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.

basic: re-sort includes My previous patch to only include what we use accidentially placed the added inlcudes in non-sorted order.

basic: include only what we use This is a cleaned up result of running iwyu but without forward declarations on src/basic.

execute: Add new PassEnvironment= directive This directive allows passing environment variables from the system manager to spawned services. Variables in the system manager can be set inside a container by passing `--set-env=...` options to systemd-spawn. Tested with an on-disk test.service unit. Tested using multiple variable names on a single line, with an empty setting to clear the current list of variables, with non-existing variables. Tested using `systemd-run -p PassEnvironment=VARNAME` to confirm it works with transient units. Confirmed that `systemctl show` will display the PassEnvironment settings. Checked that man pages are generated correctly. No regressions in `make check`.

systemctl: add a way to explicitly request client-side unit installing This adds support for a new environment variable SYSTEMCTL_INSTALL_CLIENT_SIDE, that ensures that systemctl executes install operations client-side instead of passing them to PID1. This is useful in debugging situations, but even beyond that. However, we don't want to make it official API, hence let's just make it an undocumented environment variable. Similar, add a second variable, SYSTEMCTL_SKIP_SYSV which allows skipping the SysV chkconfig fall-back if set. This is useful for similar reasons, and exposed as undocumented as environment variable for similar reasons, too.

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

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.

basic: fix env expansion for strings leading with two dollar signs The way to escape a literal dollar sign is to write "$$". But this does not work right if it's at the beginning of the argument. Fix it.

strv: convert strv_split_quotes into a generic strv_split_extract strv_split_extract is to strv_split_quotes as extract_first_word was to unquote_first_word. Now there's extract_first_word for extracting a single argument, extract_many_words for extracting a bounded number of arguments, and strv_split_extract for extracting an arbitrary number of arguments.

util: change unquote_*_word to extract_*_word It now takes a separators argument, which defaults to WHITESPACE if NULL is passed.

build-sys: split internal basic/ library from shared/ basic/ can be used by everything cannot use anything outside of basic/ libsystemd/ can use basic/ cannot use shared/ shared/ can use libsystemd/