Refactor

This refactors a huge chunk of the code base to make it more maintainable.

Main points:

* Proper separation between bin and lib. Bin handles argument parsing &
  validation and (most of) the output. Lib provides interfaces for all
  opreations.

* Before, libgit2 internals were literred throughout the codebase,
  mainly the `Repository` struct and `git2::Error` in Results. They
  library is now properly wrapped in `repo.rs`, which exposes only the
  required functionality. It also standardizes the Error messages
  (they're just Strings for now) and handles stuff like the copious
  usage of Options to wrap maybe-invalid-utf-8 values. The program will
  still panic on non-utf-8 Strings e.g. in git remotes, but I guess this
  is acceptable. If you actually manage to hit this case, I promise I'll
  fix it :D

* Many unwraps() are now gone and properly handled.

* The table printing functionality is now confined to `table.rs`,
  instead of passing tables as parameters through the whole program.

src/grm/cmd.rs

@@ -0,0 +1,129 @@
+use clap::{AppSettings, Parser};
+
+#[derive(Parser)]
+#[clap(
+    name = clap::crate_name!(),
+    version = clap::crate_version!(),
+    author = clap::crate_authors!("\n"),
+    about = clap::crate_description!(),
+    long_version = clap::crate_version!(),
+    license = clap::crate_license!(),
+    setting = AppSettings::DeriveDisplayOrder,
+    setting = AppSettings::PropagateVersion,
+    setting = AppSettings::HelpRequired,
+)]
+pub struct Opts {
+    #[clap(subcommand)]
+    pub subcmd: SubCommand,
+}
+
+#[derive(Parser)]
+pub enum SubCommand {
+    #[clap(about = "Manage repositories")]
+    Repos(Repos),
+    #[clap(visible_alias = "wt", about = "Manage worktrees")]
+    Worktree(Worktree),
+}
+
+#[derive(Parser)]
+pub struct Repos {
+    #[clap(subcommand, name = "action")]
+    pub action: ReposAction,
+}
+
+#[derive(Parser)]
+pub enum ReposAction {
+    #[clap(
+        visible_alias = "run",
+        about = "Synchronize the repositories to the configured values"
+    )]
+    Sync(Sync),
+    #[clap(about = "Generate a repository configuration from an existing file tree")]
+    Find(Find),
+    #[clap(about = "Show status of configured repositories")]
+    Status(OptionalConfig),
+}
+
+#[derive(Parser)]
+#[clap()]
+pub struct Sync {
+    #[clap(
+        short,
+        long,
+        default_value = "./config.toml",
+        about = "Path to the configuration file"
+    )]
+    pub config: String,
+}
+
+#[derive(Parser)]
+#[clap()]
+pub struct OptionalConfig {
+    #[clap(short, long, about = "Path to the configuration file")]
+    pub config: Option<String>,
+}
+
+#[derive(Parser)]
+pub struct Find {
+    #[clap(about = "The path to search through")]
+    pub path: String,
+}
+
+#[derive(Parser)]
+pub struct Worktree {
+    #[clap(subcommand, name = "action")]
+    pub action: WorktreeAction,
+}
+
+#[derive(Parser)]
+pub enum WorktreeAction {
+    #[clap(about = "Add a new worktree")]
+    Add(WorktreeAddArgs),
+    #[clap(about = "Add an existing worktree")]
+    Delete(WorktreeDeleteArgs),
+    #[clap(about = "Show state of existing worktrees")]
+    Status(WorktreeStatusArgs),
+    #[clap(about = "Convert a normal repository to a worktree setup")]
+    Convert(WorktreeConvertArgs),
+    #[clap(about = "Clean all worktrees that do not contain uncommited/unpushed changes")]
+    Clean(WorktreeCleanArgs),
+}
+
+#[derive(Parser)]
+pub struct WorktreeAddArgs {
+    #[clap(about = "Name of the worktree")]
+    pub name: String,
+
+    #[clap(
+        short = 'n',
+        long = "branch-namespace",
+        about = "Namespace of the branch"
+    )]
+    pub branch_namespace: Option<String>,
+    #[clap(short = 't', long = "track", about = "Remote branch to track")]
+    pub track: Option<String>,
+}
+#[derive(Parser)]
+pub struct WorktreeDeleteArgs {
+    #[clap(about = "Name of the worktree")]
+    pub name: String,
+
+    #[clap(
+        long = "force",
+        about = "Force deletion, even when there are uncommitted/unpushed changes"
+    )]
+    pub force: bool,
+}
+
+#[derive(Parser)]
+pub struct WorktreeStatusArgs {}
+
+#[derive(Parser)]
+pub struct WorktreeConvertArgs {}
+
+#[derive(Parser)]
+pub struct WorktreeCleanArgs {}
+
+pub fn parse() -> Opts {
+    Opts::parse()
+}