Add basic command line boilerplate and arg parsing

.gitignore

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+/target

Cargo.lock

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+# It is not intended for manual editing.
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+ "serde",
+ "yaml-rust",
+]
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+ "serde_yaml",
+ "toml",
+]
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Cargo.toml

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+[package]
+name = "shepherd"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+serde = { version = "1.0", features = ["derive"] }
+serde_yaml = "0.8"
+toml = "0.5"

src/config.rs

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+use std::error::Error;
+use serde::{Deserialize, Serialize};
+use std::env;
+use std::fs;
+use std::path::Path;
+
+#[derive(Debug, PartialEq, Serialize, Deserialize)]
+/// The internal representation of the configuration file.
+pub struct Config {
+    pub source_dir: String,
+}
+
+impl Config {
+    /// Create new Config struct with default values
+    ///
+    /// The `source_dir` field defaults to `$HOME/sources`
+    pub fn new() -> Config {
+        Config {
+            source_dir: format!("{}/sources", env::var("HOME").unwrap()),
+        }
+    }
+
+    /// Read TOML file and load values into a Config struct
+    ///
+    /// If the filename doesn't exist, read_config() will write the current struct to the given
+    /// config file.
+    pub fn read_config(&mut self, filename: &str) -> Result<(), Box<dyn Error>> {
+        // Load raw yaml file. If the file doesn't exist, create it
+        if std::path::Path::new(filename).exists() {
+            let raw = fs::read_to_string(filename)?;
+            // Convert string to our Config struct
+            let toml: Config = toml::from_str(&raw)?;
+            *self = toml;
+        } else {
+            let config: String = toml::to_string(&self)?;
+            // Get the path to the config file
+            let path = match Path::new(filename).parent()  {
+                Some(x) => x,
+                _ => Path::new(filename)
+            };
+            // Make sure the path exists
+            fs::create_dir_all(path).unwrap();
+            // Write default Config struct to file
+            fs::write(filename, config).expect("Couldn't write file");
+        }
+        Ok(())
+    }
+
+    /// Create a string of the current loaded config.
+    ///
+    /// Useful for dumping the config
+    pub fn to_string(&self) -> Result<String, toml::ser::Error> {
+        toml::to_string_pretty(self)
+    }
+}

src/lib.rs

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+pub mod config;
+use config::Config;
+use std::error::Error;
+use std::env;
+
+#[derive(Debug)]
+/// Holds the current state of the application.
+///
+/// This is used when processing command line arguments, and is thus loaded before the
+/// configuration file is.
+pub struct State {
+    cmd: Option<Cmd>,
+    url: Option<String>,
+    pub config: String,
+}
+
+#[derive(Debug)]
+/// Used to signal which main command is going to be run
+enum Cmd {
+    Fetch,
+    Help,
+    DumpConfig,
+}
+
+impl State {
+    /// Parses command line flags/arguments and creates the application state.
+    ///
+    /// Argument parsing goes left to right. The first not flag argument it comes across is set as
+    /// the cmd.
+    ///
+    /// Parsing priority is as follows:
+    /// - `--long-flag` type arguments
+    /// - `-mcsf` multi character short flag type arguments
+    /// - `command` type arguments
+    pub fn new(mut args: std::env::Args) -> State {
+        let mut state = State {
+            cmd: None,
+            url: None,
+            config: format!("{}/.config/shepherd/config.toml", env::var("HOME").unwrap()),
+        };
+
+        let mut arg = args.next();
+        // Iterate through the command line arguments
+        while let Some(x) = &arg {
+            // Long arguments
+            if x.starts_with("--") {
+                let option = x.strip_prefix("--").unwrap();
+                match option {
+                    "help" => state.cmd = Some(Cmd::Help),
+                    "dump-config" => state.cmd = Some(Cmd::DumpConfig),
+                    "config" => {
+                        let file = args.next();
+                        match file {
+                            Some(x) => state.config = x,
+                            None => eprintln!("Expected config argument"),
+                        }
+                    }
+                    _ => {}
+                }
+            }
+            // short arguments
+            else if x.starts_with("-") {
+                let options = x.strip_prefix("-").unwrap().chars();
+                for opt in options {
+                    match opt {
+                        'h' => state.cmd = Some(Cmd::Help),
+                        _ => {}
+                    }
+                }
+            }
+            // Fetch command
+            else if x == "fetch" {
+                let url = args.next();
+                match url {
+                    Some(x) => match state.cmd {
+                        None => {
+                            state.cmd = Some(Cmd::Fetch);
+                            state.url = Some(x);
+                        }
+                        _ => {}
+                    },
+                    None => {
+                        eprintln!("No URL provided for \'number\' command\n");
+                    }
+                }
+            }
+            arg = args.next();
+        }
+
+        // Fall back to Help command if no other command was given
+        state.cmd = match state.cmd {
+            Some(x) => Some(x),
+            None => Some(Cmd::Help),
+        };
+        state
+    }
+}
+
+pub fn run(state: State, config: Config) -> Result<(), Box<dyn Error>> {
+    match state.cmd {
+        Some(Cmd::Help) => {
+            println!("{}", help_msg());
+        }
+        Some(Cmd::DumpConfig) => {
+            println!("{}", config.to_string().unwrap());
+        }
+        Some(x) => {
+            println!("{:?} hasn't been implemented yet!", x)
+        }
+        _ => {}
+    }
+    Ok(())
+}
+
+fn help_msg() -> String {
+    format!(
+        "Git repository manager
+
+USAGE:
+    shepherd [--help] <command> [<args>]
+
+OPTIONS:
+    -h, --help      Print out this help message
+    --dump-config   dump the current configuration
+
+COMMANDS:
+General
+    help    Print out this help message
+
+Manage Repositories
+    clone   Add another git repo to keep track of
+    fetch   Update currently tracked repos"
+    )
+}

src/main.rs

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+use std::env;
+use shepherd::State;
+use shepherd::config::Config;
+
+fn main() {
+    let args = env::args();
+    let state = State::new(args);
+    let mut config = Config::new();
+    config.read_config(&state.config).unwrap();
+    if let Err(e) = shepherd::run(state, config) {
+        eprintln!("{}", e);
+    }
+}