tool: reintroduce set file comment code for AmigaOS

Amiga specific code which put the URL in the file comment was perhaps
accidentally removed in b889408500 having
originally been added in 5c215bdbdf.
Reworked to fit the code changes and added it back in.

Reported-by: Michael Trebilcock
Originally-added-by: Chris Young

Closes #9258

src/tool_operate.c

@@ -327,6 +327,22 @@ static CURLcode pre_transfer(struct GlobalConfig *global,
   return result;
 }
 
+#ifdef __AMIGA__
+static void AmigaSetComment(struct per_transfer *per,
+                            CURLcode result)
+{
+  struct OutStruct *outs = &per->outs;
+  if(!result && outs->s_isreg && outs->filename) {
+    /* Set the url (up to 80 chars) as comment for the file */
+    if(strlen(per->this_url) > 78)
+      per->this_url[79] = '\0';
+    SetComment(outs->filename, per->this_url);
+  }
+}
+#else
+#define AmigaSetComment(x,y) Curl_nop_stmt
+#endif
+
 /*
  * Call this after a transfer has completed.
  */
@@ -603,6 +619,8 @@ static CURLcode post_per_transfer(struct GlobalConfig *global,
     }
   }
 
+  AmigaSetComment(per, result);
+
   /* File time can only be set _after_ the file has been closed */
   if(!result && config->remote_time && outs->s_isreg && outs->filename) {
     /* Ask libcurl if we got a remote file time */