Move various files that don't need to be in basic/ to shared/

This doesn't have much effect on the final build, because we link libbasic.a
into libsystemd-shared.so, so in the end, all the object built from basic/
end up in libsystemd-shared. And when the static library is linked into binaries,
any objects that are included in it but are not used are trimmed. Hence, the
size of output artifacts doesn't change:

$ du -sb /var/tmp/inst*
54181861	/var/tmp/inst1    (old)
54207441	/var/tmp/inst1s   (old split-usr)
54182477	/var/tmp/inst2    (new)
54208041	/var/tmp/inst2s   (new split-usr)

(The negligible change in size is because libsystemd-shared.so is bigger
by a few hundred bytes. I guess it's because symbols are named differently
or something like that.)

The effect is on the build process, in particular partial builds. This change
effectively moves the requirements on some build steps toward the leaves of the
dependency tree. Two effects:
- when building items that do not depend on libsystemd-shared, we
  build less stuff for libbasic.a (which wouldn't be used anyway,
  so it's a net win).
- when building items that do depend on libshared, we reduce libbasic.a as a
  synchronization point, possibly allowing better parallelism.

Method:
1. copy list of .h files from src/basic/meson.build to /tmp/basic
2. $ for i in $(grep '.h$' /tmp/basic); do echo $i; git --no-pager grep "include \"$i\"" src/basic/ 'src/lib*' 'src/nss-*' 'src/journal/sd-journal.c' |grep -v "${i%.h}.c";echo ;done | less

1 files changed, 130 insertions, 0 deletions

diff --git a/src/shared/verbs.c b/src/shared/verbs.c
new file mode 100644
index 0000000000..f68c2bae08
--- /dev/null
+++ b/src/shared/verbs.c
@@ -0,0 +1,130 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <errno.h>
+#include <getopt.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <string.h>
+
+#include "env-util.h"
+#include "log.h"
+#include "macro.h"
+#include "process-util.h"
+#include "string-util.h"
+#include "verbs.h"
+#include "virt.h"
+
+/* Wraps running_in_chroot() which is used in various places, but also adds an environment variable check so external
+ * processes can reliably force this on.
+ */
+bool running_in_chroot_or_offline(void) {
+        int r;
+
+        /* Added to support use cases like rpm-ostree, where from %post scripts we only want to execute "preset", but
+         * not "start"/"restart" for example.
+         *
+         * See docs/ENVIRONMENT.md for docs.
+         */
+        r = getenv_bool("SYSTEMD_OFFLINE");
+        if (r < 0 && r != -ENXIO)
+                log_debug_errno(r, "Failed to parse $SYSTEMD_OFFLINE: %m");
+        else if (r >= 0)
+                return r > 0;
+
+        /* We've had this condition check for a long time which basically checks for legacy chroot case like Fedora's
+         * "mock", which is used for package builds.  We don't want to try to start systemd services there, since
+         * without --new-chroot we don't even have systemd running, and even if we did, adding a concept of background
+         * daemons to builds would be an enormous change, requiring considering things like how the journal output is
+         * handled, etc.  And there's really not a use case today for a build talking to a service.
+         *
+         * Note this call itself also looks for a different variable SYSTEMD_IGNORE_CHROOT=1.
+         */
+        r = running_in_chroot();
+        if (r < 0)
+                log_debug_errno(r, "running_in_chroot(): %m");
+
+        return r > 0;
+}
+
+int dispatch_verb(int argc, char *argv[], const Verb verbs[], void *userdata) {
+        const Verb *verb;
+        const char *name;
+        unsigned i;
+        int left, r;
+
+        assert(verbs);
+        assert(verbs[0].dispatch);
+        assert(argc >= 0);
+        assert(argv);
+        assert(argc >= optind);
+
+        left = argc - optind;
+        argv += optind;
+        optind = 0;
+        name = argv[0];
+
+        for (i = 0;; i++) {
+                bool found;
+
+                /* At the end of the list? */
+                if (!verbs[i].dispatch) {
+                        if (name)
+                                log_error("Unknown operation %s.", name);
+                        else
+                                log_error("Requires operation parameter.");
+                        return -EINVAL;
+                }
+
+                if (name)
+                        found = streq(name, verbs[i].verb);
+                else
+                        found = verbs[i].flags & VERB_DEFAULT;
+
+                if (found) {
+                        verb = &verbs[i];
+                        break;
+                }
+        }
+
+        assert(verb);
+
+        if (!name)
+                left = 1;
+
+        if (verb->min_args != VERB_ANY &&
+            (unsigned) left < verb->min_args) {
+                log_error("Too few arguments.");
+                return -EINVAL;
+        }
+
+        if (verb->max_args != VERB_ANY &&
+            (unsigned) left > verb->max_args) {
+                log_error("Too many arguments.");
+                return -EINVAL;
+        }
+
+        if ((verb->flags & VERB_ONLINE_ONLY) && running_in_chroot_or_offline()) {
+                if (name)
+                        log_info("Running in chroot, ignoring request: %s", name);
+                else
+                        log_info("Running in chroot, ignoring request.");
+                return 0;
+        }
+
+        if (verb->flags & VERB_MUST_BE_ROOT) {
+                r = must_be_root();
+                if (r < 0)
+                        return r;
+        }
+
+        if (name)
+                return verb->dispatch(left, argv, userdata);
+        else {
+                char* fake[2] = {
+                        (char*) verb->verb,
+                        NULL
+                };
+
+                return verb->dispatch(1, fake, userdata);
+        }
+}