hack-on

#!/usr/bin/env bash
set -euo pipefail

DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )

. "$DIR/common-setup.sh"

REPO="$(echo "$1" | sed 's_/$__')"

if [ ! -d "$REPO" ] ; then
    echo "Error: no such directory: $REPO"
    exit 1
fi

DIFF="$(git -C "$REPO/.." diff HEAD -- "$REPO")"
DIFF_ERR=$?
STATUS="$(git -C "$REPO/.." status --porcelain --ignored "$REPO")"
STATUS_ERR=$?

if [ "$DIFF_ERR" -ne 0 -o "$STATUS_ERR" -ne 0 ] ; then
    >&2 echo "Error: could not determine whether $REPO contains unsaved modifications"
    exit 1
elif [ -n "$DIFF" -o -n "$STATUS" ] ; then
    >&2 echo "$DIFF"
    >&2 echo "$STATUS"
    >&2 echo "Error: $REPO contains unsaved modifications"
    exit 1
fi

if [ -e "$REPO/git.json" ] ; then
    JSON_FILE="$REPO/git.json"
    URL="$(eval "echo $(nix-instantiate $NIXOPTS --eval -E "(builtins.fromJSON (builtins.readFile $REPO/git.json)).url")")"
    REV="$(eval "echo $(nix-instantiate $NIXOPTS --eval -E "(builtins.fromJSON (builtins.readFile $REPO/git.json)).rev")")"
elif [ -e "$REPO/github.json" ] ; then
    JSON_FILE="$REPO/github.json"
    GITHUB_OWNER="$(eval "echo $(nix-instantiate $NIXOPTS --eval -E "(builtins.fromJSON (builtins.readFile $REPO/github.json)).owner")")"
    GITHUB_REPO="$(eval "echo $(nix-instantiate $NIXOPTS --eval -E "(builtins.fromJSON (builtins.readFile $REPO/github.json)).repo")")"
    URL="git://github.com/$GITHUB_OWNER/$GITHUB_REPO"
    REV="$(eval "echo $(nix-instantiate $NIXOPTS --eval -E "(builtins.fromJSON (builtins.readFile $REPO/github.json)).rev")")"
fi

echo "Checking out $URL at revision $REV"

if [ -f "$REPO/default.nix" ] ; then
    rm "$REPO/default.nix"
fi
rm "$JSON_FILE"
rmdir "$REPO"

git clone -n "$URL" "$REPO"
REMOTE_URL="$(git -C "$REPO" config --get remote.origin.url)"
FIXED_REMOTE_URL="$(echo "$REMOTE_URL" | sed 's_^git://github.com/_git@github.com:_')"
if [ "$REMOTE_URL" != "$FIXED_REMOTE_URL" ] ; then
    echo "Changing remote URL from $REMOTE_URL to $FIXED_REMOTE_URL"
    git -C "$REPO" remote set-url origin "$FIXED_REMOTE_URL"
fi
git -C "$REPO" checkout "$REV"

echo
echo "The following remote branches contain this commit:"
git -C "$REPO" branch -r --contains HEAD | sed -n s_origin/__p
echo "You should probably 'git checkout' one of them to get started.  Happy hacking!"