Exclude 'flatten' file from coverage by default

[yngvar-antonsson]

tarantool/crud produce 'flatten' file while flattening.

crud.insert_object('space', obj)

.rocks/bin/luatest integration_api --coverage
.rocks/bin/luacov .
Couldn't open flatten: No such file or directory

I propose to exclude it from coverage collection by default:

exclude = {
	'flatten',
}

[Totktonada]

tarantool/crud does not create any temporary files. I think you're about the following code:

flatten_func = assert(load(code, '@flatten', 't', env))

https://github.com/tarantool/crud/blob/5e8c91e39bd608804e0ab85989a537dfd63ec7bf/crud/common/utils.lua#L116

See lunarmodules/luacov#55 (comment).

It seems, we should not use @ here. I guess that the best options is to leave it nil to make equal to code, see docs here and here.

[Totktonada]

Filed tarantool/crud#249 against crud.

[ylobankov]

Looks like not a luatest issue. So closing it. Feel free to reopen if it is related to luatest.