-# git read-tree manual page says this is the proper way to fully repopulate
-# the working tree.
-git config core.sparseCheckout true
-rm -f "$GIT_DIR/info/sparse-checkout"
-echo "/*" > "$GIT_DIR/info/sparse-checkout"
-git read-tree -mu HEAD
-git config core.sparseCheckout false
+# Verify if the current branch is valid before updating the working tree.
+# This avoids errors with empty repositories which would only confuse the
+# user.
+if git rev-parse --verify HEAD >/dev/null 2>&1;
+then
+ # git read-tree manual page says this is the proper way to fully repopulate
+ # the working tree.
+ git config core.sparseCheckout true
+ rm -f "$GIT_DIR/info/sparse-checkout"
+ echo "/*" > "$GIT_DIR/info/sparse-checkout"
+ RET=0
+ git read-tree -mu HEAD || RET=$?
+ git config core.sparseCheckout false
+
+ # if updating the working tree failed exit the whole vcsh process to prevent
+ # entering the repository.
+ if [ $RET -ne 0 ];
+ then
+ echo "Fix the problems before entering the repository." 1>&2
+ kill -- -$PPID
+ fi
+fi