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.

btrfs: support recursively removing btrfs snapshots

remove unused includes This patch removes includes that are not used. The removals were found with include-what-you-use which checks if any of the symbols from a header is in use.

treewide: no need to negate errno for log_*_errno() It corrrectly handles both positive and negative errno values.

log: add an "error" parameter to all low-level logging calls and intrdouce log_error_errno() as log calls that take error numbers This change has two benefits: - The format string %m will now resolve to the specified error (or to errno if the specified error is 0. This allows getting rid of a ton of strerror() invocations, a function that is not thread-safe. - The specified error can be passed to the journal in the ERRNO= field. Now of course, we just need somebody to convert all cases of this: log_error("Something happened: %s", strerror(-r)); into thus: log_error_errno(-r, "Something happened: %m");

systemctl: automatically turn paths and unescaped unit names into proper unit names This makes sure that systemctl status /home is implicitly translated to: systemctl status /home.mount Similar, /dev/foobar becomes dev-foobar.device. Also, all characters that cannot be part of a unit name are implicitly escaped.

test: test tools should still be in the src/ directory