Properly document jgvariant-ostree.

Change-Id: I0aa3b1df512ef99d0e25d73efdd34a1b488e7d0d
diff --git a/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/FileMeta.java b/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/FileMeta.java
index 19e0677..2786ce9 100644
--- a/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/FileMeta.java
+++ b/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/FileMeta.java
@@ -7,7 +7,15 @@
 /**
  * Permission bits and extended attributes for a file.
  *
+ * <p>Stored in a POSIX extended attribute on the corresponding {@link ObjectType#FILE} object in
+ * repositories in “bare-user” format.
+ *
  * <p>Reference: {@code ostree-core.h#OSTREE_FILEMETA_GVARIANT_STRING}
+ *
+ * @param uid the user ID that owns the file.
+ * @param gid the group ID that owns the file.
+ * @param mode the POSIX permission bits.
+ * @param xattrs POSIX extended attributes.
  */
 public record FileMeta(int uid, int gid, int mode, List<Xattr> xattrs) {
 
@@ -19,6 +27,11 @@
           Decoder.ofInt().withByteOrder(ByteOrder.BIG_ENDIAN),
           Decoder.ofArray(Xattr.decoder()));
 
+  /**
+   * Acquires a {@link Decoder} for the enclosing type.
+   *
+   * @return a possibly shared {@link Decoder}.
+   */
   public static Decoder<FileMeta> decoder() {
     return DECODER;
   }