Start using template context function (#26254)

Before:

* `{{.locale.Tr ...}}`
* `{{$.locale.Tr ...}}`
* `{{$.root.locale.Tr ...}}`
* `{{template "sub" .}}`
* `{{template "sub" (dict "locale" $.locale)}}`
* `{{template "sub" (dict "root" $)}}`
* .....

With context function: only need to `{{ctx.Locale.Tr ...}}`

The "ctx" could be considered as a super-global variable for all
templates including sub-templates.


To avoid potential risks (any bug in the template context function
package), this PR only starts using "ctx" in "head.tmpl" and
"footer.tmpl" and it has a "DataRaceCheck". If there is anything wrong,
the code can be fixed or reverted easily.

routers/common/errpage.go

@@ -48,7 +48,7 @@ func RenderPanicErrorPage(w http.ResponseWriter, req *http.Request, err any) {
 		data["ErrorMsg"] = "PANIC: " + combinedErr
 	}
 
-	err = templates.HTMLRenderer().HTML(w, http.StatusInternalServerError, string(tplStatus500), data)
+	err = templates.HTMLRenderer().HTML(w, http.StatusInternalServerError, string(tplStatus500), data, nil)
 	if err != nil {
 		log.Error("Error occurs again when rendering error page: %v", err)
 		w.WriteHeader(http.StatusInternalServerError)

routers/install/install.go

@@ -68,9 +68,13 @@ func Contexter() func(next http.Handler) http.Handler {
 			}
 			defer baseCleanUp()
 
+			ctx.TemplateContext = context.NewTemplateContext(ctx)
+			ctx.TemplateContext["Locale"] = ctx.Locale
+
 			ctx.AppendContextValue(context.WebContextKey, ctx)
 			ctx.Data.MergeFrom(middleware.CommonTemplateContextData())
 			ctx.Data.MergeFrom(middleware.ContextData{
+				"Context":        ctx, // TODO: use "ctx" in template and remove this
 				"locale":         ctx.Locale,
 				"Title":          ctx.Locale.Tr("install.install"),
 				"PageIsInstall":  true,

routers/web/auth/oauth.go

@@ -578,7 +578,7 @@ func GrantApplicationOAuth(ctx *context.Context) {
 
 // OIDCWellKnown generates JSON so OIDC clients know Gitea's capabilities
 func OIDCWellKnown(ctx *context.Context) {
-	t, err := ctx.Render.TemplateLookup("user/auth/oidc_wellknown")
+	t, err := ctx.Render.TemplateLookup("user/auth/oidc_wellknown", nil)
 	if err != nil {
 		ctx.ServerError("unable to find template", err)
 		return

routers/web/swagger_json.go

@@ -13,7 +13,7 @@ const tplSwaggerV1Json base.TplName = "swagger/v1_json"
 
 // SwaggerV1Json render swagger v1 json
 func SwaggerV1Json(ctx *context.Context) {
-	t, err := ctx.Render.TemplateLookup(string(tplSwaggerV1Json))
+	t, err := ctx.Render.TemplateLookup(string(tplSwaggerV1Json), nil)
 	if err != nil {
 		ctx.ServerError("unable to find template", err)
 		return