Add title to commit links in list view

The short commit message may be truncated making the truncated
portion unreadable. The title of the link should be the commit message
so that the commit message is shown when hovering the commit message
anchor.

Closes gitlab-org/gitlab-ce#42673

app/views/projects/tree/_tree_commit_column.html.haml

 %span.str-truncated
-  = link_to_html commit.redacted_full_title_html, project_commit_path(@project, commit.id), class: 'tree-commit-link'
+  = link_to_html commit.redacted_full_title_html, project_commit_path(@project, commit.id), title: commit.redacted_full_title_html, class: 'tree-commit-link'

changelogs/unreleased/jramsay-42673-commit-tooltip.yml

+---
+title: Add commit message to commit tree anchor title
+merge_request: 22585
+author:
+type: fixed