/* For use with `write_locked_index()`. */
#define COMMIT_LOCK (1 << 0)
+#define SKIP_IF_UNCHANGED (1 << 1)
/*
* Write the index while holding an already-taken lock. Close the lock,
* With `COMMIT_LOCK`, the lock is always committed or rolled back.
* Without it, the lock is closed, but neither committed nor rolled
* back.
+ *
+ * If `SKIP_IF_UNCHANGED` is given and the index is unchanged, nothing
+ * is written (and the lock is rolled back if `COMMIT_LOCK` is given).
*/
extern int write_locked_index(struct index_state *, struct lock_file *lock, unsigned flags);