restructure project into a virtual manifest

- remove redundant readme
- de-duplicate Cargo.toml information using workspace inheritance
- rename "pacdef_core" to "pacdef"
- move "crates/main/main.rs" to "crates/pacdef/src/main.rs"

crates/pacdef/src/backend/actual/arch.rs

@@ -0,0 +1,129 @@
+use std::collections::HashSet;
+use std::process::Command;
+
+use alpm::Alpm;
+use alpm::PackageReason::Explicit;
+use anyhow::{Context, Result};
+
+use crate::backend::backend_trait::{Backend, Switches, Text};
+use crate::backend::macros::impl_backend_constants;
+use crate::cmd::run_external_command;
+use crate::{Group, Package};
+
+#[derive(Debug, Clone)]
+pub struct Arch {
+    pub(crate) binary: String,
+    pub(crate) aur_rm_args: Vec<String>,
+    pub(crate) packages: HashSet<Package>,
+}
+
+const BINARY: Text = "pacman";
+const SECTION: Text = "arch";
+
+const SWITCHES_INFO: Switches = &["--query", "--info"];
+const SWITCHES_INSTALL: Switches = &["--sync"];
+const SWITCHES_MAKE_DEPENDENCY: Switches = &["--database", "--asdeps"];
+const SWITCHES_NOCONFIRM: Switches = &["--noconfirm"];
+const SWITCHES_REMOVE: Switches = &["--remove", "--recursive"];
+
+const SUPPORTS_AS_DEPENDENCY: bool = true;
+
+impl Backend for Arch {
+    impl_backend_constants!();
+
+    fn get_binary(&self) -> Text {
+        let r#box = self.binary.clone().into_boxed_str();
+        Box::leak(r#box)
+    }
+
+    fn get_all_installed_packages(&self) -> Result<HashSet<Package>> {
+        let alpm_packages = get_all_installed_packages_from_alpm()
+            .context("getting all installed packages from alpm")?;
+
+        let result = convert_to_pacdef_packages(alpm_packages);
+        Ok(result)
+    }
+
+    fn get_explicitly_installed_packages(&self) -> Result<HashSet<Package>> {
+        let alpm_packages = get_explicitly_installed_packages_from_alpm()
+            .context("getting all installed packages from alpm")?;
+        let result = convert_to_pacdef_packages(alpm_packages);
+        Ok(result)
+    }
+
+    /// Install the specified packages.
+    fn install_packages(&self, packages: &[Package], noconfirm: bool) -> Result<()> {
+        let mut cmd = Command::new(&self.binary);
+
+        cmd.args(self.get_switches_install());
+
+        if noconfirm {
+            cmd.args(self.get_switches_noconfirm());
+        }
+
+        for p in packages {
+            cmd.arg(format!("{p}"));
+        }
+
+        run_external_command(cmd)
+    }
+
+    /// Remove the specified packages.
+    fn remove_packages(&self, packages: &[Package], noconfirm: bool) -> Result<()> {
+        let mut cmd = Command::new(&self.binary);
+
+        cmd.args(self.get_switches_remove());
+        cmd.args(&self.aur_rm_args);
+
+        if noconfirm {
+            cmd.args(self.get_switches_noconfirm());
+        }
+
+        for p in packages {
+            cmd.arg(format!("{p}"));
+        }
+
+        run_external_command(cmd)
+    }
+}
+
+fn get_all_installed_packages_from_alpm() -> Result<HashSet<String>> {
+    let db = get_db_handle().context("getting DB handle")?;
+    let result = db
+        .localdb()
+        .pkgs()
+        .iter()
+        .map(|p| p.name().to_string())
+        .collect();
+    Ok(result)
+}
+
+fn get_explicitly_installed_packages_from_alpm() -> Result<HashSet<String>> {
+    let db = get_db_handle().context("getting DB handle")?;
+    let result = db
+        .localdb()
+        .pkgs()
+        .iter()
+        .filter(|p| p.reason() == Explicit)
+        .map(|p| p.name().to_string())
+        .collect();
+    Ok(result)
+}
+
+fn convert_to_pacdef_packages(packages: HashSet<String>) -> HashSet<Package> {
+    packages.into_iter().map(Package::from).collect()
+}
+
+fn get_db_handle() -> Result<Alpm> {
+    Alpm::new("/", "/var/lib/pacman").context("connecting to DB using expected default values")
+}
+
+impl Arch {
+    pub(crate) fn new() -> Self {
+        Self {
+            binary: BINARY.to_string(),
+            aur_rm_args: vec![],
+            packages: HashSet::new(),
+        }
+    }
+}