fixes for bootstrap.sh for upgrading

* `git fetch` wasn't done right for shallow clones
* the test for whether mailinabox has already been cloned wasn't looking at the right directory if the script was not run from $HOME

setup/bootstrap.sh

@@ -17,12 +17,12 @@ if [[ $EUID -ne 0 ]]; then
 fi
 
 # Clone the Mail-in-a-Box repository if it doesn't exist.
-if [ ! -d mailinabox ]; then
+if [ ! -d $HOME/mailinabox ]; then
 	echo Installing git . . .
 	DEBIAN_FRONTEND=noninteractive apt-get -q -q install -y git < /dev/null
 	echo
 
-	echo Downloading Mail-in-a-Box . . .
+	echo Downloading Mail-in-a-Box $TAG. . .
 	git clone \
 		-b $TAG --depth 1 \
 		https://github.com/mail-in-a-box/mailinabox \
@@ -38,7 +38,7 @@ cd $HOME/mailinabox
 # Update it.
 if [ "$TAG" != `git describe` ]; then
 	echo Updating Mail-in-a-Box to $TAG . . .
-	git fetch
+	git fetch --depth 1 --force --prune origin tag $TAG
 	if ! git checkout -q $TAG; then
 		echo "Update failed. Did you modify something in `pwd`?"
 		exit