There is a bug with the PKGFILE which is too aggressive copying files with names containing Kconfig.
Consequence is upon install attempt:
error: failed to commit transaction (conflicting files) /usr/lib/modules/4.4.0-1-ARCH/build/Documentation/kbuild/Kconfig.recursion-issue-01 exists in both 'linux-docs' and 'linux-headers' /usr/lib/modules/4.4.0-1-ARCH/build/Documentation/kbuild/Kconfig.recursion-issue-02 exists in both 'linux-docs' and 'linux-headers' /usr/lib/modules/4.4.0-1-ARCH/build/Documentation/kbuild/Kconfig.select-break exists in both 'linux-docs' and 'linux-headers' Errors occurred, no packages were upgraded.
A "dumb" fix is to remove the duplicate by adding a line to PKGFILE something like:
Work around for users is just to ignore the bad package until its fixed:
pacman -Syu --ignore linux-docs
FYI - same problem with linux-docs-4.4-2-x86_64 package.
Also FYI: https://bugs.archlinux.org/task/47753
Fixed in 4.4-3 - thank you Tobias!