fix response for the command that is too long

[ysmolski]

Before the patch, if a client sent too long command, server would
respond by BAD_FORMAT, followed by UNKNOWN_COMMAND. This resulted
in desync between client and server.

This patch adds another state STATE_WANT_ENDLINE,
whose purpose is to drop command line until the EOL is found.
Client can send as big command as he want and server will be able
to skip it and return only one error message: BAD_FORMAT.

Some STATE_* constants were renamed to improve readability.

Fixes #337

[codecov]

Codecov Report

Merging #562 into master will decrease coverage by 0.01%.
The diff coverage is 86.84%.

@@            Coverage Diff             @@
##           master     #562      +/-   ##
==========================================
- Coverage   74.25%   74.23%   -0.02%     
==========================================
  Files          13       13              
  Lines        2288     2302      +14     
==========================================
+ Hits         1699     1709      +10     
- Misses        589      593       +4

[sergeyklay]

@ysmolsky Should we update docs as well?

[ysmolski]

@ysmolsky Should we update docs as well?

Docs mention that already, but expanding it a little would not hurt I guess.
https://github.com/beanstalkd/beanstalkd/blob/master/doc/protocol.txt#L44

[ysmolski]

I have fixed the protocol regarding why BAD_FORMAT may be returned.

[thoro]

@ysmolsky Is it on purpose you added a printf for each command that is executed?

https://github.com/beanstalkd/beanstalkd/pull/562/files#diff-5b9219f6cd269a2c85dc83291ca314a4R1288

[ysmolski]

Oh wow! Thanks for spotting this. I am not sure how it got there, but it was not an intention.

[tomponline]

@ysmolsky maybe we should do another release with all of the fixes you've added since the last one?

[ysmolski]

Yes, that would be awesome. Last release was almost 1 year ago...