If profiling is enabled via global/user config (as far as I can tell, this
doesn't affect use of the --profile flag, but it probably does affect --config
profiling.enabled=1), then the profiling data can be *cumulative* for the
lifetime of the chg process.
This leads to some "interesting" results where hg claims the walltime is
something like 200s on a command that took only a second or two to run. Worse,
however, is that with at least some profilers (such as the default "stat"
profiler), this can cause a large slowdown while generating the profiler output.