implement Copy command

[matiasinsaurralde]

First attempt at implementing Copy command (#241), still need to polish some stuff

[alicebob]

Hi,

thanks!, looks good in general. You'll also want to add some tests to ./integration/generic_test.go, which will likely help you to get the error cases correctly.

[matiasinsaurralde]

Hi,

thanks!, looks good in general. You'll also want to add some tests to ./integration/generic_test.go, which will likely help you to get the error cases correctly.

Great, I will look into that during the week.

Thanks for the feedback.

[matiasinsaurralde]

@alicebob I've added initial test cases which should cover the most basic functionality of the copy command. Have also fixed the output checks in both integration and standard tests as this command doesn't really return errors (like no such key) but just simple integer values for each scenario.

I believe that a separate PR could be prepared for supporting the two optional arguments (db and replace), as described here.

Test output:

% cd integration ; go test . -v -tags 'int' -run Copy
=== RUN   TestCopy
--- PASS: TestCopy (0.02s)
PASS
ok  	github.com/alicebob/miniredis/v2/integration	(cached)
% redis-cli info | grep redis_version
redis_version:6.2.6
% go test . -v -run Copy
=== RUN   TestCopy
=== RUN   TestCopy/nonexistent_key
=== RUN   TestCopy/existing_key
--- PASS: TestCopy (0.00s)
    --- PASS: TestCopy/nonexistent_key (0.00s)
    --- PASS: TestCopy/existing_key (0.00s)
PASS
ok  	github.com/alicebob/miniredis/v2	(cached)

[alicebob]

thanks! I'll have a look soon.

[alicebob]

ah, I forgot, can you squash the commits? That's easier for me to merge them later. Thanks!

[matiasinsaurralde]

@alicebob Squashed 👍

[rockitbaby]

Thank you for contributing @matiasinsaurralde – this looks good to me!
Minor: Do not forget to add COPY to the list of implemented commands in README.md

[matiasinsaurralde]

@rockitbaby Thanks for the suggestion, have updated the README

[alicebob]

Hi! thanks for the last fix. I was just finishing this. I've added support for DB and REPLACE in #244. But the DB argument wouldn't work with the existing implementation, so I've changed the m.Copy() to be m.Copy(0, "from", 0, "to") (or whichever database IDs you want). Bit verbose, but at least it's clear.
There was a serious bug that it didn't copy the contents of keys (such as hashes), but only the pointer, which means that changing the old key would also change the copy. That's also fixed.

[matiasinsaurralde]

@alicebob Thanks, looking good

[alicebob]

thanks! it's merged in master