chore(deps): bump actions/checkout from 5 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/dependabot.yml

@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"

.github/workflows/rust.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v6
     - name: Build
       run: cargo build --verbose
     - name: Run tests

CHANGELOG.md

@@ -1,5 +1,136 @@
 # `cargo-aur` Changelog
 
+## Unreleased
+
+#### Added
+
+- A new `custom` field in `[package.metadata.aur]` which accepts a list of
+  strings that will be added as-is to the `package()` function of the PKGBUILD.
+  This allows the user to add specific extra commands to their build process.
+  See the README for more details.
+
+## 1.7.1 (2024-03-18)
+
+#### Fixed
+
+- The crypt startup error `unexpected free argument aur`.
+
+## 1.7.0 (2024-03-07)
+
+#### Added
+
+- The `--output` flag for customizing the location of the output produced by
+  `cargo aur`. If unused, the default remains `target/cargo-aur/`.
+- A new `files` field in `[package.metadata.aur]`, which accepts a list-of-pairs
+  of additional files you want copied to the user's filesystem upon package
+  installation. Output looks like:
+
+```
+package() {
+    install -Dm755 cargo-aur -t "$pkgdir/usr/bin"
+    install -Dm644 LICENSE "$pkgdir/usr/share/licenses/$pkgname/LICENSE"
+    install -Dm644 "/path/to/original/foo.txt" "$pkgdir/path/to/target/foo.txt"
+}
+```
+
+#### Fixed
+
+- Supply the `url` from backup sources if `homepage` is not specified in the `Cargo.toml`.
+
+## 1.6.0 (2023-10-02)
+
+#### Changed
+
+- The `[package.metadata]` section for adding extra dependency information
+  should now be named `[package.metadata.aur]`. The old syntax will still work,
+  but you will be warned. This fixes a conflict with other `cargo` subcommands.
+- The PKGBUILD and tarball are now output to `target/cargo-aur/` to avoid
+  cluttering the top-level of the repo.
+- Reduced binary size.
+
+#### Fixed
+
+- LICENSE file checking is now done via SPDX identifiers.
+
+## 1.5.0 (2022-04-20)
+
+#### Added
+
+- Support for `[[bin]]` sections in `Cargo.toml`, allowing you to specify custom
+  binary names separate from the package name. [#13]
+- Support for specifying PKGBUILD `depends` and `optdepends` via
+  `[package.metadata]`, as in:
+
+```toml
+[package.metadata]
+depends = ["nachos", "pizza"]
+optdepends = ["sushi", "ramen"]
+```
+
+[#13]: https://github.com/fosskers/cargo-aur/pull/13
+
+## 1.4.1 (2021-09-06)
+
+#### Fixed
+
+- `cargo aur` now respects `CARGO_TARGET_DIR`. [#6]
+
+[#6]: https://github.com/fosskers/cargo-aur/pull/6
+
+## 1.4.0 (2021-06-07)
+
+#### Added
+
+- The `conflicts` field is now added to the `PKGBUILD`.
+- Progress messages in the terminal.
+- `LICENSE` detection and installation. If your Rust crate has a license not
+  found in `/usr/share/licenses/common/` (like `MIT`), then `cargo aur` will
+  copy it into the source tarball and have the PKGBUILD install it. Naturally
+  this means you must actually have a `LICENSE` file in your project, or `cargo aur` will complain.
+
+## 1.3.0 (2021-04-05)
+
+#### Changed
+
+- `cargo aur` no longer outputs `options=("strip")`, since this is set by
+  default in `/etc/makepkg.conf`.
+
+## 1.2.0 (2020-08-24)
+
+#### Added
+
+- A `--version` flag to display the current version of `cargo-aur`.
+
+## 1.1.2 (2020-08-11)
+
+#### Added
+
+- When using `--musl`, the user is warned if they don't have the
+  `x86_64-unknown-linux-musl` target installed.
+
+#### Changed
+
+- Run `strip` on the release binary before `tar`ring it.
+
+## 1.1.1 (2020-08-11)
+
+#### Fixed
+
+- A breaking bug in `1.1.0` which prevented it from working at all.
+
+## 1.1.0 (2020-08-10)
+
+#### Added
+
+- The `--musl` flag to compile the release binary with the MUSL target. In most
+  cases, this will result in a fully statically linked binary.
+
+## 1.0.3 (2020-07-18)
+
+#### Changed
+
+- Better release profile which produces smaller binaries.
+
 ## 1.0.2 (2020-06-22)
 
 #### Changed

Cargo.toml

@@ -1,8 +1,8 @@
 [package]
 name = "cargo-aur"
-version = "1.0.2"
+version = "1.7.1"
 authors = ["Colin Woodbury <colin@fosskers.ca>"]
-edition = "2018"
+edition = "2021"
 description = "Prepare Rust projects to be released on the Arch Linux User Repository."
 homepage = "https://github.com/fosskers/cargo-aur"
 repository = "https://github.com/fosskers/cargo-aur"
@@ -12,9 +12,20 @@ keywords = ["cargo", "subcommand", "archlinux", "aur"]
 categories = ["command-line-utilities"]
 
 [dependencies]
-anyhow = "1.0"
-hmac-sha256 = "0.1"
-itertools = "0.9"
-serde = "1.0"
-serde_derive = "1.0"
-toml = "0.5"
+colored = "2.0"
+gumdrop = "0.8"
+hmac-sha256 = "1.1"
+serde = { version = "1.0", features = ["derive"] }
+toml = "0.8"
+
+[profile.release]
+lto = true
+strip = true
+opt-level = "z"
+codegen-units = 1
+panic = "abort"
+
+[package.metadata.aur]
+# depends = ["blah"]
+# files = [[".github/dependabot.yml", "/usr/local/share/cargo-aur/dependabot.yml"]]
+custom = ["echo hi"]

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2020 - 2021 Colin Woodbury
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -1,26 +1,27 @@
 # cargo-aur
 
-[![Build](https://github.com/fosskers/cargo-aur/workflows/Build/badge.svg)](https://github.com/fosskers/cargo-aur/actions)
-[![](https://img.shields.io/crates/v/cargo-aur.svg)](https://crates.io/crates/cargo-aur)
+[![Build](https://github.com/fosskers/cargo-aur/workflows/Build/badge.svg)][3]
+[![](https://img.shields.io/crates/v/cargo-aur.svg)][4]
+![AUR version][5]
 
 `cargo-aur` is a new subcommand for `cargo` that produces a release tarball and
 PKGBUILD file for a Rust project, so that it can be released on the Arch Linux
 User Repository (AUR).
 
 No extra configuration is necessary. As long as your `Cargo.toml` has [the usual
-fields](https://rust-lang.github.io/api-guidelines/documentation.html#c-metadata),
-a PKGBUILD will be generated with all the necessary sections filled out.
+fields][0], a PKGBUILD will be generated with all the necessary sections filled
+out.
 
 ## Installation
 
 Guess what? `cargo-aur` itself is on the AUR! Install it with an AUR-compatible
-package manager like [`aura`](https://github.com/fosskers/aura):
+package manager like [`aura`][1]:
 
 ```
 sudo aura -A cargo-aur-bin
 ```
 
-... or via `cargo`:
+...or via `cargo`:
 
 ```
 cargo install cargo-aur
@@ -28,13 +29,16 @@ cargo install cargo-aur
 
 ## Usage
 
+### Basics
+
 Navigate to a Rust project, and run:
 
 ```
 cargo aur
 ```
 
-This will produce a `foobar-1.2.3-x86_64.tar.gz` tarball and a PKGBUILD.
+This will produce a `foobar-1.2.3-x86_64.tar.gz` tarball and a PKGBUILD within
+`target/cargo-aur`.
 
 If you wish, you can now run `makepkg` to ensure that your package actually builds.
 
@@ -47,6 +51,12 @@ If you wish, you can now run `makepkg` to ensure that your package actually buil
 ==> Finished making: cargo-aur-bin 1.0.0-1 (Wed 10 Jun 2020 08:23:47 PM PDT)
 ```
 
+You can also run `namcap` to verify your package doesn't have errors.
+
+```sh
+> namcap *.zst
+```
+
 Notice that the built package itself is postfixed with `-bin`, which follows the
 AUR standard.
 
@@ -60,3 +70,82 @@ At this point, it is up to you to:
 
 Some of these steps may be automated in `cargo aur` at a later date if there is
 sufficient demand.
+
+### Custom Binary Names
+
+If you specify a `[[bin]]` section in your `Cargo.toml` and set the `name`
+field, this will be used as the binary name to install within the PKGBUILD.
+
+### `depends` and `optdepends`
+
+If your package requires other Arch packages at runtime, you can specify these
+within your `Cargo.toml` like this:
+
+```toml
+[package.metadata.aur]
+depends = ["nachos", "pizza"]
+optdepends = ["sushi", "ramen"]
+```
+
+And these settings will be copied to your PKGBUILD.
+
+### Including Additional Files
+
+The `files` list can be used to designated initial files to be copied the user's
+filesystem. So this:
+
+```toml
+[package.metadata.aur]
+files = [["path/to/local/foo.txt", "/usr/local/share/your-app/foo.txt"]]
+```
+
+will result in this:
+
+```toml
+package() {
+    install -Dm755 your-app -t "$pkgdir/usr/bin"
+    install -Dm644 LICENSE "$pkgdir/usr/share/licenses/$pkgname/LICENSE"
+    install -Dm644 "path/to/local/foo.txt" "$pkgdir/usr/local/share/your-app/foo.txt"
+}
+```
+
+### Custom commands within `package()`
+
+The `custom` list can be used to add specific commands to the `package()`
+function. This config:
+
+```toml
+[package.metadata.aur]
+custom = ["echo hi"]
+```
+
+yields:
+
+```
+package() {
+    install -Dm755 cargo-aur -t "$pkgdir/usr/bin"
+    install -Dm644 LICENSE "$pkgdir/usr/share/licenses/$pkgname/LICENSE"
+    echo hi
+}
+```
+
+**Note:** Caveat emptor. No attempt is made to verify the injected commands.
+
+### Static Binaries
+
+Run with `--musl` to produce a release binary that is statically linked via
+[MUSL][2].
+
+```
+> cargo aur --musl
+> cd target/x86_64-unknown-linux-musl/release/
+> ldd <your-binary>
+    not a dynamic executable
+```
+
+[0]: https://rust-lang.github.io/api-guidelines/documentation.html#c-metadata 
+[1]: https://github.com/fosskers/aura
+[2]: https://musl.libc.org/
+[3]: https://github.com/fosskers/cargo-aur/actions
+[4]: https://crates.io/crates/cargo-aur
+[5]: https://img.shields.io/aur/version/cargo-aur-bin

src/error.rs

@@ -0,0 +1,52 @@
+//! Errors that can occur in this application.
+
+use std::{fmt::Display, path::PathBuf};
+
+pub(crate) enum Error {
+    IO(std::io::Error),
+    Toml(toml::de::Error),
+    Utf8(std::str::Utf8Error),
+    Utf8OsString,
+    MissingMuslTarget,
+    MissingLicense,
+    TargetNotAbsolute(PathBuf),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Error::IO(e) => write!(f, "{}", e),
+            Error::Toml(e) => write!(f, "{}", e),
+            Error::Utf8(e) => write!(f, "{}", e),
+            Error::Utf8OsString => write!(f, "The `OsString` was not UTF-8!"),
+            Error::MissingMuslTarget => write!(
+                f,
+                "Missing target! Try: rustup target add x86_64-unknown-linux-musl"
+            ),
+            Error::MissingLicense => {
+                write!(f, "Missing LICENSE file. See https://choosealicense.com/")
+            }
+            Error::TargetNotAbsolute(p) => {
+                write!(f, "Target filepath is not absolute: {}", p.display())
+            }
+        }
+    }
+}
+
+impl From<std::str::Utf8Error> for Error {
+    fn from(v: std::str::Utf8Error) -> Self {
+        Self::Utf8(v)
+    }
+}
+
+impl From<toml::de::Error> for Error {
+    fn from(v: toml::de::Error) -> Self {
+        Self::Toml(v)
+    }
+}
+
+impl From<std::io::Error> for Error {
+    fn from(v: std::io::Error) -> Self {
+        Self::IO(v)
+    }
+}

src/lib.rs

@@ -0,0 +1,169 @@
+//! Independently testable types and functions.
+
+use serde::Deserialize;
+use std::ops::Not;
+use std::path::{Path, PathBuf};
+
+/// The git forge in which a project's source code is stored.
+pub enum GitHost {
+    Github,
+    Gitlab,
+}
+
+impl GitHost {
+    pub fn source(&self, package: &Package) -> String {
+        match self {
+            GitHost::Github => format!(
+                "{}/releases/download/v$pkgver/{}-$pkgver-x86_64.tar.gz",
+                package.repository, package.name
+            ),
+            GitHost::Gitlab => format!(
+                "{}/-/archive/v$pkgver/{}-$pkgver-x86_64.tar.gz",
+                package.repository, package.name
+            ),
+        }
+    }
+}
+
+/// The critical fields read from a `Cargo.toml` and rewritten into a PKGBUILD.
+#[derive(Deserialize, Debug)]
+pub struct Package {
+    pub name: String,
+    pub version: String,
+    pub authors: Vec<String>,
+    pub description: String,
+    pub repository: String,
+    pub license: String,
+    pub metadata: Option<Metadata>,
+    pub homepage: Option<String>,
+    pub documentation: Option<String>,
+}
+
+impl Package {
+    /// The name of the tarball that should be produced from this `Package`.
+    pub fn tarball(&self, output: &Path) -> PathBuf {
+        output.join(format!("{}-{}-x86_64.tar.gz", self.name, self.version))
+    }
+
+    pub fn git_host(&self) -> Option<GitHost> {
+        if self.repository.starts_with("https://github") {
+            Some(GitHost::Github)
+        } else if self.repository.starts_with("https://gitlab") {
+            Some(GitHost::Gitlab)
+        } else {
+            None
+        }
+    }
+
+    /// Fetch the package URL from its `homepage`, `documentation` or
+    /// `repository` field.
+    pub fn url(&self) -> &str {
+        self.homepage
+            .as_deref()
+            .or(self.documentation.as_deref())
+            .unwrap_or(&self.repository)
+    }
+}
+
+// {
+//     Package {
+//         name: "aura".to_string(),
+//         version: "1.2.3".to_string(),
+//         authors: vec![],
+//         description: "".to_string(),
+//         homepage: "".to_string(),
+//         repository: "".to_string(),
+//         license: "".to_string(),
+//         metadata: None,
+//     }.tarball(Path::new("foobar"))
+// }
+
+/// The `[package.metadata]` TOML block.
+#[derive(Deserialize, Debug)]
+pub struct Metadata {
+    /// Deprecated.
+    #[serde(default)]
+    pub depends: Vec<String>,
+    /// Deprecated.
+    #[serde(default)]
+    pub optdepends: Vec<String>,
+    /// > [package.metadata.aur]
+    pub aur: Option<AUR>,
+}
+
+impl Metadata {
+    /// The metadata block actually has some contents.
+    pub fn non_empty(&self) -> bool {
+        self.depends.is_empty().not()
+            || self.optdepends.is_empty().not()
+            || self
+                .aur
+                .as_ref()
+                .is_some_and(|aur| aur.depends.is_empty().not() || aur.optdepends.is_empty().not())
+    }
+}
+
+impl std::fmt::Display for Metadata {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        // Reconcile which section to read extra dependency information from.
+        // The format we hope the user is using is:
+        //
+        // > [package.metadata.aur]
+        //
+        // But version 1.5 originally supported:
+        //
+        // > [package.metadata]
+        //
+        // To avoid a sudden breakage for users, we support both definition
+        // locations but favour the newer one.
+        //
+        // We print a warning to the user elsewhere if they're still using the
+        // old way.
+        let (deps, opts) = if let Some(aur) = self.aur.as_ref() {
+            (aur.depends.as_slice(), aur.optdepends.as_slice())
+        } else {
+            (self.depends.as_slice(), self.optdepends.as_slice())
+        };
+
+        match deps {
+            [middle @ .., last] => {
+                write!(f, "depends=(")?;
+                for item in middle {
+                    write!(f, "\"{}\" ", item)?;
+                }
+                if opts.is_empty().not() {
+                    writeln!(f, "\"{}\")", last)?;
+                } else {
+                    write!(f, "\"{}\")", last)?;
+                }
+            }
+            [] => {}
+        }
+
+        match opts {
+            [middle @ .., last] => {
+                write!(f, "optdepends=(")?;
+                for item in middle {
+                    write!(f, "\"{}\" ", item)?;
+                }
+                write!(f, "\"{}\")", last)?;
+            }
+            [] => {}
+        }
+
+        Ok(())
+    }
+}
+
+/// The inner values of a `[package.metadata.aur]` TOML block.
+#[derive(Deserialize, Debug)]
+pub struct AUR {
+    #[serde(default)]
+    depends: Vec<String>,
+    #[serde(default)]
+    optdepends: Vec<String>,
+    #[serde(default)]
+    pub files: Vec<(PathBuf, PathBuf)>,
+    #[serde(default)]
+    pub custom: Vec<String>,
+}

src/main.rs

@@ -1,152 +1,355 @@
+mod error;
+
+use crate::error::Error;
+use cargo_aur::{GitHost, Package};
+use colored::*;
+use gumdrop::{Options, ParsingStyle};
 use hmac_sha256::Hash;
-use itertools::Itertools;
-use serde_derive::Deserialize;
-use std::fs;
-use std::process::{self, Command};
+use serde::Deserialize;
+use std::fs::{DirEntry, File};
+use std::io::{BufWriter, Write};
+use std::ops::Not;
+use std::path::{Path, PathBuf};
+use std::process::{Command, ExitCode};
 
-enum GitHost {
-    Github,
-    Gitlab,
-}
+/// Licenses available from the Arch Linux `licenses` package.
+///
+/// That package contains other licenses, but I've excluded here those unlikely
+/// to be used by Rust crates.
+const LICENSES: &[&str] = &[
+    "AGPL-3.0-only",
+    "AGPL-3.0-or-later",
+    "Apache-2.0",
+    "BSL-1.0", // Boost Software License.
+    "GPL-2.0-only",
+    "GPL-2.0-or-later",
+    "GPL-3.0-only",
+    "GPL-3.0-or-later",
+    "LGPL-2.0-only",
+    "LGPL-2.0-or-later",
+    "LGPL-3.0-only",
+    "LGPL-3.0-or-later",
+    "MPL-2.0",   // Mozilla Public License.
+    "Unlicense", // Not to be confused with "Unlicensed".
+];
 
-impl GitHost {
-    fn source(&self, package: &Package) -> String {
-        match self {
-            GitHost::Github => format!(
-                "{}/releases/download/v$pkgver/{}-$pkgver-x86_64.tar.gz",
-                package.repository, package.name
-            ),
-            GitHost::Gitlab => format!(
-                "{}/-/archive/v$pkgver/{}-$pkgver-x86_64.tar.gz",
-                package.repository, package.name
-            ),
-        }
-    }
+#[derive(Options)]
+struct Args {
+    /// Display this help message.
+    help: bool,
+    /// Display the current version of this software.
+    version: bool,
+    /// Set a custom output directory (default: target/).
+    output: Option<PathBuf>,
+    /// Use the MUSL build target to produce a static binary.
+    musl: bool,
+    /// Don't actually build anything.
+    dryrun: bool,
+    /// Absorbs any extra junk arguments.
+    #[options(free)]
+    free: Vec<String>,
 }
 
 #[derive(Deserialize, Debug)]
 struct Config {
     package: Package,
+    #[serde(default)]
+    bin: Vec<Binary>,
+}
+
+impl Config {
+    /// The name of the compiled binary that should be copied to the tarball.
+    fn binary_name(&self) -> &str {
+        self.bin
+            .first()
+            .map(|bin| bin.name.as_str())
+            .unwrap_or(self.package.name.as_str())
+    }
 }
 
 #[derive(Deserialize, Debug)]
-struct Package {
+struct Binary {
     name: String,
-    version: String,
-    authors: Vec<String>,
-    description: String,
-    homepage: String,
-    repository: String,
-    license: String,
 }
 
-impl Package {
-    /// The name of the tarball that should be produced from this `Package`.
-    fn tarball(&self) -> String {
-        format!("{}-{}-x86_64.tar.gz", self.name, self.version)
+fn main() -> ExitCode {
+    let args = Args::parse_args_or_exit(ParsingStyle::AllOptions);
+
+    if args.version {
+        let version = env!("CARGO_PKG_VERSION");
+        println!("{}", version);
+        ExitCode::SUCCESS
+    } else if let Err(e) = work(args) {
+        eprintln!("{} {}: {}", "::".bold(), "Error".bold().red(), e);
+        ExitCode::FAILURE
+    } else {
+        println!("{} {}", "::".bold(), "Done.".bold().green());
+        ExitCode::SUCCESS
+    }
+}
+
+fn work(args: Args) -> Result<(), Error> {
+    // We can't proceed if the user has specified `--musl` but doesn't have the
+    // target installed.
+    if args.musl {
+        p("Checking for musl toolchain...".bold());
+        musl_check()?
     }
 
-    fn git_host(&self) -> Option<GitHost> {
-        if self.repository.starts_with("https://github") {
-            Some(GitHost::Github)
-        } else if self.repository.starts_with("https://gitlab") {
-            Some(GitHost::Gitlab)
-        } else {
-            None
+    // Where cargo expects to read and write to. By default we want to read the
+    // built binary from `target/release` and we want to write our results to
+    // `target/cargo-aur`, but these are configurable by the user.
+    let cargo_target: PathBuf = match std::env::var_os("CARGO_TARGET_DIR") {
+        Some(p) => PathBuf::from(p),
+        None => PathBuf::from("target"),
+    };
+
+    let output = args.output.unwrap_or(cargo_target.join("cargo-aur"));
+
+    // Ensure the target can actually be written to. Otherwise the `tar`
+    // operation later on will fail.
+    std::fs::create_dir_all(&output)?;
+
+    let config = cargo_config()?;
+
+    // Warn if the user if still using the old metadata definition style.
+    if let Some(metadata) = config.package.metadata.as_ref() {
+        if metadata.depends.is_empty().not() || metadata.optdepends.is_empty().not() {
+            p("Use of [package.metadata] is deprecated. Please specify extra dependencies under [package.metadata.aur].".bold().yellow());
         }
     }
-}
 
-fn main() {
-    if let Err(e) = work() {
-        eprintln!("{}", e);
-        process::exit(1)
+    let license = if must_copy_license(&config.package.license) {
+        p("LICENSE file will be installed manually.".bold().yellow());
+        Some(license_file()?)
+    } else {
+        None
+    };
+
+    if args.dryrun.not() {
+        release_build(args.musl)?;
+        tarball(args.musl, &cargo_target, &output, license.as_ref(), &config)?;
+        let sha256: String = sha256sum(&config.package, &output)?;
+
+        // Write the PKGBUILD.
+        let path = output.join("PKGBUILD");
+        let file = BufWriter::new(File::create(path)?);
+        pkgbuild(file, &config, &sha256, license.as_ref())?;
     }
-}
-
-fn work() -> anyhow::Result<()> {
-    let config = cargo_config()?;
-    release_build()?;
-    tarball(&config.package)?;
-    let sha256 = sha256sum(&config.package)?;
-    let pkgbuild = pkgbuild(&config.package, &sha256);
-    fs::write("PKGBUILD", pkgbuild)?;
 
     Ok(())
 }
 
-fn cargo_config() -> anyhow::Result<Config> {
-    let content = fs::read_to_string("Cargo.toml")?;
-    let proj = toml::from_str(&content)?;
-    Ok(proj) // TODO Would like to do this in one line with the above.
+/// Read the `Cargo.toml` for all the fields of concern to this tool.
+fn cargo_config() -> Result<Config, Error> {
+    // NOTE 2023-11-27 Yes it looks silly to be reading the whole thing into a
+    // string here, but the `toml` library doesn't allow deserialization from
+    // anything else but a string.
+    let content = std::fs::read_to_string("Cargo.toml")?;
+    let proj: Config = toml::from_str(&content)?;
+    Ok(proj)
 }
 
-/// Produce a legal PKGBUILD.
-fn pkgbuild(package: &Package, sha256: &str) -> String {
-    format!(
-        r#"{}
-pkgname={}-bin
-pkgver={}
-pkgrel=1
-pkgdesc="{}"
-url="{}"
-license=("{}")
-arch=("x86_64")
-provides=("{}")
-options=("strip")
-source=("{}")
-sha256sums=("{}")
-
-package() {{
-    install -Dm755 {} -t "$pkgdir/usr/bin/"
-}}
-"#,
-        package
-            .authors
-            .iter()
-            .map(|a| format!("# Maintainer: {}", a))
-            .join("\n"),
-        package.name,
-        package.version,
-        package.description,
-        package.homepage,
-        package.license,
-        package.name,
-        package
-            .git_host()
-            .unwrap_or(GitHost::Github)
-            .source(package),
-        sha256,
-        package.name,
-    )
+/// If a AUR package's license isn't included in `/usr/share/licenses/common/`,
+/// then it must be installed manually by the PKGBUILD. MIT and BSD3 are such
+/// missing licenses, and since many Rust crates use them we must make this
+/// check.
+fn must_copy_license(license: &str) -> bool {
+    LICENSES.contains(&license).not()
 }
 
-/// Run `cargo build --release`.
-fn release_build() -> anyhow::Result<()> {
-    Command::new("cargo")
-        .arg("build")
-        .arg("--release")
-        .status()?;
+/// The path to the `LICENSE` file.
+fn license_file() -> Result<DirEntry, Error> {
+    std::fs::read_dir(".")?
+        .filter_map(|entry| entry.ok())
+        .find(|entry| {
+            entry
+                .file_name()
+                .to_str()
+                .map(|s| s.starts_with("LICENSE"))
+                .unwrap_or(false)
+        })
+        .ok_or(Error::MissingLicense)
+}
+
+/// Write a legal PKGBUILD to some `Write` instance (a `File` in this case).
+fn pkgbuild<T>(
+    mut file: T,
+    config: &Config,
+    sha256: &str,
+    license: Option<&DirEntry>,
+) -> Result<(), Error>
+where
+    T: Write,
+{
+    let package = &config.package;
+    let authors = package
+        .authors
+        .iter()
+        .map(|a| format!("# Maintainer: {}", a))
+        .collect::<Vec<_>>()
+        .join("\n");
+    let source = package
+        .git_host()
+        .unwrap_or(GitHost::Github)
+        .source(&config.package);
+
+    writeln!(file, "{}", authors)?;
+    writeln!(file, "#")?;
+    writeln!(
+        file,
+        "# This PKGBUILD was generated by `cargo aur`: https://crates.io/crates/cargo-aur"
+    )?;
+    writeln!(file)?;
+    writeln!(file, "pkgname={}-bin", package.name)?;
+    writeln!(file, "pkgver={}", package.version)?;
+    writeln!(file, "pkgrel=1")?;
+    writeln!(file, "pkgdesc=\"{}\"", package.description)?;
+    writeln!(file, "url=\"{}\"", package.url())?;
+    writeln!(file, "license=(\"{}\")", package.license)?;
+    writeln!(file, "arch=(\"x86_64\")")?;
+    writeln!(file, "provides=(\"{}\")", package.name)?;
+    writeln!(file, "conflicts=(\"{}\")", package.name)?;
+
+    match package.metadata.as_ref() {
+        Some(metadata) if metadata.non_empty() => {
+            writeln!(file, "{}", metadata)?;
+        }
+        Some(_) | None => {}
+    }
+
+    writeln!(file, "source=(\"{}\")", source)?;
+    writeln!(file, "sha256sums=(\"{}\")", sha256)?;
+    writeln!(file)?;
+    writeln!(file, "package() {{")?;
+    writeln!(
+        file,
+        "    install -Dm755 {} -t \"$pkgdir/usr/bin\"",
+        config.binary_name()
+    )?;
+
+    if let Some(lic) = license {
+        let file_name = lic
+            .file_name()
+            .into_string()
+            .map_err(|_| Error::Utf8OsString)?;
+        writeln!(
+            file,
+            "    install -Dm644 {} \"$pkgdir/usr/share/licenses/$pkgname/{}\"",
+            file_name, file_name
+        )?;
+    }
+
+    if let Some(aur) = package.metadata.as_ref().and_then(|m| m.aur.as_ref()) {
+        for (source, target) in aur.files.iter() {
+            if target.has_root().not() {
+                return Err(Error::TargetNotAbsolute(target.to_path_buf()));
+            } else {
+                writeln!(
+                    file,
+                    "    install -Dm644 \"{}\" \"$pkgdir{}\"",
+                    source.display(),
+                    target.display()
+                )?;
+            }
+        }
+
+        for custom in aur.custom.iter() {
+            writeln!(file, "    {}", custom)?;
+        }
+    }
+
+    writeln!(file, "}}")?;
     Ok(())
 }
 
-fn tarball(package: &Package) -> anyhow::Result<()> {
-    let binary = format!("target/release/{}", package.name);
+/// Run `cargo build --release`, potentially building statically.
+fn release_build(musl: bool) -> Result<(), Error> {
+    let mut args = vec!["build", "--release"];
 
-    fs::copy(binary, &package.name)?;
-    Command::new("tar")
+    if musl {
+        args.push("--target=x86_64-unknown-linux-musl");
+    }
+
+    p("Running release build...".bold());
+    Command::new("cargo").args(args).status()?;
+    Ok(())
+}
+
+fn tarball(
+    musl: bool,
+    cargo_target: &Path,
+    output: &Path,
+    license: Option<&DirEntry>,
+    config: &Config,
+) -> Result<(), Error> {
+    let release_dir = if musl {
+        "x86_64-unknown-linux-musl/release"
+    } else {
+        "release"
+    };
+
+    let binary_name = config.binary_name();
+    let binary = cargo_target.join(release_dir).join(binary_name);
+
+    strip(&binary)?;
+    std::fs::copy(binary, binary_name)?;
+
+    // Create the tarball.
+    p("Packing tarball...".bold());
+    let mut command = Command::new("tar");
+    command
         .arg("czf")
-        .arg(package.tarball())
-        .arg(&package.name)
-        .status()?;
-    fs::remove_file(&package.name)?;
+        .arg(config.package.tarball(output))
+        .arg(binary_name);
+    if let Some(lic) = license {
+        command.arg(lic.path());
+    }
+    if let Some(files) = config
+        .package
+        .metadata
+        .as_ref()
+        .and_then(|m| m.aur.as_ref())
+        .map(|a| a.files.as_slice())
+    {
+        for (file, _) in files {
+            command.arg(file);
+        }
+    }
+    command.status()?;
+
+    std::fs::remove_file(binary_name)?;
 
     Ok(())
 }
 
-fn sha256sum(package: &Package) -> anyhow::Result<String> {
-    let bytes = fs::read(package.tarball())?;
+/// Strip the release binary, so that we aren't compressing more bytes than we
+/// need to.
+fn strip(path: &Path) -> Result<(), Error> {
+    p("Stripping binary...".bold());
+    Command::new("strip").arg(path).status()?;
+    Ok(()) // FIXME Would love to use my `void` package here and elsewhere.
+}
+
+fn sha256sum(package: &Package, output: &Path) -> Result<String, Error> {
+    let bytes = std::fs::read(package.tarball(output))?;
     let digest = Hash::hash(&bytes);
     let hex = digest.iter().map(|u| format!("{:02x}", u)).collect();
     Ok(hex)
 }
+
+/// Does the user have the `x86_64-unknown-linux-musl` target installed?
+fn musl_check() -> Result<(), Error> {
+    let args = ["target", "list", "--installed"];
+    let output = Command::new("rustup").args(args).output()?.stdout;
+
+    std::str::from_utf8(&output)?
+        .lines()
+        .any(|tc| tc == "x86_64-unknown-linux-musl")
+        .then_some(())
+        .ok_or(Error::MissingMuslTarget)
+}
+
+fn p(msg: ColoredString) {
+    println!("{} {}", "::".bold(), msg)
+}