Split redis_cmd.cc to multiple files by category

[PragmaTwice]

It closes #1138.

Current file structure in src/commands:

├── command_parser.h
├── redis_cmd_bit.cc
├── redis_cmd.cc
├── redis_cmd_cluster.cc
├── redis_cmd_error.h
├── redis_cmd_geo.cc
├── redis_cmd.h
├── redis_cmd_hash.cc
├── redis_cmd_key.cc
├── redis_cmd_list.cc
├── redis_cmd_pubsub.cc
├── redis_cmd_replication.cc
├── redis_cmd_script.cc
├── redis_cmd_server.cc
├── redis_cmd_set.cc
├── redis_cmd_sortedint.cc
├── redis_cmd_stream.cc
├── redis_cmd_string.cc
├── redis_cmd_txn.cc
├── redis_cmd_zset.cc
├── scan_util.h
└── ttl_util.h

[git-hulk]

LGTM, love this pr.

[caipengbo]

Isn't the redis_cmd_ prefix a bit redundant?

[PragmaTwice]

Isn't the redis_cmd_ prefix a bit redundant?

I am considering cmd_*, since there are other source files in this directory.

[PragmaTwice]

Though, the current one is acceptable for me.

[caipengbo]

How about dropping the prefix?

[PragmaTwice]

How about dropping the prefix?

I think the prefix can make them more distinguishing than other source files (in this dir) in alphabetical order, e.g.

a  (cmd)
b
c  (cmd)
d
e  (cmd)

than

b
cmd_a
cmd_c
cmd_e
d

[PragmaTwice]

@caipengbo @Hulk I did some rename in cd17abf:

scan_util.h -> scan_base.h
redis_cmd.{h|cc} -> commander.{h|cc}
redis_cmd_*.{h|cc} -> cmd_*.{h|cc}
redis_cmd_error.h -> error_constants.h

[torwig]

@PragmaTwice Great job!

[PragmaTwice]

Thanks all. Merging...