Fix commit's time (#18375)

* Fix commit's time

- Use the Committer's `when` as the CommitDate will be modified when the
commit is being moved around in the git tree(e.g. being rebased on top
of newer commits). The Author's `when` is created once and never touched
again.

* Update templates/repo/view_list.tmpl

* Commmt unstaged

* Add fallback

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

templates/repo/commits_list.tmpl

@@ -75,7 +75,11 @@
 							<pre class="commit-body" style="display: none;">{{RenderCommitBody $.Context .Message $commitRepoLink $.Repository.ComposeMetas}}</pre>
 							{{end}}
 						</td>
-						<td class="text right aligned">{{TimeSince .Author.When $.Lang}}</td>
+						{{if .Committer}}
+							<td class="text right aligned">{{TimeSince .Committer.When $.Lang}}</td>
+						{{else}}
+							<td class="text right aligned">{{TimeSince .Author.When $.Lang}}</td>
+						{{end}}
 					</tr>
 				{{end}}
 			</tbody>