strv: declare iterator of FOREACH_STRING() in the loop

Same idea as 03677889f0.

No functional change intended. The type of the iterator is generally changed to
be 'const char*' instead of 'char*'. Despite the type commonly used, modifying
the string was not allowed.

I adjusted the naming of some short variables for clarity and reduced the scope
of some variable declarations in code that was being touched anyway.

src/nspawn/nspawn-cgroup.c

@@ -22,7 +22,6 @@
 
 static int chown_cgroup_path(const char *path, uid_t uid_shift) {
         _cleanup_close_ int fd = -1;
-        const char *fn;
 
         fd = open(path, O_RDONLY|O_CLOEXEC|O_DIRECTORY);
         if (fd < 0)

src/nspawn/nspawn-mount.c

@@ -404,7 +404,7 @@ int tmpfs_patch_options(
 }
 
 int mount_sysfs(const char *dest, MountSettingsMask mount_settings) {
-        const char *full, *top, *x;
+        const char *full, *top;
         int r;
         unsigned long extra_flags = 0;
 
@@ -464,7 +464,7 @@ int mount_sysfs(const char *dest, MountSettingsMask mount_settings) {
         /* Create mountpoint for cgroups. Otherwise we are not allowed since we
          * remount /sys read-only.
          */
-        x = prefix_roota(top, "/fs/cgroup");
+        const char *x = prefix_roota(top, "/fs/cgroup");
         (void) mkdir_p(x, 0755);
 
         return mount_nofollow_verbose(LOG_ERR, NULL, top, NULL,

src/nspawn/nspawn.c

@@ -2564,7 +2564,7 @@ static int setup_hostname(void) {
 
 static int setup_journal(const char *directory) {
         _cleanup_free_ char *d = NULL;
-        const char *dirname, *p, *q;
+        const char *p, *q;
         sd_id128_t this_id;
         bool try;
         int r;
@@ -3512,7 +3512,6 @@ static int inner_child(
         (void) fdset_close_others(fds);
 
         if (arg_start_mode == START_BOOT) {
-                const char *init;
                 char **a;
                 size_t m;
 
@@ -4603,7 +4602,7 @@ static int load_settings(void) {
         _cleanup_(settings_freep) Settings *settings = NULL;
         _cleanup_fclose_ FILE *f = NULL;
         _cleanup_free_ char *p = NULL;
-        const char *fn, *i;
+        const char *fn;
         int r;
 
         if (arg_oci_bundle)