fix(cli): Suppress trace info in quiet for warnings but do show errors

Author: alerque

core/sile.lua

@@ -47,6 +47,10 @@ SILE.lua_isjit = type(jit) == "table"
 -- @string full_version
 SILE.full_version = string.format("SILE %s (%s)", SILE.version, SILE.lua_isjit and jit.version or _VERSION)
 
+--- Default to verbose mode, can be changed from the CLI or by libraries
+--- @boolean quiet
+SILE.quiet = false
+
 -- Backport of lots of Lua 5.3 features to Lua 5.[12]
 if not SILE.lua_isjit and SILE.lua_version < "5.3" then
    require("compat53")

core/utilities/init.lua

@@ -326,6 +326,7 @@ local _skip_traceback_levels = 2
 -- @tparam string message The error message to give.
 -- @tparam boolean isbug Whether or not hitting this error is expected to be a code bug (as opposed to misakes in user input).
 function utilities.error (message, isbug)
+   SILE.quiet = false
    _skip_traceback_levels = 3
    utilities.warn(message, isbug)
    _skip_traceback_levels = 2
@@ -350,6 +351,9 @@ end
 -- @tparam string message The error message to give.
 -- @tparam boolean isbug Whether or not hitting this warning is expected to be a code bug (as opposed to misakes in user input).
 function utilities.warn (message, isbug)
+   if SILE.quiet then
+      return
+   end
    utilities.msg(message)
    if SILE.traceback or isbug then
       io.stderr:write(" at:\n" .. SILE.traceStack:locationTrace())