#!/bin/bash
set -eou pipefail

# Example:
#   ./workspace-pack-hg-base.sh https://hg.openjdk.java.net/jmc/jmc jmc-jmc

URL=$1
NAME=$2
UPSTREAM_NAME=$NAME-upstream

# Enable aggressive repository format for Mercurial. Cloning the repository into
# this format would take a while. This is mostly convenient for the CI jobs that
# repackage the workspaces, but not for user clones
HG_OPTS="--config=format.generaldelta=1 --config=format.aggressivemergedeltas=1"

# Clone the repository, if it does not exist yet.
if [ ! -d $UPSTREAM_NAME ]; then
  hg $HG_OPTS clone $URL $UPSTREAM_NAME
fi

# Perform the very first pull of the repository. This would already merge some
# metadata using general+aggressive deltas. Make sure repository does not have
# working copy checked up, only the metadata itself.
cd $UPSTREAM_NAME
hg $HG_OPTS pull
hg update null
cd ..

# Perform the *second* clone of the repository. This apparently repackages the
# manifest and metadata to a much more compact form. Make sure working copy is
# not materialized, an that we use the non-local clone that actually rewires 
# metadata. This clone would record the "local" repo as parent, overwrite it
# with the upstream repo URL.
rm -rf $NAME
hg $HG_OPTS clone --pull --uncompressed -U $UPSTREAM_NAME $NAME
echo -e "[paths]\ndefault = $URL" > $NAME/.hg/hgrc	

# Package the repository.
tar -c -f $NAME.tar $NAME

# Finally, compress the whole thing with the max compression available. This 
# probably clashes with Mercurial's own storage compression, and it would be
# interesting to somehow request the metadata compressor to unpack the repository
# internal metadata for this compressor to work on raw stream. That is what 
# "hg bundle" apparently does? We are working with the repository copy itself,
# so we have to be content with whatever compression we can get.
pxz -9 $NAME.tar

# Verification: unpack the resulting tarball and check repository is still fine
rm -rf temp
mkdir -p temp
cd temp
tar xJf ../$NAME.tar.xz
cd $NAME
hg update
hg verify
cd ../../
rm -rf temp

# Cleanup temporary file
rm -rf $NAME