Improve unification of contributors by taking the lower-case email as identity

Additionally we sort contributors by name in case they have the same
amount of commits to assure stable results, which may help in some
cases where similar commits counts would be displayed as they
are in the top 3.

Author: Byron

src/info/repo.rs

@@ -23,14 +23,22 @@ pub struct Repo<'a> {
     time_of_first_commit: git::actor::Time,
 }
 
-#[derive(Hash, PartialEq, Eq)]
+#[derive(Hash, PartialEq, Eq, Ord, PartialOrd)]
 pub struct Sig {
     name: git::bstr::BString,
     email: git::bstr::BString,
 }
 
 impl From<git::actor::Signature> for Sig {
-    fn from(git::actor::Signature { name, email, .. }: git::actor::Signature) -> Self {
+    fn from(
+        git::actor::Signature {
+            name, mut email, ..
+        }: git::actor::Signature,
+    ) -> Self {
+        // authors who aren't mail-mapped would otherwise seem dissimilar if the email case is different.
+        // Explicitly lower-casing it normalizes for that.
+        // This comes at the cost of displaying only lower-case emails as well, which seems beneficial.
+        email.make_ascii_lowercase();
         Self { name, email }
     }
 }
@@ -90,7 +98,8 @@ impl<'a> Repo<'a> {
             author_to_number_of_commits.into_iter().collect();
 
         let total_num_authors = authors_by_number_of_commits.len();
-        authors_by_number_of_commits.sort_by(|(_, a_count), (_, b_count)| b_count.cmp(a_count));
+        authors_by_number_of_commits
+            .sort_by(|(sa, a_count), (sb, b_count)| b_count.cmp(a_count).then_with(|| sa.cmp(&sb)));
 
         let authors: Vec<Author> = authors_by_number_of_commits
             .into_iter()