feat(shell): add hm-override script

modules/hm/shell/misc.nix

@@ -10,6 +10,77 @@
       dig
       lsof
       trok
+
+      (writeShellScriptBin "hm-override" ''
+        #!/usr/bin/env bash
+
+        set -euo pipefail
+
+        usage() {
+          echo "Usage:"
+          echo "  $0 <filename>              Override symlink"
+          echo "  $0 <filename> --restore    Restore symlink"
+          echo "  $0 <filename> -r           Restore symlink"
+          exit 1
+        }
+
+        if [[ $# -lt 1 || $# -gt 2 ]]; then
+          usage
+        fi
+
+        FILE="$1"
+        LINK_BACKUP="''${FILE}.backup-link"
+
+        # Restore
+        if [[ "''${2:-}" == "--restore" || "''${2:-}" == "-r" ]]; then
+          if [[ ! -f "$LINK_BACKUP" ]]; then
+            echo "Error: no backup symlink found: $LINK_BACKUP"
+            exit 1
+          fi
+
+          TARGET="$(cat "$LINK_BACKUP")"
+
+          # Remove the temporary override.
+          rm -f "$FILE"
+
+          # Restore the original symlink.
+          ln -s "$TARGET" "$FILE"
+
+          # Remove the temporary symlink target backup.
+          rm "$LINK_BACKUP"
+
+          echo "Restored: $FILE -> $TARGET"
+          exit 0
+        fi
+
+        # Override mode
+        if [[ ! -L "$FILE" ]]; then
+          echo "Error: $FILE is not a symlink"
+          exit 1
+        fi
+
+        if [[ -e "$LINK_BACKUP" ]]; then
+          echo "Error: backup already exists: $LINK_BACKUP"
+          echo "Restore the existing override before running again."
+          exit 1
+        fi
+
+        # Remember the original symlink target.
+        TARGET="$(readlink "$FILE")"
+        printf '%s\n' "$TARGET" > "$LINK_BACKUP"
+
+        # Copy the contents before removing the symlink.
+        cp "$FILE" "$FILE.tmp"
+
+        # Replace the symlink with a regular writable file.
+        rm "$FILE"
+        mv "$FILE.tmp" "$FILE"
+
+        chmod u+w "$FILE"
+
+        echo "Overridden: $FILE"
+        echo "Original:   $FILE -> $TARGET"
+      '')
     ];
   };
 }