`ZDIFF` command discrepancies

[michael-grunder]

Describe the bug

1. ZDIFF ignores the WITHSCORES argument if it is not sent in all caps.
2. Dragonfly's ZDIFF WITHSCORES reply is structurally different from Redis'

To Reproduce
Steps to reproduce the behavior:

1. Add an entry to a zset
2. Run ZDIFF withscores (withscores must not be all-caps)
3. Run ZDIFF WITHSCORES in RESP3 mode

Expected behavior

1. The WITHSCORES argument to be case insensitive.
2. The ZDIFF WITHSCORES reply is structured the same way as Redis does in RESP3 mode.

Environment (please complete the following information):

• OS: Debian GNU/Linux forky/sid x86_64
• Kernel: # Command: Linux hydra 6.1.0-29-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.123-1 (2025-01-02) x86_64 GNU/Linux
• Containerized?: Bare metal, dragonfly db in a container
• Dragonfly Version: df-dev (a4ee2d5)

Reproducible Code Snippet

1. To demonstrate WITHSCORES is case sensitive:

redis-cli -3 zadd zs 1 one
redis-cli -3 echo "no scores"
redis-cli -3 zdiff 1 zs withscores
redis-cli -3 echo "with scores"
redis-cli -3 zdiff 1 zs WITHSCORES

2. Demonstrating the replies structural difference:

Redis:

# In my case Redis is on port 6382
redis-cli zadd zs 1 one && redis-cli -p 6382 -3 zdiff 1 zs withscores
(integer) 0
1) 1) "one"
   2) (double) 1

Dragonfly:

❯ redis-cli zadd zs 1 one && redis-cli -3 zdiff 1 zs WITHSCORES
(integer) 0
1) "one"
2) (double) 1

Additional context
I'm guessing the case-sensitive issue is here:

dragonfly/src/server/zset_family.cc

Line 2321 in a4ee2d5

const bool with_scores = ArgS(args, args.size() - 1) == "WITHSCORES";