feat: build libsurvive script; common clone or pull script

scripts/_clone_or_pull.sh

@@ -0,0 +1,31 @@
+#!/bin/bash
+
+# exit on error
+# echo commands
+set -ev
+
+GIT_URL=$1
+REPO_DIR=$2
+
+_usage() {
+    echo "Usage: $0 GIT_URL REPO_DIR"
+    exit 1
+}
+
+if [[ -z $REPO_DIR ]]; then
+    _usage
+fi
+
+if [[ -z $GIT_URL ]]; then
+    _usage
+fi
+
+if [[ -d "$REPO_DIR" ]]; then
+    if [[ ! -d "$REPO_DIR/.git" ]]; then
+        echo "Error: $REPO_DIR exists but is not a git repository"
+        exit 1
+    fi
+    git -C "$REPO_DIR" pull
+else
+    git clone "$GIT_URL" "$REPO_DIR"  --recurse-submodules
+fi