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/main.rs

@@ -0,0 +1,99 @@
+/*!
+Main program for `pacdef`.
+*/
+
+#![warn(
+    clippy::as_conversions,
+    clippy::option_if_let_else,
+    clippy::redundant_pub_crate,
+    clippy::semicolon_if_nothing_returned,
+    clippy::unnecessary_wraps,
+    clippy::unused_self,
+    clippy::unwrap_used,
+    clippy::use_debug,
+    clippy::use_self,
+    clippy::wildcard_dependencies,
+    missing_docs
+)]
+
+use std::path::Path;
+use std::process::{ExitCode, Termination};
+
+use anyhow::{bail, Context, Result};
+
+use pacdef::path::{get_config_path, get_config_path_old_version, get_group_dir};
+use pacdef::{get_args, Config, Error as PacdefError, Group, Pacdef};
+
+const MAJOR_UPDATE_MESSAGE: &str = "VERSION UPGRADE
+You seem to have used version 0.x of pacdef before.
+Version 1.x changes the syntax of the config files and the command line arguments.
+Check out https://github.com/steven-omaha/pacdef for new syntax information.
+This message will not appear again.
+------";
+
+fn main() -> ExitCode {
+    handle_final_result(main_inner())
+}
+
+/// Skip printing the error chain when searching packages yields no results,
+/// otherwise report error chain.
+#[allow(clippy::option_if_let_else)]
+fn handle_final_result(result: Result<()>) -> ExitCode {
+    match result {
+        Ok(_) => ExitCode::SUCCESS,
+        Err(ref e) => {
+            if let Some(root_error) = e.root_cause().downcast_ref::<PacdefError>() {
+                eprintln!("{root_error}");
+                ExitCode::FAILURE
+            } else {
+                result.report()
+            }
+        }
+    }
+}
+
+fn main_inner() -> Result<()> {
+    let args = get_args();
+
+    let config_file = get_config_path().context("getting config file")?;
+
+    let config = match Config::load(&config_file).context("loading config file") {
+        Ok(config) => config,
+        Err(e) => {
+            if let Some(crate_error) = e.downcast_ref::<PacdefError>() {
+                match crate_error {
+                    PacdefError::ConfigFileNotFound => load_default_config(&config_file)?,
+                    _ => bail!("unexpected error: {crate_error}"),
+                }
+            } else {
+                bail!("unexpected error: {e:?}");
+            }
+        }
+    };
+
+    let group_dir = get_group_dir().context("resolving group dir")?;
+    let groups = Group::load(&group_dir, config.warn_not_symlinks)
+        .with_context(|| format!("loading groups under {}", group_dir.to_string_lossy()))?;
+
+    let pacdef = Pacdef::new(args, config, groups);
+    pacdef.run_action_from_arg().context("running action")
+}
+
+fn load_default_config(config_file: &Path) -> Result<Config> {
+    if get_config_path_old_version()?.exists() {
+        println!("{MAJOR_UPDATE_MESSAGE}");
+    }
+
+    if !config_file.exists() {
+        create_empty_config_file(config_file)?;
+    }
+
+    Ok(Config::default())
+}
+
+fn create_empty_config_file(config_file: &Path) -> Result<()> {
+    let config_dir = &config_file.parent().context("getting parent dir")?;
+    std::fs::create_dir_all(config_dir).context("creating parent dir")?;
+    std::fs::File::create(config_file).context("creating empty config file")?;
+    Ok(())
+}