Merge pull request libgit2#4348 from pks-t/pks/win32-hash-memleak

diff: cleanup hash ctx in `git_diff_patchid`

Author: ethomson

src/diff.c

@@ -517,5 +517,6 @@ int git_diff_patchid(git_oid *out, git_diff *diff, git_diff_patchid_options *opt
 	git_oid_cpy(out, &args.result);
 
 out:
+	git_hash_ctx_cleanup(&args.ctx);
 	return error;
 }