Add documentation about parameter and return value

include/git2/commit.h

@@ -479,6 +479,7 @@ GIT_EXTERN(int) git_commit_create_buffer(
  * to the commit and write it into the given repository.
  *
  * @param out the resulting commit id
+ * @param repository the repository where to create the commit.
  * @param commit_content the content of the unsigned commit object
  * @param signature the signature to add to the commit. Leave `NULL`
  * to create a commit without adding a signature field.
@@ -499,6 +500,7 @@ GIT_EXTERN(int) git_commit_create_with_signature(
  *
  * @param out Pointer to store the copy of the commit
  * @param source Original commit to copy
+ * @return 0
  */
 GIT_EXTERN(int) git_commit_dup(git_commit **out, git_commit *source);