Clarify `repy.py` --logfile option help string

[aaaaalbert]

@vladimir-v-diaz notes that the help string to repy.py's --logfile option omits critical detail.

• The "file name" supplied is really used as a prefix, and the logfile gets a .old or .new suffix to allow for log rotation.
• The logfile is created in the current directory at the time of calling repy.py (I think). It's definitely not using what --cwd says; that option only sets the vessel working dir.

[Ashmita89]

Help string for log file does not include the below information in detail.
For point a.:
ut_repyv2api_commandlineargs.py actively explains the point a in its comments:

# Call Repy. If repy.py mistakingly consumes the --logfile arg, it 
# will create a file named logfile_prefix + ".old" (or .new if .old 
# already existed).
logfile_prefix = "REPY_CALLARG_TEST"
repy_process = portable_popen.Popen([sys.executable, "repy.py", 
    "restrictions.default", program_name, "--logfile", logfile_prefix])

For point b.
repy.py sets the vessel working directory based on --cwd attribute

 #Set Current Working Directory
      if options.cwd:
    os.chdir(options.cwd)

However this is called after the logging attribute is dealt with in repy.py
In this a circular buffer of size =16 KB is used .

   # set up the circular log buffer...
   # Armon: Initialize the circular logger before starting the nanny
   if options.logfile:
    # time to set up the circular logger
    loggerfo = loggingrepy.circular_logger(options.logfile)
    # and redirect err and out there...
    sys.stdout = loggerfo
    sys.stderr = loggerfo
   else:
    #let's make it so that the output (via print) is always flushed
    sys.stdout = loggingrepy.flush_logger(sys.stdout)

Hence,the --cwd option is not used for the log file .

[vladimir-v-diaz]

@Ashmita89
If you haven't done so, would you like to make a pull request for this issue (to ensure the help string is correct)? You have verified the expected behaviour.

The current incorrect help string was a source of frustration when I first tried to locate where Seattle stored his log files.

[aaaaalbert]

@Ashmita89, the unit test you are referring to doesn't test how repy.py utilizes the --logfile option. Instead, it checks that options to repy.py and options to the sandboxed Repy program are indeed handled separately, https://github.com/SeattleTestbed/repy_v2/blob/master/testsV2/ut_repyv2api_commandlineargs.py#L4-L8

In the unit test, the --logfile option is a deliberate attempt to fool repy.py into consuming an argument that is meant for the sandboxed program. It would be dangerous if repy.py consumed that arg, because the user of the sandbox can control it and set it to whatever value.

[Ashmita89]

The unit test log is only referred for understanding the filename created as the comment there gives a more detailed description. It can also be seen in repy.py logfile option uses a circular logger which is more explained in 'loggingrepy_core'
// filenames we'll use for the log data

    self.filenameprefix = fnp

    self.oldfn = fnp+".old"

    self.newfn = fnp+".new"

I think the information from 'loggingrepy_core' would have caused less confusion. We can ignore the part about the unit test file in my previous comment.

[aaaaalbert]

OK, please propose a help string that conveys this information, preferrentially via pull request.