Implement done command

src/cli/done.rs

@@ -0,0 +1,16 @@
+use chrono::NaiveDateTime;
+
+use crate::eval::Entry;
+use crate::files::commands::Done;
+use crate::files::Files;
+
+use super::error::Result;
+
+pub fn mark_done(files: &mut Files, entry: &Entry, now: NaiveDateTime) -> Result<()> {
+    let done = Done {
+        date: entry.dates.map(|dates| dates.into()),
+        done_at: now.date(),
+    };
+    files.add_done(entry.source, done)?;
+    Ok(())
+}