tree-wide: remove Emacs lines from all files This should be handled fine now by .dir-locals.el, so need to carry that stuff in every file.

util-lib: split out allocation calls into alloc-util.[ch]

util-lib: split out fd-related operations into fd-util.[ch] There are more than enough to deserve their own .c file, hence move them over.

util-lib: split our string related calls from util.[ch] into its own file string-util.[ch] There are more than enough calls doing string manipulations to deserve its own files, hence do something about it. This patch also sorts the #include blocks of all files that needed to be updated, according to the sorting suggestions from CODING_STYLE. Since pretty much every file needs our string manipulation functions this effectively means that most files have sorted #include blocks now. Also touches a few unrelated include files.

sd-login: add new sd_pid_get_cgroup() API This adds a new sd_pid_get_cgroup() call to sd-login which may be used to query the control path of a process. This is useful for programs when making use of delegation units, in order to figure out which subtree has been delegated. In light of the unified control group hierarchy this is finally safe to do, hence let's add a proper API for it, to make it easier to use this.

sd-login: rework error handling Makre sure we always return sensible errors for the various, following the same rules, and document them in a comment in sd-login.c. Also, update all relevant man pages accordingly.

sd-login: improve error handling let's return ENXIO whenever we don't know something rather than ENOENT. ENOENT suggests this was really about a file or directory, while ENXIO is a more generic "not found" indicator.

shared: add formats-util.h

include <poll.h> instead of <sys/poll.h> include-what-you-use automatically does this and it makes finding unnecessary harder to spot. The only content of poll.h is a include of sys/poll.h so should be harmless.

Always prefer our headers to system headers In practice this shouldn't make much difference, but sometimes our headers might be newer, and we want to test them.

Remove unnecessary casts in printfs No functional change expected :)

util: replace close_pipe() with new safe_close_pair() safe_close_pair() is more like safe_close(), except that it handles pairs of fds, and doesn't make and misleading allusion, as it works similarly well for socketpairs() as for pipe()s...

build-sys: move sd-login src/login → src/libsystemd/sd-login After all, it is ultimately linked to libsystems.so anyway, thus belongs there and shares very little with the rest of logind, hence let's move this away.