[lldb] fix --source-quietly

Jim says:

lldb has a -Q or --source-quietly option, which supposedly does:

    --source-quietly     Tells the debugger to execute this one-line lldb command before any file has been loaded.

That seems like a weird description, since we don't generally use source for one line entries, but anyway, let's try it:

    > $LLDB_LLVM/clean-mono/build/Debug/bin/lldb -Q "script print('I should be quiet')" a.out -O "script print('I should be before')" -o "script print('I should be after')"
    (lldb) script print('I should be before')
    I should be before
    (lldb) target create "script print('I should be quiet')"
    error: unable to find executable for 'script print('I should be quiet')'

That was weird.  The first real -O gets sourced but not quietly, then the argument to the -Q gets treated as the target.

    > $LLDB_LLVM/clean-mono/build/Debug/bin/lldb -Q a.out -O "script print('I should be before')" -o "script print('I should be after')"
    (lldb) script print('I should be before')
    I should be before
    (lldb) target create "a.out"
    Current executable set to '/tmp/a.out' (x86_64).
    (lldb) script print('I should be after')
    I should be after

Well, that's a little better, but the -Q option seems to have done nothing.

---

This fixes the description of --source-quietly, as well as causing it
to actually suppress echoing while executing the initialization
commands.

Reviewed By: jingham

Differential Revision: https://reviews.llvm.org/D112988

Author: lawrence-danna-apple

lldb/docs/man/lldb.rst

@@ -111,7 +111,7 @@ COMMANDS
 
 .. option:: --source-quietly
 
- Tells the debugger to execute this one-line lldb command before any file has been loaded.
+ Tells the debugger not to echo commands while sourcing files or one-line commands provided on the command line.
 
 .. option:: --source <file>
 

lldb/test/Shell/Driver/TestQuiet.test

@@ -0,0 +1,7 @@
+RUN: %lldb -b -Q -o "expr 40 + 2" | FileCheck %s
+RUN: %lldb -b -Q -O "expr 40 + 2" | FileCheck %s
+
+CHECK-NOT: expr
+CHECK-NOT: lldb
+CHECK-NOT: source
+CHECK: 42

lldb/tools/driver/Driver.cpp

@@ -609,6 +609,7 @@ int Driver::MainLoop() {
     options.SetSpawnThread(false);
     options.SetStopOnError(true);
     options.SetStopOnCrash(m_option_data.m_batch);
+    options.SetEchoCommands(!m_option_data.m_source_quietly);
 
     SBCommandInterpreterRunResult results =
         m_debugger.RunCommandInterpreter(options);

lldb/tools/driver/Options.td

@@ -110,7 +110,7 @@ def: Flag<["-"], "b">,
   Group<grp_command>;
 
 def source_quietly: F<"source-quietly">,
-  HelpText<"Tells the debugger to execute this one-line lldb command before any file has been loaded.">,
+  HelpText<"Tells the debugger not to echo commands while sourcing files or one-line commands provided on the command line.">,
   Group<grp_command>;
 def: Flag<["-"], "Q">,
   Alias<source_quietly>,