Logo: trait - as an alias for /dev/stdin

which can be useful where `/dev/stdin` is not available, eg. on Windows

src/fastfetch.c

@@ -1205,7 +1205,8 @@ static void parseArguments(FFdata* data, int argc, const char** argv)
         }
 
         if(i == argc - 1 || (
-            *argv[i + 1] == '-' &&
+            argv[i + 1][0] == '-' &&
+            argv[i + 1][1] != '\0' && // `-` is used as an alias for `/dev/stdin`
             strcasecmp(argv[i], "--separator-string") != 0 // Separator string can start with a -
         )) {
             parseOption(data, argv[i], NULL);

src/logo/logo.c

@@ -359,7 +359,10 @@ static bool logoPrintFileIfExists(bool doColorReplacement, bool raw)
 
     FF_STRBUF_AUTO_DESTROY content = ffStrbufCreate();
 
-    if(!ffAppendFileBuffer(options->source.chars, &content))
+    if(ffStrbufEqualS(&options->source, "-")
+        ? !ffAppendFDBuffer(FFUnixFD2NativeFD(STDIN_FILENO), &content)
+        : !ffAppendFileBuffer(options->source.chars, &content)
+    )
     {
         fprintf(stderr, "Logo: Failed to load file content from logo source: %s \n", options->source.chars);
         return false;