+sub server_branch ($) { return "$branchprefix/$_[0]"; }
+sub server_ref ($) { return "refs/".server_branch($_[0]); }
+
+sub stat_exists ($) {
+ my ($f) = @_;
+ return 1 if stat $f;
+ return 0 if $!==&ENOENT;
+ die "stat $f: $!";
+}
+
+sub git_for_each_ref ($$) {
+ my ($pattern,$func) = @_;
+ # calls $func->($objid,$objtype,$fullrefname,$reftail);
+ # $reftail is RHS of ref after refs/\w+/
+ # breaks if $pattern matches any ref `refs/blah' where blah has no `/'
+ open GFER, "-|", qw(git for-each-ref), $pattern or die $!;
+ while (<GFER>) {
+ m#^(\w+)\s+(\w+)\s+(refs/\w+/(\S+))\s# or die "$_ ?";
+ $func->($1,$2,$3,$4);
+ }
+ $!=0; $?=0; close GFER or die "$pattern $? $!";
+}
+
+sub git_for_each_tag_referring ($$) {
+ my ($objreferring, $func) = @_;
+ # calls $func->($objid,$fullrefname,$tagname);
+ git_for_each_ref('refs/tags', sub {
+ my ($objid,$objtype,$fullrefname,$tagname) = @_;
+ next unless $objtype eq 'tag';
+ next if defined $objreferring and $objid ne $objreferring;
+ $func->($objid,$fullrefname,$tagname);
+ });
+}
+
+our $debugprefix;
+our $debuglevel = 0;
+
+sub initdebug ($) {
+ ($debugprefix) = @_;
+ open DEBUG, ">/dev/null" or die $!;
+}
+
+sub enabledebug () {
+ open DEBUG, ">&STDERR" or die $!;
+ DEBUG->autoflush(1);
+ $debuglevel ||= 1;
+}
+
+sub enabledebuglevel ($) {
+ my ($newlevel) = @_; # may be undef (eg from env var)
+ die if $debuglevel;
+ $newlevel //= 0;
+ $newlevel += 0;
+ return unless $newlevel;
+ $debuglevel = $newlevel;
+ enabledebug();
+}
+
+sub printdebug {
+ print DEBUG $debugprefix, @_ or die $! if $debuglevel>0;
+}
+
+sub shellquote {
+ my @out;
+ local $_;
+ foreach my $a (@_) {
+ $_ = $a;
+ if (!length || m{[^-=_./0-9a-z]}i) {
+ s{['\\]}{'\\$&'}g;
+ push @out, "'$_'";
+ } else {
+ push @out, $_;
+ }
+ }
+ return join ' ', @out;
+}
+
+sub printcmd {
+ my $fh = shift @_;
+ my $intro = shift @_;
+ print $fh $intro," " or die $!;
+ print $fh shellquote @_ or die $!;
+ print $fh "\n" or die $!;
+}
+
+sub debugcmd {
+ my $extraprefix = shift @_;
+ printcmd(\*DEBUG,$debugprefix.$extraprefix,@_) if $debuglevel>0;
+}
+