libos: Make File::read_line optionally strip the ending newline

libos/include/os/File.h

@@ -33,7 +33,7 @@ namespace os
         Result<void> write(StringView str);
         Result<void> write(const Buffer& buf);
 
-        Result<String> read_line();
+        Result<String> read_line(bool keep_newline = true);
 
         Result<void> read(Buffer& buf, usize size);
 

libos/src/File.cpp

@@ -108,7 +108,7 @@ namespace os
         return {};
     }
 
-    Result<String> File::read_line()
+    Result<String> File::read_line(bool keep_newline)
     {
         Vector<char> data;
 
@@ -121,7 +121,11 @@ namespace os
 
             TRY(data.try_append((char)current));
 
-            if (current == '\n') break;
+            if (current == '\n')
+            {
+                if (!keep_newline) data.try_pop();
+                break;
+            }
         }
 
         if (!data.size()) return String {};