revlog: drop cache after use to save memory footprint
If we reconstruct back to back large versions, we need to drop the cache first to avoid doubling memory usage.
#!/bin/sh
hg init a
cd a
hg init b
echo x > b/x
echo '# should print nothing'
hg add b
hg st
echo '# should fail'
hg st b/x
hg add b/x
echo '# should fail'
hg add b b/x
hg st
echo '# should arguably print nothing'
hg st b
echo a > a
hg ci -Ama a
echo '# should fail'
hg mv a b
hg st