+sub rename_link_xf ($$$) {
+ # renames/moves or links/copies $src to $dst,
+ # even if $dst is on a different fs
+ # (May use the filename "$dst.tmp".);
+ # On success, returns true.
+ # On failure, returns false and sets
+ # $@ to a reason message
+ # $! to an errno value, or -1 if not known
+ # having possibly printed something about mv to stderr.
+ # Not safe to use without $keeporig if $dst might be a symlink
+ # to $src, as it might delete $src leaving $dst invalid.
+ my ($keeporig,$src,$dst) = @_;
+ if ($keeporig
+ ? link $src, $dst
+ : rename $src, $dst) {
+ return 1;
+ }
+ if ($! != EXDEV) {
+ $@ = "$!";
+ return 0;
+ }
+ if (!stat $src) {
+ $@ = f_ "stat source file: %S", $!;
+ return 0;
+ }
+ my @src_stat = (stat _)[0..1];
+
+ my @dst_stat;
+ if (stat $dst) {
+ @dst_stat = (stat _)[0..1];
+ } elsif ($! == ENOENT) {
+ } else {
+ $@ = f_ "stat destination file: %S", $!;
+ return 0;
+ }
+
+ if ("@src_stat" eq "@dst_stat") {
+ # (Symlinks to) the same file. No need for a copy but
+ # we may need to delete the original.
+ printdebug "rename_link_xf $keeporig $src $dst EXDEV but same\n";
+ } else {
+ $!=0; $?=0;
+ my @cmd = (qw(cp --), $src, "$dst.tmp");
+ debugcmd '+',@cmd;
+ if (system @cmd) {
+ failedcmd_report_cmd undef, @cmd;
+ $@ = failedcmd_waitstatus();
+ $! = -1;
+ return 0;
+ }
+ if (!rename "$dst.tmp", $dst) {
+ $@ = f_ "finally install file after cp: %S", $!;
+ return 0;
+ }
+ }
+ if (!$keeporig) {
+ if (!unlink $src) {
+ $@ = f_ "delete old file after cp: %S", $!;
+ return 0;
+ }
+ }
+ return 1;
+}
+