Changes:
1. Adds the `redis.acl_check_cmd()` api to lua scripts. It can be used to check if the
current user has permissions to execute a given command. The new function receives
the command to check as an argument exactly like `redis.call()` receives the command
to execute as an argument.
2. In the PR I unified the code used to convert lua arguments to redis argv arguments from
both the new `redis.acl_check_cmd()` API and the `redis.[p]call()` API. This cleans up
potential duplicate code.
3. While doing the refactoring in 2 I noticed there's an optimization to reduce allocation calls
when parsing lua arguments into an `argv` array in the `redis.[p]call()` implementation.
These optimizations were introduced years ago in 48c49c485155ba9e4a7851fd1644c171674c6f0f
and 4f686555ce962e6632235d824512ea8fdeda003c. It is unclear why this was added.
The original commit message claims a 4% performance increase which I couldn't recreate
and might not be worth it even if it did recreate. This PR removes that optimization.
Following are details of the benchmark I did that couldn't reveal any performance
improvements due to this optimization:
```
benchmark 1: src/redis-benchmark -P 500 -n 10000000 eval 'return redis.call("ping")' 0
benchmark 2: src/redis-benchmark -P 500 -r 1000 -n 1000000 eval 'return redis.call("mset","k1__rand_int__","v1__rand_int__","k2__rand_int__","v2__rand_int__","k3__rand_int__","v3__rand_int__","k4__rand_int__","v4__rand_int__")' 0
benchmark 3: src/redis-benchmark -P 500 -r 1000 -n 100000 eval "for i=1,100,1 do redis.call('set','kk'..i,'vv'..__rand_int__) end return redis.call('get','kk5')" 0
benchmark 4: src/redis-benchmark -P 500 -r 1000 -n 1000000 eval 'return redis.call("mset","k1__rand_int__","v1__rand_int__","k2__rand_int__","v2__rand_int__","k3__rand_int__","v3__rand_int__","k4__rand_int__","v4__rand_int__xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx")'
```
I ran the benchmark on this branch with and without commit 68b71680a4d3bb8f0509e06578a9f15d05b92a47
Results in requests per second:
cmd | without optimization | without optimization 2nd run | with original optimization | with original optimization 2nd run
-- | -- | -- | -- | --
1 | 461233.34 | 477395.31 | 471098.16 | 469946.91
2 | 34774.14 | 35469.8 | 35149.38 | 34464.93
3 | 6390.59 | 6281.41 | 6146.28 | 6464.12
4 | 28005.71 | | 27965.77 |
As you can see, different use cases showed identical or negligible performance differences.
So finally I decided to chuck the original optimization and simplify the code.
9dfeda58ed