Slightly change formatting style

For long expressions, one argument or parameter per line is just easier.

src/libcmd/network-proxy.cc

@@ -25,7 +25,10 @@ static StringSet getExcludingNoProxyVariables()
     static const StringSet excludeVariables{"no_proxy", "NO_PROXY"};
     StringSet variables;
     std::set_difference(
-        networkProxyVariables.begin(), networkProxyVariables.end(), excludeVariables.begin(), excludeVariables.end(),
+        networkProxyVariables.begin(),
+        networkProxyVariables.end(),
+        excludeVariables.begin(),
+        excludeVariables.end(),
         std::inserter(variables, variables.begin()));
     return variables;
 }