[Support][CommandLine] Display subcommands in help when there are less than 3 subcommands

[arphaman]

Summary

This patch fixes a bug where the help output doesn't display subcommands when a tool has less than 3 subcommands.

Unfortunately I couldn't find a way to write a unittest for this change. Please let me know what's the best way to test this change (if any).

llvm/trunk/lib/Support/CommandLine.cpp

for (auto Opt : PositionalOpts) {
         outs() << " --" << Opt->ArgStr;
       outs() << " " << Opt->HelpStr;
     }
 
     // Print the consume after option info if it exists...
     if (ConsumeAfterOpt)
       outs() << " " << ConsumeAfterOpt->HelpStr;
 
-    if (Sub == &*TopLevelSubCommand && Subs.size() > 2) {
+    if (Sub == &*TopLevelSubCommand && !Subs.empty()) {
       // Compute the maximum subcommand length...
       size_t MaxSubLen = 0;
       for (size_t i = 0, e = Subs.size(); i != e; ++i)
         MaxSubLen = std::max(MaxSubLen, strlen(Subs[i].first));
 
       outs() << "\n\n";
       outs() << "SUBCOMMANDS:\n\n";
       printSubCommands(Subs, MaxSubLen);