Implement list-dead subcommand

This patch implements a helper in imag-ref to list all dead references
either by store id or by path which is referenced.

Suggested-by: Leon Schürmann <leon@is.currently.online>
Signed-off-by: Matthias Beyer <mail@beyermatthias.de>

bin/core/imag-ref/src/main.rs

@@ -77,6 +77,7 @@ fn main() {
                 "deref"     => deref(&rt),
                 "create"    => create(&rt),
                 "remove"    => remove(&rt),
+                "list-dead" => list_dead(&rt),
                 other => {
                     debug!("Unknown command");
                     let _ = rt.handle_unknown_subcommand("imag-ref", other, rt.cli())
@@ -161,6 +162,47 @@ fn remove(rt: &Runtime) {
         });
 }
 
+fn list_dead(rt: &Runtime) {
+    let cfg        = get_ref_config(&rt, "imag-ref").map_err_trace_exit_unwrap();
+    let cmd        = rt.cli().subcommand_matches("list-dead").unwrap(); // safe by main()
+    let list_path  = cmd.is_present("list-dead-pathes");
+    let list_id    = cmd.is_present("list-dead-ids");
+    let mut output = rt.stdout();
+
+    rt.ids::<::ui::PathProvider>()
+        .map_err_trace_exit_unwrap()
+        .into_iter()
+        .for_each(|id| {
+            match rt.store().get(id.clone()).map_err_trace_exit_unwrap() {
+                Some(entry) => {
+                    let entry_path = entry
+                        .as_ref_with_hasher::<DefaultHasher>()
+                        .get_path(&cfg)
+                        .map_err_trace_exit_unwrap();
+
+                    if !entry_path.exists() {
+                        if list_id {
+                            writeln!(output, "{}", entry.get_location().local().display())
+                        } else if list_path {
+                            writeln!(output, "{}", entry_path.display())
+                        } else {
+                            unimplemented!()
+                        }
+                        .map_err(Error::from)
+                        .map_err_trace_exit_unwrap();
+
+                        let _ = rt.report_touched(entry.get_location()).unwrap_or_exit();
+                    }
+                }
+
+                None => {
+                    error!("Does not exist: {}", id.local().display());
+                    exit(1)
+                }
+            }
+        });
+}
+
 fn create(rt: &Runtime) {
     unimplemented!()
 }