Refactor tmpl and blob_excerpt (#32967)

1. do not use `{{/* */}}` to remove spaces, use `{{- -}}`
2. fix "blob_excerpt" endpoint, remove the legacy fragile code: have
tested commit diff and wiki diff

templates/repo/issue/filter_item_label.tmpl

@@ -1,4 +1,4 @@
-{{/*
+{{/* Template Attributes:
 * "labels" from query string (needed by JS)
 * QueryLink
 * Labels

templates/repo/issue/sidebar/milestone_list.tmpl

@@ -6,7 +6,7 @@
 		{{if $pageMeta.Issue}}data-update-url="{{$pageMeta.RepoLink}}/issues/milestone?issue_ids={{$pageMeta.Issue.ID}}"{{end}}
 >
 	<input class="combo-value" name="milestone_id" type="hidden" value="{{$data.SelectedMilestoneID}}">
-	<div class="ui dropdown {{if not $pageMeta.CanModifyIssueOrPull}}disabled{{end}} ">
+	<div class="ui dropdown {{if not $pageMeta.CanModifyIssueOrPull}}disabled{{end}}">
 		<a class="text muted">
 			<strong>{{ctx.Locale.Tr "repo.issues.new.milestone"}}</strong> {{if $pageMeta.CanModifyIssueOrPull}}{{svg "octicon-gear"}}{{end}}
 		</a>

templates/repo/issue/view_content/pull.tmpl

@@ -367,8 +367,7 @@
 				{{end}}
 			{{end}}{{/* end if: pull request status */}}
 
-			{{/*
-			Manually Merged is not a well-known feature, it is used to mark a non-mergeable PR (already merged, conflicted) as merged
+			{{/* Manually Merged is not a well-known feature, it is used to mark a non-mergeable PR (already merged, conflicted) as merged
 			To test it:
 			* Enable "Manually Merged" feature in the Repository Settings
 			* Create a pull request, either: