version/update system: version.sh, --update flag, UPDATE_MODULES, auto-detect existing install

lib/version.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+
+OMERON_VERSION_DIR="${OMERON_VERSION_DIR:-$HOME/.local/share/omeron}"
+OMERON_VERSION_FILE="$OMERON_VERSION_DIR/version"
+
+version_read() {
+  if [[ -f "$OMERON_VERSION_FILE" ]]; then
+    source "$OMERON_VERSION_FILE"
+    return 0
+  fi
+  return 1
+}
+
+version_write() {
+  mkdir -p "$OMERON_VERSION_DIR"
+  cat > "$OMERON_VERSION_FILE" <<VERSION
+# Omeron Version File
+OMERON_VERSION=1
+OMERON_INSTALL_DATE="$(date '+%Y-%m-%d %H:%M:%S')"
+OMERON_LAST_UPDATE="$(date '+%Y-%m-%d %H:%M:%S')"
+VERSION
+}
+
+version_update() {
+  mkdir -p "$OMERON_VERSION_DIR"
+  if [[ -f "$OMERON_VERSION_FILE" ]]; then
+    local tmp
+    tmp="$(mktemp)"
+    while IFS= read -r line; do
+      case "$line" in
+        OMERON_LAST_UPDATE=*) printf 'OMERON_LAST_UPDATE="%s"\n' "$(date '+%Y-%m-%d %H:%M:%S')" ;;
+        *) printf '%s\n' "$line" ;;
+      esac
+    done < "$OMERON_VERSION_FILE" > "$tmp"
+    mv "$tmp" "$OMERON_VERSION_FILE"
+  else
+    version_write
+  fi
+}