discovery: simplify branchmap construction against legacy server
All necessary data to fire a simple revset query are already known. No call to
ancestors are needed. Such ancestors calculation was already done to compute
outgoing.missing.
#!/usr/bin/env python
# Filter output by the progress extension to make it readable in tests
import sys, re
for line in sys.stdin:
line = re.sub(r'\r+[^\n]', lambda m: '\n' + m.group()[-1:], line)
sys.stdout.write(line)
print