branchcache: add a "pure topological head" fast path
In a narrow but actually quick common case, all topological heads are all on
the same branch and all open. In this case, computing the branch map is very
simple. We can quickly detect situation where this situation will not change.
So we update the V3 format to be able to express this situation and upgrade the
update code to detect we remains in that mode.
The branch cache is populated with the actual value when the branch map is
accessed, but the update_disk method can do the update without needing to
populate it.
# Extract version number into 4 parts, some of which may be empty:
#
# version: the numeric part of the most recent tag. Will always look like 1.3.
#
# type: if an rc build, "rc", otherwise empty
#
# distance: the distance from the nearest tag, or empty if built from a tag
#
# node: the node|short hg was built from, or empty if built from a tag
gethgversion() {
if [ -z "${1+x}" ]; then
python="python3"
else
python="$1"
fi
export HGRCPATH=
export HGPLAIN=
make cleanbutpackages PYTHON=$python
make local PURE=--pure PYTHON=$python
HG="$PWD/hg"
$python "$HG" version > /dev/null || { echo 'abort: hg version failed!'; exit 1 ; }
hgversion=`LANGUAGE=C $python "$HG" version | sed -ne 's/.*(version \(.*\))$/\1/p'`
if echo $hgversion | grep + > /dev/null 2>&1 ; then
tmp=`echo $hgversion | cut -d+ -f 2`
hgversion=`echo $hgversion | cut -d+ -f 1`
distance=`echo $tmp | cut -d- -f 1`
node=`echo $tmp | cut -d- -f 2`
else
distance=''
node=''
fi
if echo $hgversion | grep -E -- '[0-9]\.[0-9](\.[0-9])?rc' > /dev/null 2>&1; then
version=`echo $hgversion | cut -d'r' -f1`
type="rc`echo $hgversion | cut -d'c' -f2-`"
else
version=$hgversion
type=''
fi
}