Add script to completely reset repos from leftovers

hard_reset_repos.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+set -e
+
+mydir="$(dirname "$(realpath "$0")")"
+
+cd "$mydir"
+
+source ./merge_helpers.sh
+
+# Note: this doesn't delete files starting with a dot,
+# and in particular not the '.git' directory, which we
+# want to keep
+forall_repos bash -c 'rm -rf *'
+forall_repos git reset HEAD --hard