enhance(citation): render citations server-side (#39373)

Replace citation-js with a Go port of ruby-cff, which GitHub uses for
"Cite this repository", rendering APA and BibTeX server-side and
dropping about 770KB of JS. Output matches GitHub on 1568 of 1571
real-world files, the rest are improvements over GitHub.

- `CITATION.cff` wins over `CITATION.bib`, matched case-insensitively
and through symlinks
- `CITATION.bib` is offered as-is, without APA

Signed-off-by: silverwind <me@silverwind.io>

templates/repo/cite/cite_buttons.tmpl

@@ -1,11 +0,0 @@
-<button type="button" class="ui citation button" id="citation-copy-apa" data-text="">
-APA
-</button>
-<button type="button" class="ui citation button" id="citation-copy-bibtex" data-text="">
-BibTeX
-</button>
-<!-- the value will be updated by initCitationFileCopyContent, the code below is used to avoid UI flicking  -->
-<input id="citation-copy-content" value="" size="1" readonly>
-<button type="button" class="ui icon button" id="citation-clipboard-btn" data-tooltip-content="{{ctx.Locale.Tr "copy"}}" data-clipboard-target="#citation-copy-content">
-	{{svg "octicon-copy"}}
-</button>

templates/repo/cite/cite_modal.tmpl

@@ -4,9 +4,20 @@
 	</div>
 	<div class="content">
 		<div class="ui stackable secondary menu">
-			<div class="ui action input" id="citation-panel">
-				{{template "repo/cite/cite_buttons" .}}
-				<a id="goto-citation-btn" class="ui basic jump icon button" href="{{$.RepoLink}}/src/{{$.BranchName}}/CITATION.cff" data-tooltip-content="{{ctx.Locale.Tr "repo.find_file.go_to_file"}}">
+			<div class="ui action input tw-flex tw-w-full" data-global-init="initRepoCitationPanel">
+				{{if .CitationAPA}}
+				<button type="button" class="ui citation button citation-apa" data-text="{{.CitationAPA}}">
+					APA
+				</button>
+				{{end}}
+				<button type="button" class="ui citation button citation-bibtex" data-text="{{.CitationBibTeX}}">
+					BibTeX
+				</button>
+				<input value="" size="1" readonly autofocus>
+				<button type="button" class="ui icon button citation-copy" data-tooltip-content="{{ctx.Locale.Tr "copy"}}">
+					{{svg "octicon-copy"}}
+				</button>
+				<a class="ui basic jump icon button" href="{{$.RepoLink}}/src/{{$.RefTypeNameSubURL}}/{{PathEscapeSegments $.CitationFileName}}" data-tooltip-content="{{ctx.Locale.Tr "repo.find_file.go_to_file"}}">
 					{{svg "octicon-file-moved"}}
 				</a>
 			</div>

templates/repo/home_sidebar_top.tmpl

@@ -58,9 +58,9 @@
 			</a>
 		{{end}}
 
-		{{if .CitiationExist}}
+		{{if .CitationFileName}}
 			{{template "repo/cite/cite_modal" .}}
-			<a class="flex-text-block muted" id="cite-repo-button">
+			<a class="flex-text-block muted show-modal" href="#" data-modal="#cite-repo-modal">
 				{{svg "octicon-cross-reference"}} {{ctx.Locale.Tr "repo.cite_this_repo"}}
 			</a>
 		{{end}}