obsolete: flip `obstore.successors` and `obsolete.precursors`
People were confused by the fact `obstore.precursors` contained marker allowing
to find "precursors" and vice-versa.
This changeset changes their meaning to:
- precursors[x] -> set(markers on precursors edges of x)
- successors[x] -> set(markers on successors edges of x)
Some documentation is added to clarify the situation.
$ "$TESTDIR/hghave" symlink || exit 80
$ 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
$ "$TESTDIR/readlink.py" dangling
dangling -> nothing
tar
$ cd "$origdir"
$ tar xf archive.tar
$ cd tar
$ "$TESTDIR/readlink.py" dangling
dangling -> nothing
zip
$ cd "$origdir"
$ unzip archive.zip > /dev/null
$ cd zip
$ "$TESTDIR/readlink.py" dangling
dangling -> nothing
$ cd ..