nspawn: split out VolatileMode definitions

This moves the VolatileMode enum and its helper functions to src/shared/. This
is useful to then reuse them to implement systemd.volatile= in a later commit.

src/nspawn/nspawn-mount.c

@@ -1349,21 +1349,3 @@ fail:
         (void) rmdir(template);
         return r;
 }
-
-VolatileMode volatile_mode_from_string(const char *s) {
-        int b;
-
-        if (isempty(s))
-                return _VOLATILE_MODE_INVALID;
-
-        b = parse_boolean(s);
-        if (b > 0)
-                return VOLATILE_YES;
-        if (b == 0)
-                return VOLATILE_NO;
-
-        if (streq(s, "state"))
-                return VOLATILE_STATE;
-
-        return _VOLATILE_MODE_INVALID;
-}

src/nspawn/nspawn-mount.h

@@ -22,6 +22,7 @@
 #include <stdbool.h>
 
 #include "cgroup-util.h"
+#include "volatile-util.h"
 
 typedef enum MountSettingsMask {
         MOUNT_FATAL              = 1 << 0, /* if set, a mount error is considered fatal */
@@ -32,14 +33,6 @@ typedef enum MountSettingsMask {
                                               Works only if MOUNT_APPLY_APIVFS_RO is also set. */
 } MountSettingsMask;
 
-typedef enum VolatileMode {
-        VOLATILE_NO,
-        VOLATILE_YES,
-        VOLATILE_STATE,
-        _VOLATILE_MODE_MAX,
-        _VOLATILE_MODE_INVALID = -1
-} VolatileMode;
-
 typedef enum CustomMountType {
         CUSTOM_MOUNT_BIND,
         CUSTOM_MOUNT_TMPFS,
@@ -77,5 +70,3 @@ int mount_custom(const char *dest, CustomMount *mounts, unsigned n, bool userns,
 
 int setup_volatile(const char *directory, VolatileMode mode, bool userns, uid_t uid_shift, uid_t uid_range, const char *selinux_apifs_context);
 int setup_volatile_state(const char *directory, VolatileMode mode, bool userns, uid_t uid_shift, uid_t uid_range, const char *selinux_apifs_context);
-
-VolatileMode volatile_mode_from_string(const char *s);