[ci] fix CMakeLint errors related to function naming case

[StrikerRUS]

Contributes to #4602.

Use lower case for all functions to fix all readability/mixedcase errors.

There are false alerts for readability/wonkycas in some built-in CMake functions, e.g.

LightGBM/CMakeLists.txt

Line 501 in 6cbb358

FetchContent_Declare(

LightGBM/CMakeLists.txt

Line 506 in 6cbb358

FetchContent_MakeAvailable(googletest)

https://cmake.org/cmake/help/latest/module/FetchContent.html

So the option only is to not check readability/wonkycase type of errors. Because there is no NOLINT directive in the cmakelint package like it is in the cpplint package 🙁 .

[jameslamb]

There are false alerts for readability/wonkycas in some built-in CMake

@StrikerRUS I don't think we need to filter out the readability/wonkycase warnings.

I think the mixed-case commands you mentioned can be lower-cased. I tried that tonight and was able to run the tests successfully.

# lowercase commands
sed -i.bak -e "s/FetchContent_Declare/fetchcontent_declare/" CMakeLists.txt
sed -i.bak -e "s/FetchContent_MakeAvailable/fetchcontent_makeavailable/" CMakeLists.txt

# run tests
rm -rf build/
mkdir build/
cmake -DBUILD_CPP_TEST=ON -DUSE_OPENMP=OFF -DUSE_DEBUG=ON ..
make testlightgbm -j4
./../testlightgbm

That's consistent with https://cmake.org/cmake/help/latest/manual/cmake-language.7.html#command-invocations, which says

Command names are case-insensitive

[StrikerRUS]

Hmmm, thanks for clarifying that those commands can be lower-cased. But in the official docs they are mixed-cased. Don't you think we should stick to the official (which I personally consider as a recommended) CMake naming style but not to cmakelint one?

[jameslamb]

Don't you think we should stick to the official (which I personally consider as a recommended) CMake naming style but not to cmakelint one

Personally, I'd prefer to use the lower-cased one so cmakelint can continue to do the review work for us of telling contributors to lowercase commands.

Otherwise, we'll have to write comments like "can you please change OPTION() to option() for consistency", "can you please change ADD_DEFINITIONS() to add_definitions()", etc.

[StrikerRUS]

Otherwise, we'll have to write comments like "can you please change OPTION() to option() for consistency", "can you please change ADD_DEFINITIONS() to add_definitions()", etc.

These style issues will produce readability/mixedcase error. So we won't have say anything.
cmakelint will stop catching something like OptIoN() or add_DEFINITIONS(). Do you think this is a common problem we'll face?

[jameslamb]

ohhhhh I understand, yeah ok I am ok with filtering out readability/wonkycase then. Thanks for talking through it with me.

[jameslamb]

Nice work! Just 3 warnings from cmakelint remaining after this!

https://github.com/microsoft/LightGBM/runs/4201144410?check_suite_focus=true

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