streamclone: stop listing files for entries that have no volatile files
This will save a lot of python related time.
This significantly boost performance. The following number comes from a large
private repository using perf::stream-locked-section:
base-line: 35.04 seconds
prev-change: 24.51 seconds (-30%)
prev-change: 20.88 seconds (-40%)
prev-change: 14.22 seconds (-60%)
this-change: 11.58 seconds (-67% from baseline; -18% from prev)
import os
if os.environ.get('COVERAGE_PROCESS_START'):
try:
import coverage
import uuid
covpath = os.path.join(
os.environ['COVERAGE_DIR'], 'cov.%s' % uuid.uuid1()
)
cov = coverage.coverage(data_file=covpath, auto_data=True)
cov._warn_no_data = False
cov._warn_unimported_source = False
cov.start()
except ImportError:
pass