[CommandLine][NFCI] Do not add 'All' to 'RegisteredSubCommands'

After #75679, it is no longer necessary to add the `All` pseudo
subcommand to the list of registered subcommands. The change causes the
list to contain only real subcommands, i.e. an unnamed top-level
subcommand and named ones. This simplifies the code a bit by removing
some checks for this special case.

Author: igorkudrin

llvm/lib/Support/CommandLine.cpp

@@ -164,10 +164,7 @@ class CommandLineParser {
   // This collects the different subcommands that have been registered.
   SmallPtrSet<SubCommand *, 4> RegisteredSubCommands;
 
-  CommandLineParser() {
-    registerSubCommand(&SubCommand::getTopLevel());
-    registerSubCommand(&SubCommand::getAll());
-  }
+  CommandLineParser() { registerSubCommand(&SubCommand::getTopLevel()); }
 
   void ResetAllOptionOccurrences();
 
@@ -348,15 +345,14 @@ class CommandLineParser {
 
     // For all options that have been registered for all subcommands, add the
     // option to this subcommand now.
-    if (sub != &SubCommand::getAll()) {
-      for (auto &E : SubCommand::getAll().OptionsMap) {
-        Option *O = E.second;
-        if ((O->isPositional() || O->isSink() || O->isConsumeAfter()) ||
-            O->hasArgStr())
-          addOption(O, sub);
-        else
-          addLiteralOption(*O, sub, E.first());
-      }
+    assert(sub != &SubCommand::getAll());
+    for (auto &E : SubCommand::getAll().OptionsMap) {
+      Option *O = E.second;
+      if ((O->isPositional() || O->isSink() || O->isConsumeAfter()) ||
+          O->hasArgStr())
+        addOption(O, sub);
+      else
+        addLiteralOption(*O, sub, E.first());
     }
   }
 
@@ -384,7 +380,6 @@ class CommandLineParser {
     SubCommand::getTopLevel().reset();
     SubCommand::getAll().reset();
     registerSubCommand(&SubCommand::getTopLevel());
-    registerSubCommand(&SubCommand::getAll());
 
     DefaultOptions.clear();
   }
@@ -532,8 +527,7 @@ SubCommand *CommandLineParser::LookupSubCommand(StringRef Name,
   // Find a subcommand with the edit distance == 1.
   SubCommand *NearestMatch = nullptr;
   for (auto *S : RegisteredSubCommands) {
-    if (S == &SubCommand::getAll())
-      continue;
+    assert(S != &SubCommand::getAll());
     if (S->getName().empty())
       continue;