diff --git a/stack.sh b/stack.sh
index 90763de3ab..14bcfb2762 100755
--- a/stack.sh
+++ b/stack.sh
@@ -302,20 +302,31 @@ sudo PIP_DOWNLOAD_CACHE=/var/cache/pip pip install `cat $FILES/pips/*`
 # be owned by the installation user, we create the directory and change the
 # ownership to the proper user.
 function git_clone {
-    # if there is an existing checkout, move it out of the way
-    if [[ "$RECLONE" == "yes" ]]; then
-        # FIXME(ja): if we were smarter we could speed up RECLONE by
-        # using the old git repo as the basis of our new clone...
-        if [ -d $2 ]; then
-            mv $2 /tmp/stack.`date +%s`
-        fi
-    fi
 
-    if [ ! -d $2 ]; then
-        git clone $1 $2
+    GIT_REMOTE=$1
+    GIT_DEST=$2
+    GIT_BRANCH=$3
+
+    # do a full clone only if the directory doesn't exist
+    if [ ! -d $GIT_DEST ]; then
+        git clone $GIT_REMOTE $GIT_DEST
         cd $2
         # This checkout syntax works for both branches and tags
-        git checkout $3
+        git checkout $GIT_BRANCH
+    elif [[ "$RECLONE" == "yes" ]]; then
+        # if it does exist then simulate what clone does if asked to RECLONE
+        cd $GIT_DEST
+        # set the url to pull from and fetch
+        git remote set-url origin $GIT_REMOTE
+        git fetch origin
+        # remove the existing ignored files (like pyc) as they cause breakage
+        # (due to the py files having older timestamps than our pyc, so python
+        # thinks the pyc files are correct using them)
+        sudo git clean -f -d
+        git checkout -f origin/$GIT_BRANCH
+        # a local branch might not exist
+        git branch -D $GIT_BRANCH || true
+        git checkout -b $GIT_BRANCH
     fi
 }