MachMessageServer: eliminate argument redundancy

tools/catch_exception_tool.ad

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 27 matching lines @@
 Information about the exception will be appended to 'FILE' instead of the
 standard output stream.
 
 *-m*, *--mach-service*='SERVICE'::
 Check in with the bootstrap server under the name 'SERVICE'. This service name
 may already be reserved with the bootstrap server in cases where this tool is
 started by launchd(8) as a result of a message being sent to a service declared
 in a job’s +MachServices+ dictionary (see launchd.plist(5)). The service name
 may also be completely unknown to the system.
 
-*-n*, *--nonblocking*::
-Don’t wait for an exception to occur if one is not received immediately. In
-nonblocking mode, this tool exits immediately if no exception is received. The
-default mode is blocking.
-
 *-p*, *--persistent*::
 Continue processing exceptions after the first one. The default mode is
 one-shot, where this tool exits after processing the first exception.
 
 *-t*, *--timeout*='TIMEOUT'::
-Run for a maximum of 'TIMEOUT' seconds. This option only has an effect in
-blocking mode (when *--nonblocking* is not specified). In *--persistent* mode,
-'TIMEOUT' applies to the overall duration that this tool will run, not to the
-processing of individual exceptions.
+Run for a maximum of 'TIMEOUT' seconds. Specify +0+ to request non-blocking
+operation, in which the tool exits immediately if no exception is received. In
+*--persistent* mode, 'TIMEOUT' applies to the overall duration that this tool
+will run, not to the processing of individual exceptions. When *--timeout* is
+not specified, this tool will block indefinitely while waiting for an exception.
 
 *--help*::
 Display help and exit.
 
 *--version*::
 Output version information and exit.
 
 == Examples
 
 Run a one-shot blocking exception server registered with the bootstrap server
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 signal SIGILL
 ----
 
 Run an on-demand exception server started by launchd(5) available via the
 bootstrap server under the name +svc+:
 [subs="quotes"]
 ----
 $ *on_demand_service_tool --load --label=catch_exception \
       --mach-service=svc \
       $(which catch_exception_tool) --mach-service=svc \
-      --file=/tmp/out --nonblocking --persistent*
+      --file=/tmp/out --persistent --timeout=0*
 $ *exception_port_tool --set-handler=handler=bootstrap:svc crasher*
 Illegal instruction: 4
 $ *on_demand_service_tool --unload --label=catch_exception*
 $ *cat /tmp/out*
 catch_exception_tool:
 behavior EXCEPTION_DEFAULT|MACH_EXCEPTION_CODES,
 pid 2468, thread 13579, exception EXC_CRASH, codes[2] 0x4200001, 0,
 original exception EXC_BAD_INSTRUCTION, original code[0] 1,
 signal SIGILL
 ----
 
 == Exit Status
 
 *0*::
 Success. In *--persistent* mode with a *--timeout* set, it is considered
 successful if at least one exception was caught when the timer expires.
 
 *1*::
 Failure, with a message printed to the standard error stream.
 
 == See Also
 
 exception_port_tool(1),
 on_demand_service_tool(1)
 
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