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)
#require symlink
$ origdir=`pwd`
$ hg init repo
$ cd repo
$ ln -s nothing dangling
avoid tar warnings about old timestamp
$ hg ci -d '2000-01-01 00:00:00 +0000' -qAm 'add symlink'
$ hg archive -t files ../archive
$ hg archive -t tar -p tar ../archive.tar
$ hg archive -t zip -p zip ../archive.zip
files
$ cd "$origdir"
$ cd archive
$ readlink.py dangling
dangling -> nothing
tar
$ cd "$origdir"
$ tar xf archive.tar
$ cd tar
$ readlink.py dangling
dangling -> nothing
#if unziplinks
zip
$ cd "$origdir"
$ unzip archive.zip > /dev/null 2>&1
$ cd zip
$ readlink.py dangling
dangling -> nothing
#endif
$ cd ..