add tag_is_hashtag to remove some duplicate logic

Signed-off-by: William Casarin <jb55@jb55.com>

damus/Models/SearchModel.swift

@@ -65,10 +65,8 @@ class SearchModel: ObservableObject {
 
 func event_matches_hashtag(_ ev: NostrEvent, hashtags: [String]) -> Bool {
     for tag in ev.tags {
-        if tag.count >= 2 && tag[0] == "hashtag" {
-            if hashtags.contains(tag[1]) {
-                return true
-            }
+        if tag_is_hashtag(tag) && hashtags.contains(tag[1]) {
+            return true
         }
     }
     return false

damus/Nostr/NostrLink.swift

@@ -93,7 +93,7 @@ func decode_nostr_uri(_ s: String) -> NostrLink? {
             return
         }
     
-    if parts.count >= 2 && parts[0] == "hashtag" {
+    if tag_is_hashtag(parts) {
         return .filter(NostrFilter.filter_hashtag([parts[1].lowercased()]))
     }
     

damus/Views/ThreadView.swift

@@ -79,9 +79,13 @@ func should_show_chatroom(_ ev: NostrEvent) -> Bool {
     return has_hashtag(ev.tags, hashtag: "chat")
 }
 
+func tag_is_hashtag(_ tag: [String]) -> Bool {
+    return tag.count >= 2 && (tag[0] == "hashtag" || tag[0] == "t")
+}
+
 func has_hashtag(_ tags: [[String]], hashtag: String) -> Bool {
     for tag in tags {
-        if tag.count >= 2 && (tag[0] == "hashtag" || tag[0] == "t") && tag[1] == hashtag {
+        if tag_is_hashtag(tag) && tag[1] == hashtag {
             return true
         }
     }