apply_patches CMakeFunction shouldn't checkout existing branch

[PawelJurek]

Function "apply_patches" checks out the branch, where patches are applied if it already exists:

opencl-clang/cmake/modules/CMakeFunctions.cmake

Line 71 in 51fd5b9

else() # The target branch already exists

I think the logic here might lead to unexpected issues, e.g. if you download new opencl-clang commit, where a new patch is introduced, it won't be applied if the branch is not manually deleted.

Maybe the function should delete the branch at first step?

[wenju-he]

yes I think the logic needs to be refined so that new patch will be applied.

[haonanya]

Besides, function that checks if the the patch is present in current local branch https://github.com/intel/opencl-clang/blob/ocl-open-100/cmake/modules/CMakeFunctions.cmake#L52 also doesn't work. It seems that commit id from one patch generated by git format-patch is always not same as the result from git am, see example from https://stackoverflow.com/questions/8550400/should-git-apply-or-git-am-come-up-with-the-same-hash.