Add --silent, remap verbosity 0 to 1 while building modules unless silent

Failed that, we may have long periods of seemingly nothing happening (e.g.,
during implicit bdep sync) while we quietly update the module, which may look
like things have hung up.

1 files changed, 6 insertions, 2 deletions

diff --git a/libbuild2/diagnostics.hxx b/libbuild2/diagnostics.hxx
index 5d69132..26f602a 100644
--- a/libbuild2/diagnostics.hxx
+++ b/libbuild2/diagnostics.hxx
@@ -49,7 +49,7 @@ namespace build2
     print_process (args.data (), n != 0 ? n : args.size ());
   }
 
-  // Program verbosity level (-v/--verbose).
+  // Program verbosity level (-v/--verbose plus --silent).
   //
   // 0 - disabled
   // 1 - high-level information messages
@@ -59,13 +59,17 @@ namespace build2
   // 5 - information helpful to the developer
   // 6 - even more detailed information
   //
+  // If silent is true, then the level must be 0 (silent is level 0 that
+  // cannot be relaxed in certain contexts).
+  //
   // While uint8 is more than enough, use uint16 for the ease of printing.
   //
 
   // Forward-declarated in <libbuild2/utility.hxx>.
   //
+  // const uint16_t verb_never = 7;
   // extern uint16_t verb;
-  // const  uint16_t verb_never = 7;
+  // extern bool silent;
 
   template <typename F> inline void l1 (const F& f) {if (verb >= 1) f ();}
   template <typename F> inline void l2 (const F& f) {if (verb >= 2) f ();}