Merge branch '19550-fix-contributer-graph-duplicates' into 'master'

Resolve "contributor emails in contributors graphs is case sensitive"

## What does this MR do?

changes author email to a case insensitive comparison so emails like "Somebody@foo.com" and "somebody@foo.com" are treated as a single author in contribution graphs.

## Are there points in the code the reviewer needs to double check?

should be pretty simple

## Why was this MR needed?

see above description

## Screenshots (if relevant)

#### before:
![before](/uploads/873a073e8d31e1094da6f050ba3e3f51/before.png)

#### after:
![after](/uploads/b9e534755615994f3e58442141c17f86/after.png)


## Does this MR meet the acceptance criteria?

- [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] ~~[Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- [ ] ~~API support added~~
- Tests
  - [ ] ~~Added for this feature/bug~~
  - [ ] ~~All builds are passing~~
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Closes #19550

See merge request !8021

app/assets/javascripts/graphs/stat_graph_contributors_util.js

@@ -2,7 +2,7 @@
 (function() {
   window.ContributorsStatGraphUtil = {
     parse_log: function(log) {
-      var by_author, by_email, data, entry, i, len, total;
+      var by_author, by_email, data, entry, i, len, total, normalized_email;
       total = {};
       by_author = {};
       by_email = {};
@@ -11,7 +11,8 @@
         if (total[entry.date] == null) {
           this.add_date(entry.date, total);
         }
-        data = by_author[entry.author_name] || by_email[entry.author_email];
+        normalized_email = entry.author_email.toLowerCase();
+        data = by_author[entry.author_name] || by_email[normalized_email];
         if (data == null) {
           data = this.add_author(entry, by_author, by_email);
         }
@@ -32,12 +33,14 @@
       return collection[date].date = date;
     },
     add_author: function(author, by_author, by_email) {
-      var data;
+      var data, normalized_email;
       data = {};
       data.author_name = author.author_name;
       data.author_email = author.author_email;
+      normalized_email = author.author_email.toLowerCase();
       by_author[author.author_name] = data;
-      return by_email[author.author_email] = data;
+      by_email[normalized_email] = data;
+      return data;
     },
     store_data: function(entry, total, by_author) {
       this.store_commits(total, by_author);

changelogs/unreleased/19550-fix-contributer-graph-duplicates.yml

+---
+title: group authors in contribution graph with case insensitive email handle comparison
+merge_request: 8021
+author: