zulipchat.com/#narrow/stream/220302-wg-cli/topic/clap.20build.20times.20and.20.60clap_derive.60.3A.20a.20crazy.20idea

Cargo.toml

@@ -1,6 +1,7 @@
 [workspace]
 members = [
   "clap_bench",
+  "clap_builder",
   "clap_derive",
   "clap_lex",
   "clap_complete",
@@ -70,45 +71,37 @@ default = [
   "error-context",
   "suggestions",
 ]
-debug = ["clap_derive?/debug", "dep:backtrace"] # Enables debug messages
-unstable-doc = ["derive", "cargo", "wrap_help", "env", "unicode", "string", "unstable-replace"] # for docs.rs
+debug = ["clap_builder/debug", "clap_derive?/debug"] # Enables debug messages
+unstable-doc = ["clap_builder/unstable-doc", "derive"] # for docs.rs
 
 # Used in default
-std = [] # support for no_std in a backwards-compatible way
-color = ["dep:is-terminal", "dep:termcolor"]
-help = []
-usage = []
-error-context = []
-suggestions = ["dep:strsim", "error-context"]
+std = ["clap_builder/std"] # support for no_std in a backwards-compatible way
+color = ["clap_builder/color"]
+help = ["clap_builder/help"]
+usage = ["clap_builder/usage"]
+error-context = ["clap_builder/error-context"]
+suggestions = ["clap_builder/suggestions"]
 
 # Optional
-deprecated = ["clap_derive?/deprecated"] # Guided experience to prepare for next breaking release (at different stages of development, this may become default)
+deprecated = ["clap_builder/deprecated", "clap_derive?/deprecated"] # Guided experience to prepare for next breaking release (at different stages of development, this may become default)
 derive = ["dep:clap_derive", "dep:once_cell"]
-cargo = ["dep:once_cell"] # Disable if you're not using Cargo, enables Cargo-env-var-dependent macros
-wrap_help = ["help", "dep:terminal_size"]
-env = [] # Use environment variables during arg parsing
-unicode = ["dep:unicode-width", "dep:unicase"]  # Support for unicode characters in arguments and help messages
-string = []  # Allow runtime generated strings
+cargo = ["clap_builder/cargo"] # Disable if you're not using Cargo, enables Cargo-env-var-dependent macros
+wrap_help = ["clap_builder/wrap_help"]
+env = ["clap_builder/env"] # Use environment variables during arg parsing
+unicode = ["clap_builder/unicode"]  # Support for unicode characters in arguments and help messages
+string = ["clap_builder/string"]  # Allow runtime generated strings
 
 # In-work features
-unstable-replace = []
-unstable-grouped = []
-unstable-v5 = ["clap_derive?/unstable-v5", "deprecated"]
+unstable-replace = ["clap_builder/unstable-replace"]
+unstable-grouped = ["clap_builder/unstable-grouped"]
+unstable-v5 = ["clap_builder/unstable-v5", "clap_derive?/unstable-v5", "deprecated"]
 
 [lib]
 bench = false
 
 [dependencies]
+clap_builder = { path = "./clap_builder", version = "=4.1.13" }
 clap_derive = { path = "./clap_derive", version = "=4.1.12", optional = true }
-clap_lex = { path = "./clap_lex", version = "0.3.0" }
-bitflags = "1.2.0"
-unicase = { version = "2.6.0", optional = true }
-strsim = { version = "0.10.0",  optional = true }
-is-terminal = { version = "0.4.1",  optional = true }
-termcolor = { version = "1.1.1", optional = true }
-terminal_size = { version = "0.2.1", optional = true }
-backtrace = { version = "0.3.67", optional = true }
-unicode-width = { version = "0.1.9", optional = true }
 once_cell = { version = "1.12.0", optional = true }
 
 [dev-dependencies]

clap_builder/CONTRIBUTING.md

@@ -0,0 +1,3 @@
+# How to Contribute
+
+See the [clap-wide CONTRIBUTING.md](../CONTRIBUTING.md).  This will contain `clap_builder` specific notes.

clap_builder/Cargo.toml

@@ -0,0 +1,89 @@
+[package]
+name = "clap_builder"
+version = "4.1.13"
+description = "A simple to use, efficient, and full-featured Command Line Argument Parser"
+repository = "https://github.com/clap-rs/clap"
+categories = ["command-line-interface"]
+keywords = [
+  "argument",
+  "cli",
+  "arg",
+  "parser",
+  "parse"
+]
+license.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+include.workspace = true
+
+[package.metadata.docs.rs]
+features = ["unstable-doc"]
+rustdoc-args = ["--cfg", "docsrs"]
+cargo-args = ["-Zunstable-options", "-Zrustdoc-scrape-examples"]
+
+[package.metadata.playground]
+features = ["unstable-doc"]
+
+[package.metadata.release]
+shared-version = true
+dependent-version = "upgrade"
+tag-name = "v{{version}}"
+
+[features]
+default = [
+  "std",
+  "color",
+  "help",
+  "usage",
+  "error-context",
+  "suggestions",
+]
+debug = ["dep:backtrace"] # Enables debug messages
+unstable-doc = ["cargo", "wrap_help", "env", "unicode", "string", "unstable-replace"] # for docs.rs
+
+# Used in default
+std = [] # support for no_std in a backwards-compatible way
+color = ["dep:is-terminal", "dep:termcolor"]
+help = []
+usage = []
+error-context = []
+suggestions = ["dep:strsim", "error-context"]
+
+# Optional
+deprecated = [] # Guided experience to prepare for next breaking release (at different stages of development, this may become default)
+cargo = ["dep:once_cell"] # Disable if you're not using Cargo, enables Cargo-env-var-dependent macros
+wrap_help = ["help", "dep:terminal_size"]
+env = [] # Use environment variables during arg parsing
+unicode = ["dep:unicode-width", "dep:unicase"]  # Support for unicode characters in arguments and help messages
+string = []  # Allow runtime generated strings
+
+# In-work features
+unstable-replace = []
+unstable-grouped = []
+unstable-v5 = ["deprecated"]
+
+[lib]
+bench = false
+
+[dependencies]
+clap_lex = { path = "../clap_lex", version = "0.3.0" }
+bitflags = "1.2.0"
+unicase = { version = "2.6.0", optional = true }
+strsim = { version = "0.10.0",  optional = true }
+is-terminal = { version = "0.4.1",  optional = true }
+termcolor = { version = "1.1.1", optional = true }
+terminal_size = { version = "0.2.1", optional = true }
+backtrace = { version = "0.3.67", optional = true }
+unicode-width = { version = "0.1.9", optional = true }
+once_cell = { version = "1.12.0", optional = true }
+
+[dev-dependencies]
+trybuild = "1.0.77"
+rustversion = "1.0.12"
+# Cutting out `filesystem` feature
+trycmd = { version = "0.14.15", default-features = false, features = ["color-auto", "diff", "examples"] }
+humantime = "2.1.0"
+snapbox = "0.4.10"
+shlex = "1.1.0"
+static_assertions = "1.1.0"
+unic-emoji-char = "0.9.0"