give Comment a timestamp, display in chronological order

This commit makes a couple of changes:

- `ent show ISSUE` now displays the Issue's Comments in chronological
  order

- the Comment struct now includes a timestamp, which is the Author Time
  of the oldest commit that touches the comment's directory

- the Issue struct now stores its Comments in a sorted Vec, not in
  a HashMap

- The Comment's uuid moved into the Comment struct itself, instead of
  being the key in the Issue's HashMap of Comments

src/issue.rs

@@ -23,7 +23,7 @@ pub struct Issue {
     pub description: String,
     pub state: State,
     pub dependencies: Option<Vec<IssueHandle>>,
-    pub comments: std::collections::HashMap<String, crate::comment::Comment>,
+    pub comments: Vec<crate::comment::Comment>,
 
     /// This is the directory that the issue lives in.  Only used
     /// internally by the entomologist library.
@@ -85,7 +85,7 @@ impl Issue {
         let mut description: Option<String> = None;
         let mut state = State::New; // default state, if not specified in the issue
         let mut dependencies: Option<Vec<String>> = None;
-        let mut comments = std::collections::HashMap::<String, crate::comment::Comment>::new();
+        let mut comments = Vec::<crate::comment::Comment>::new();
 
         for direntry in dir.read_dir()? {
             if let Ok(direntry) = direntry {
@@ -127,16 +127,16 @@ impl Issue {
     }
 
     fn read_comments(
-        comments: &mut std::collections::HashMap<String, crate::comment::Comment>,
+        comments: &mut Vec<crate::comment::Comment>,
         dir: &std::path::Path,
     ) -> Result<(), IssueError> {
         for direntry in dir.read_dir()? {
             if let Ok(direntry) = direntry {
-                let uuid = direntry.file_name();
                 let comment = crate::comment::Comment::new_from_dir(&direntry.path())?;
-                comments.insert(String::from(uuid.to_string_lossy()), comment);
+                comments.push(comment);
             }
         }
+        comments.sort_by(|a, b| a.timestamp.cmp(&b.timestamp));
         Ok(())
     }
 
@@ -148,10 +148,13 @@ impl Issue {
         }
 
         let rnd: u128 = rand::random();
-        dir.push(&format!("{:032x}", rnd));
+        let uuid = format!("{:032x}", rnd);
+        dir.push(&uuid);
         std::fs::create_dir(&dir)?;
 
         Ok(crate::comment::Comment {
+            uuid,
+            timestamp: chrono::Local::now(),
             description: String::from(""), // FIXME
             dir,
         })
@@ -166,7 +169,7 @@ impl Issue {
             description: String::from(""), // FIXME: kind of bogus to use the empty string as None
             state: State::New,
             dependencies: None,
-            comments: std::collections::HashMap::<String, crate::comment::Comment>::new(),
+            comments: Vec::<crate::comment::Comment>::new(),
             dir: issue_dir,
         })
     }
@@ -242,7 +245,7 @@ mod tests {
             description: String::from("this is the title of my issue\n\nThis is the description of my issue.\nIt is multiple lines.\n* Arbitrary contents\n* But let's use markdown by convention\n"),
             state: State::New,
             dependencies: None,
-            comments: std::collections::HashMap::<String, crate::comment::Comment>::new(),
+            comments: Vec::<crate::comment::Comment>::new(),
             dir: std::path::PathBuf::from(issue_dir),
         };
         assert_eq!(issue, expected);
@@ -256,7 +259,7 @@ mod tests {
             description: String::from("minimal"),
             state: State::InProgress,
             dependencies: None,
-            comments: std::collections::HashMap::<String, crate::comment::Comment>::new(),
+            comments: Vec::<crate::comment::Comment>::new(),
             dir: std::path::PathBuf::from(issue_dir),
         };
         assert_eq!(issue, expected);