#!/usr/bin/perl -w

# Compare the documentation of different OTP versions
# and detect missing or incorrect "since" attributes.
#
# The script checks out the supplied git tags one at time and reads
# all xml files searching for documented modules and their functions.
#
# The script is not perfect. For example some function docs use an old
# ambiguous way of declaring default arguments, like foo(Arg1 [,Arg2]).

#use strict;
use File::Basename;
 
my $progname = basename($0);
#my $tagfile = shift @ARGV;
my $skip_branches = 0;
my $verbose = 0;
my $single_module;
my $read_stdin = 1;
my @tag_list;

while (@ARGV >= 1 and $ARGV[0] =~ /^-/) {   
    if ($ARGV[0] eq "-s") {
	$skip_branches = 1;
    }
    elsif ($ARGV[0] eq "-v") {
	$verbose = 1;
    }
    elsif ($ARGV[0] eq "-m" && @ARGV >= 2) {
	$single_module = $ARGV[1];
	shift @ARGV;
    }
    elsif ($ARGV[0] eq "-t" && @ARGV >= 3) {
	@tag_list = ($ARGV[1], $ARGV[2]);
	shift @ARGV;
	shift @ARGV;
	$read_stdin = 0;
    }
    else {
	die "Syntax: $progname [-h] [-s] [-v] [-m <module>] [-t <new-tag> <old-tag>]\n" .
	    "-s\tSkip unordered tags\n" .
	    "-h\tThis help\n" .
	    "-v\tVerbose\n" .
	    "-m <module>\tAnalyze only one module\n" .
	    "-t <new-tag> <old-tag>\tTags to compare\n\n" .
	    "Without -t reads git tags from STDIN, one per line, sorted from newest to oldest\n";
    }
    shift @ARGV;
}
 
0 == @ARGV or die "Too many arguments\n";
 
my %facc; # Function accumulator
my %mods; # Modules
my %mods_since; # Since attribute seen for modules
 
my %skip_files = (
    'lib/kernel/doc/src/packages.xml' => 1
    );
 
# foo([Bar])
# 1: foo has arities 1 and 0 (one optional argument Bar).
# 0: foo has one argument (a list of Bar's).
my %ambiguous_0args = (
    'io:columns' => 1,
    'io:nl' => 1,
    'io:getopts' => 1,
    'io:rows' => 1,
    'eldap:open' => 0,
    "eldap:'and'" => 0,
    "eldap:'or'" => 0,
    'net_kernel:start' => 0,
    'fprof:trace' => 0,
    'fprof:profile' => 0,
    'fprof:analyse' => 0,
    'lcnt:conflicts' => 0,
    'lcnt:locations' => 0,
    'tags:root' => 1,
    'ts:cross_cover_analyse' => 0,
    'gen_sctp:open' => 0,
    'c:memory' => 0,
    'supervisor:check_childspecs' => 0

    );
 
# List of arities.
my %complex_arglist = (
    'mnesia:sync_transaction' => [1,2,3],
    'mnesia:table' => [1,2],
    'mnesia:transaction' => [1,2,3],
    'mnesia:traverse_backup' => [4,6],
    'public_key:pem_entry_encode' => [2,3],
    'qlc:string_to_handle' => [1,2,3],
    'ttb:tp' => [2,3,4],
    'ttb:tpl' => [2,3,4],
    'ttb:ctp' => [1,2,3],
    'ttb:ctpl' => [1,2,3],
    'ttb:ctpg' => [1,2,3]
    );

my %suppressions = (
    'beam_lib:strip/2' => 'OTP 22.0',
    'beam_lib:strip_files/2' => 'OTP 22.0',
    'beam_lib:strip_release/2' => 'OTP 22.0',
    'crypto:crypto_final/1' => 'OTP 23.0',
    'crypto:crypto_get_data/1' => 'OTP 23.0',
    'ct_property_test:present_result/4' => 'OTP 22.3',
    'ct_property_test:present_result/5' => 'OTP 22.3',
    'dialyzer:format_warning/2' => 'R14B02',
    'ei_global:ei_global_names/C' => 'OTP 23.0',
    'ei_global:ei_global_register/C' => 'OTP 23.0',
    'ei_global:ei_global_unregister/C' => 'OTP 23.0',
    'ei_global:ei_global_whereis/C' => 'OTP 23.0',
    'eprof:profile/4' => "",
    'public_key:pkix_hash_type/1' => 'OTP 23.0',
    'public_key:pkix_subject_id/1' => 'OTP 23.1',
    'snmpa:which_transports/0' => 'OTP 23.3',
    'snmpm:restart/1' => 'OTP 22.3',
    'ssh:connection_info/1' => 'OTP 22.1',
    'ssh:daemon_info/2' => 'OTP 22.1',
    'ssh:get_sock_opts/2' => 'OTP 22.3',
    'ssh:set_sock_opts/2' => 'OTP 22.3',
    'ssh:tcpip_tunnel_from_server/5' => 'OTP 23.0',
    'ssh:tcpip_tunnel_from_server/6' => 'OTP 23.0',
    'ssh:tcpip_tunnel_to_server/5' => 'OTP 23.0',
    'ssh:tcpip_tunnel_to_server/6' => 'OTP 23.0',
    'ssh_agent:add_host_key/3' => 'OTP 23.0',
    'ssh_agent:add_host_key/4' => 'OTP 23.0',
    'ssh_agent:is_host_key/4' => 'OTP 23.0',
    'ssh_agent:is_host_key/5' => 'OTP 23.0',
    'ssh_agent:user_key/2' => 'OTP 23.0',
    );


my %seen_shas;
my %warnings;
local $tag;
my $prev_tag;
 
 
#
# First checkout top tag and find all documented modules and functions
# that might have been first introduced in one of the following tags.
#
local $/ = "\n";
if (next_tag(\$tag)) {
 
    if ($skip_branches) {
                          $tag =~ /^(OTP-\d+\.\d+(\.\d+)?)|(OTP_R\d+B(0\d)?(-\d)?)$/
                              or die "First tag must be usable\n";
    }

    if ($verbose) {
	print STDERR "Check out $tag\n";
    }
    my $output = qx(git checkout -f $tag 2>&1);
    $? == 0 or fatal("'git checkout -f $tag failed:\n $output");
 
    my $xml_files;
    if ($single_module) {
	$xml_files = qx(git ls-files '*/$single_module.xml' 2>&1);
	$? == 0 or fatal("'git ls-files '*.xml' failed:\n $xml_files");
    }
    else {
	$xml_files = qx(git ls-files '*.xml' 2>&1);
	$? == 0 or fatal("'git ls-files '*.xml' failed:\n $xml_files");
    }
 
    while ($xml_files =~ m/\n*([^\n]+)/g) {
	local $filename = $1;
	
	#if (seen_it()) {
	#    next;
	#}
	
	my $module;
	my $module_since;
	my %funcs = read_xml_functions($tag, \$module, \$module_since);
	
	if (keys %funcs) {
	    if (!$module) {
		die "No <module> tag in $filename\n";
	    }
	    if (exists($mods{$module})) {
		die "Duplicate module $mods{$module} and $filename\n";
	    }
	    $mods{$module} = $filename;
	    $mods_since{$module} = $module_since;
	    
	    foreach my $f (keys %funcs) {
		!exists($facc{$f})
		    or die "Duplicate function $f???\n";
		$facc{$f} = $funcs{$f};
	    }
	}
	elsif ($single_module) {
	    die "File $filename has no functions\n";
	}
    }
}
else {
    die "No tags read on STDIN\n";
}
 
#
# Now go through the older tags in reverse time order
# and detect when documented modules or functions "disappear",
# in which case they must have been introduced in the previous
# inspected tag.
#
$prev_tag = $tag;
while (next_tag(\$tag)) {
 
    if ($skip_branches) {
	if ($tag !~ /^((OTP-\d+\.\d+(\.\d+)?)|(OTP_R\d+B(0\d)?(-\d)?))$/) {
	    print STDERR "Skip tag $tag\n";
	    next;
	}
	#print STDERR "Keep tag $tag 1='$1' 2='$2' 3='$3' 4='$4' 5='$5'\n";
    }

    if ($verbose) {
	print STDERR "Check out $tag\n";
    }
    my $output = qx(git checkout -f $tag 2>&1);
    $? == 0 or fatal("'git checkout -f $tag failed:\n $output");
 
    my $xml_files;
    if ($single_module) {
	$xml_files = qx(git ls-files '*/$single_module.xml' 2>&1);
	$? == 0 or fatal("'git ls-files '*.xml' failed:\n $xml_files");
    }
    else {
	$xml_files = qx(git ls-files '*.xml' 2>&1);
	$? == 0 or fatal("'git ls-files '*.xml' failed:\n $xml_files");
    }
 
    my %prev_facc = %facc;
    %facc = ();
    my %prev_mods = %mods;
    %mods = ();
 
    while ($xml_files =~ m/\n*([^\n]+)/g) {
	local $filename = $1;
	
	#if (seen_it()) {
	#    next;
	#}
	
	my $module;
	my $module_since;
	my %funcs = read_xml_functions($tag, \$module, \$module_since);
	
	if (keys %funcs) {
	    if (!$module) {
		die "No <module> tag in $filename\n";
	    }
	    if (exists($mods{$module})) {
		die "Duplicate module in $mods{$module} and $filename\n";
	    }
	    
	    if (exists($prev_mods{$module})) {
		foreach my $f (keys %funcs) {
		    if (exists($prev_facc{$f})) {
			$facc{$f} = $funcs{$f};
			#print "prev_facc{$f} = $prev_facc{$f}\n";
			#print "prev_facc{$f} = @{$prev_facc{$f}}\n";
			if (delete_versions(\@{$facc{$f}}, \@{$prev_facc{$f}})) {
			    delete $prev_facc{$f};
			}
		    }
		    else {
			#print "Ignoring removed function $f\n";
		    }
		}
		$mods{$module} = $filename;
		delete $prev_mods{$module};
	    }
	    else {
		#print "Ignoring removed module $module\n";
	    }
	}
	elsif ($single_module) {
	    die "File $filename has no functions\n";
	}
    }
    
    my $erl_file;
    foreach my $mod (keys %prev_mods) {
	if ($single_module and $single_module ne $mod) {
	    next;
	}
	$erl_file = qx(git ls-files '*/src*/$mod.erl' 2>&1);
	$? == 0 or fatal("'git ls-files '$mod.erl' failed:\n $erl_file");
	if ($erl_file) {
	    local $filename = trim($erl_file);
	    my %funcs = read_edoc_functions($tag, $mod);
	    if (keys %funcs) {
		foreach my $f (keys %funcs) {
		    if (exists($prev_facc{$f})) {
			$facc{$f} = $funcs{$f}[0];
			delete $prev_facc{$f};
		    }
		}
		$mods{$mod} = $filename;
		delete $prev_mods{$mod};
	    }
	    else {
		#warning("No \@spec functions in $filename\n");
	    }
	}
    }
    if ($single_module and !$xml_files and !$erl_file) {
	warning("No $single_module.xml or .erl found\n");
    }
    
    my $headline = "\nTAG: $prev_tag\n";
    
    foreach my $mod (sort keys %prev_mods) {
	print "${headline}MODULE: $mod since=$mods_since{$mod}\n";
	$headline = "";
    }
    foreach my $f (sort keys %prev_facc) {
	filter_newer_versions($tag, \@{$prev_facc{$f}});
	if (@{$prev_facc{$f}} != 0) {
            if (@{$prev_facc{$f}} != 1 ||
                !exists($suppressions{$f}) ||
                $suppressions{$f} ne $prev_facc{$f}->[0])
            {
                print "${headline}FUNC: $f since = @{$prev_facc{$f}}\n";
                $headline = "";
            }
	}
    }
    $prev_tag = $tag;
}
 
#close TAGFILE;

if ($verbose) {
    #
    # Print all stoneage modules and functions, that "always" existed.
    #
    my $headline = "\nTAG:\n";
    foreach my $mod (sort keys %mods) {
	print "${headline}MODULE: $mod\n";
	$headline = "";
    }
    foreach my $f (sort keys %facc) {
	print "${headline}FUNC: $f\n";
	$headline = "";
    }
}

# Delete all versions from second array that exists in first array.
# Return true if no versions left in second array.
sub delete_versions {
    my ($olds_ref, $news_ref) = @_;

    #print "olds_ref = $olds_ref\n";
    #print "news_ref = $news_ref\n";
    #print "olds = @{$olds_ref}\n";
    #print "news = @{$news_ref}\n";

    foreach my $old (@{$olds_ref}) {
	#print "old = $old\n";
	for (my $i = 0; $i < @{$news_ref}; $i++) {
	    if (($old eq $news_ref->[$i])
		or (fixver($old) eq $news_ref->[$i])) {
		#print "$i: remove $news_ref->[$i]\n";
		splice @{$news_ref}, $i, 1;
		last;
	    }
	    #print "$i: keep $news_ref->[$i]\n";
	}
    }

    # Do a sloppy attempt to detect missing since tags that has
    # been corrected in new version.
    # For all with "missing" since tag in old, remove one version from new.
    foreach my $old (@{$olds_ref}) {           
	if (@$news_ref == 0) {
	    last;
	}
	if ($old eq "missing") {
	    #print "Remove fixed missing version $news_ref->[0]\n";
	    shift @{$news_ref};
	}
    }   
    
    my $ret = (@$news_ref == 0);
    #print "ret = $ret\n";
    return $ret;
}


# Try correct misspelled OTP version
sub fixver {
    my ($otp_ver) = @_;

    if ($otp_ver =~ /^OTP \d\d\.\d/) {
	# Looks ok
	return $otp_ver;
    }

    # Try correct any combination of:
    # missing OTP
    # - instead of space
    # missing .0
    if ($otp_ver =~ /^(OTP)?[ -](\d\d)(\.(.+))?/) {
	my $major = $2;
	my $minor = $3 ? $4 : "0";
	my $fixed = "OTP $major.$minor";
	#print "fixver $otp_ver -> $fixed\n";
	return $fixed;
    }
    return $otp_ver;
}

# Remove all versions newer than $ver from @$ver_list_ref
sub filter_newer_versions {
    my ($ver, $ver_list_ref) = @_;

    $ver = fixver($ver);

    for (my $i = 0; $i < @{$ver_list_ref}; ) {
	if ($ver le fixver($ver_list_ref->[$i])) {
	    #print "$i: filter $ver_list_ref->[$i]\n";
	    splice @{$ver_list_ref}, $i, 1;
	}
	else {
	    #print "$i: keep $ver_list_ref->[$i]\n";
	    $i++;
	}
    }
}

sub read_xml_functions {
    my($tag, $module_ref, $module_since_ref) = @_;

    if ($verbose) {
	print "XML-file: $filename\n";
    }

    open(FILE, $filename) or die "Cant open xml file \"$filename\"\n";
    local $/ = undef;
    my $lines = <FILE>;
    close(FILE);
 
    my %functions;
 
    if (exists($skip_files{$filename})) {
	return %functions; # empty
    }

    # Is this a <module> or <lib> reference doc file?
    if ($lines =~ /<module(\s*since=\"([^"]*)\")?>([\w]+)<\/module>/) {
	if ($1) {
	    $$module_since_ref = $2;
	}
	else {
	    $$module_since_ref = "missing";
	}
	$$module_ref = $3;
    }
    elsif ($lines =~ /<lib>([\w]+)<\/lib>/) {
	$$module_ref = $1;
	$$module_since_ref = "lib";
    }
    else {
	#print "XML-file <module> or <lib> not found\n";
	return %functions; # empty
    }
 
    while ($lines =~ /<func>\s*/g) {
	my $func_cnt = 0;
	
	# Find all <name> within <func> (usually only one but may be more, ex io:format,fwrite)
	while (1) {
	    my @farity;
	    my $fname;
	    
	    $lines =~ /(<name|<\/func>)/g
		or die "<func> without </func> in $filename\n";
	    
	    if ($1 eq '</func>') {
		last;
	    }
	    
	    $func_cnt++;
	    
	    # C-lib
	    # <name since=""><ret>..</ret><nametext>c_function(..)</nametext></name>
	    if ($lines =~ /\G(\s*since=\"([^"]*)\")?>\s*<ret>.*?<\/ret>\s*<nametext>\*?(\w+)[^<]*?<\/nametext>\s*<\/name>/sgc) {
		$fname = $3;
		my $since;
		if ($1) {
		    $since = $2;
		}
		else {
		    $since = "missing";
		}
		push @farity, { arity => 'C', since => $since };
	    }
	    # Old style: <name>... </name>
	    # or (rare) <name name="foo">... </name>
	    elsif ($lines =~ /\G(\s*name=\"(\w+)\")?(\s*since=\"([^"]*)\")?>/gc) {
		if ($1) {
		    $fname = $2;
		}
		my $since;
		if ($3) {
		    $since = $4;
		}
		else {
		    $since = "missing";
		}
		
		# <name>foo(Arg1,Arg2)
		# <name>erlang:foo(Arg1,Arg2)
		# <name>'Foo'(Arg1,Arg2)
		# <name>Module:callback(Arg1,Arg2)
		# The cryptic arglist part of the regex below search for end ')'
		# while ignoring '()' that might exists for argument types like 'integer()'.
		if ($lines =~ /\G\s*((\w+):)?('?\w+'?)\s*\((([^()]*(\(\))?)*)\)/gc) {
		    my $module = $2;
		    if ($fname) {
			$fname eq $3
			    or die "Conflicting function names '$fname' vs '$3' in $filename\n";
		    }
		    else {
			$fname = $3;
		    }
		    my $arglist = $4;
		    if ($module) {
			if ($module =~ /^[A-Z]/) {
			    $module = $$module_ref;
			    $fname = "Callback#$fname";
			}
			elsif ($module ne $$module_ref) {
			    die "Strange module prefix '$module' of function '$fname' in $filename\n";
			}
		    }
		    @farity = count_args($arglist, $fname, $$module_ref, $since);
		}
		elsif ($lines =~ /\G(.*)/gc) {
		    warning("Strange function prototype '$1' in file $filename\n");
		    next;
		}
		else {
		    die "WTF in $filename\n";
		}
	    }
	    # New style?:
	    # <name name="foo" arity="2"/>
	    # <name name="foo" arity="2"></name>
	    elsif ($lines =~ /(([^\/]*\/)*?[^\/]*)(\/>|>\s*<\/name>)/gc) {
		my $name_body = $1;
		$name_body =~ m/name=\"\'?(\w+)\'?\"/
		    or die "$filename: No function name in \'$name_body\'\n";
		$fname = $1;
		
		$name_body =~ m/arity=\"(\d+)\"/
		    or die "$filename: No function arity in \'$name_body\'\n";
		my $arity = $1;

		my $since;
		if ($name_body =~ m/since=\"([^"]*)\"/) {
		    $since = $1;
		    #print "$$module_ref:$fname/$arity since = $since\n";
		}
		else {
		    $since = "missing";
		}

		push @farity, { arity => $arity, since => $since };
	    }
	    elsif ($lines =~ /(\G.*)/g) {
		warning("Strange name tag '<name$1' in file $filename\n");
		next;
	    }
	    else {
		die "Very strange <name> tag in $filename\n";
	    }
	    

	    #print "$$module_ref:$fname in $filename\n";
	    foreach my $fa_since (@farity) {
		#while (($key, $value) = each (%$fa_since)) {
		#    print "$key => $value\n";
		#}
		my $fa = $$fa_since{arity};
		my $since = $$fa_since{since};
		#print "$$module_ref:$fname/$fa since=$since\n";
		push @{ $functions{"$$module_ref:$fname/$fa"} }, $since;
	    }
	}
	if ($func_cnt < 1) {
	    die "<func> without <name> in $filename\n";
	}
	
    }
    
    return %functions;
}

sub read_edoc_functions {
    my($tag, $module) = @_;
    
    open(FILE, $filename) or die "Can't open erl file \"$filename\"\n";
    local $/ = undef;
    my $lines = <FILE>;
    close(FILE);
 
    my %functions;
 
    if (exists($skip_files{$filename})) {
	return %functions; # empty
    }
    if ($lines !~ /^\s*-module\(([\w]+)\)\./m) {
	die "No -module() found in erl file \"$filename\"\n";
    }
    if ($1 ne $module) {
	die "Mismatching module name '$1' != '$module' in erl file \"$filename\"\n";
    }
 
    # % @spec foo(Arg1,Arg2)
    # -spec foo(Arg1,Arg2)
    while ($lines =~ /\n\s*(%.*\@spec|-spec\s*)/g) {
	if ($lines !~ /(\w*)\s*\(/g) {
	    warning("Strange \@spec function name in $filename");
	}
	my $fname = $1;
	
	if ($fname eq '') {
	    my $save_pos = pos($lines);
	    if ($lines !~ /\n\s*(\w+)\s*\(/g) {
		warning("No function found after anonymous \@spec in $filename");
	    }
	    $fname = $1;
	    pos($lines) = $save_pos;
	}
	
	if ($lines !~ /\G(([^()]*(\(\))?)*)\)/gc) {
	    if ($lines =~ /(\G.*)/g) {
		warning("Strange \@spec argument list '$1' for '$fname' in file $filename\n");
		next;
	    }
	    else {
		die "WTF \@spec for '$fname' in $filename\n";
	    }
	}
	my $arglist = $1;
	my @arities = count_args($arglist, $fname, $module, "edoc");
	
	foreach my $fa_since (@arities) {
	    my $fa = $$fa_since{arity};
	    push @{ $functions{"$module:$fname/$fa"} }, $tag;

	    #print "Found edoc function '$module:$fname/$fa'\n";
	}
    }
    
    return %functions;
}

sub count_args {
    my($arglist,$fname,$module,$since) = @_;
    my @arities;
 
    #print "count_args $module:$fname($arglist)\n";
 
    $arglist = trim($arglist);
    if ($arglist eq '') {
	#print "Empty arg list for $fname\n";
	push @arities, { arity => 0, since => $since};
	return @arities;
    }
    
    if ($arglist =~ /^\s*\[\s*\w+\s*\]\s*$/gc) {
	#
	# Oh dear! Is "[Foo]" a list of Foo's or an optional Foo????
	#
	if (exists($ambiguous_0args{"$module:$fname"})) {
	    if ($ambiguous_0args{"$module:$fname"}) {
		push @arities, { arity => 0, since => $since};
	    }
	}
	else {
	    warning("Ambigiuous arglist $module:$fname($arglist) in $filename\n");
	}

	push @arities, { arity => 1, since => $since};
	return @arities;
    }
    
    # Starts with [Arg,] ?
    my $first_optional = 0;
    if ($arglist =~ /^\[\s*\w+\s*,\s*\]/gc) {
	$first_optional = 1;
    }
 
    # Ends with [,Arg] ?
    my $last_optional = 0;
    if ($arglist =~ /(.+)\[\s*,\s*\w+\s*\]$/gc) {
	$last_optional = 1;
	$arglist = $1;
    }
 
    # Give up if any other "[," or ",]" left?
    if ($arglist =~ /(\[\s*,)|(,\s*\])/gc) {
	if (!exists($complex_arglist{"$module:$fname"})) {
	    warning("Complex optional arguments for $module:$fname($arglist)\n");
	}
	foreach my $fa (@{$complex_arglist{"$module:$fname"}}) {
	    #print "complex_arglist: $module:$fname/$fa\n";
	    push @arities, { arity => $fa, since => $since };
	}
	return @arities;
    }
 
    my $nargs = 0;
    my $expect_comma = 'no';
    
    while ($arglist =~ /([\w,[{])/g) {
	if ($1 eq ',') {
	    $expect_comma ne 'no'
		or die "$filename: Unexpected comma in arglist '$arglist' for '$fname'\n";
	    $expect_comma = 'no';
	}
	elsif ($1 eq '[' or $1 eq '{') {
	    $expect_comma ne 'yes'
		or die "$filename: Missing comma in arglist '$arglist' for '$fname'\n";
	    
	    my $paren = $1;
	    skip_term(\$arglist, $paren, 1);
	    $nargs++;
	    $expect_comma = 'yes';
	}
	else {
	    $expect_comma ne 'yes'
		or die "$filename: Expected comma but found arg in '$arglist' for '$fname'\n";
	    if ($expect_comma eq 'no') {
		$nargs++;
	    }
	    $expect_comma = 'maybe';
	}
    }
    push @arities, { arity => $nargs, since => $since};
    if ($first_optional) {
	$nargs = $nargs + 1;
	push @arities, { arity => $nargs, since => $since};
    }
    if ($last_optional) {
	$nargs = $nargs + 1;
	push @arities, { arity => $nargs, since => $since};
    }

    #foreach my $h (@arities) {
    #    print "count_args: $module:$fname/$$h{arity}\n";
    #}
 
    return @arities;
}
 
sub skip_term {
    my($arglist_ref,$paren,$recurs) = @_;
    
    #my $pp = pos($$arglist_ref);
    #print "skip_term($$arglist_ref,$paren) pos=$pp\n";
 
    $recurs < 10 or fatal("$filename: Evil recursion\n");
 
    while (1) {
	my $recurs_paren;
	if ($paren eq '[') {
	    if ($$arglist_ref !~ /([][{])/g) {
		my $pp = pos($$arglist_ref);
		die "$filename: No matching ']' in '$$arglist_ref' at pos=$pp\n";
	    }
	    if ($1 eq ']') {
		last;
	    }
	    $recurs_paren = $1;
	}
	elsif ($paren eq '{') {
	    $$arglist_ref =~ /([}[{])/g
			       or die "$filename: No matching '}' in '$$arglist_ref'\n";
	    if ($1 eq '}') {
		last;
	    }
	    $recurs_paren = $1;
	}
	else {
	    die "$filename: WTF? in arglist '$$arglist_ref'\n";
	}
	skip_term($arglist_ref, $recurs_paren, $recurs+1);
    }
    #$pp = pos($$arglist_ref);
    #print "skip_term($$arglist_ref,$paren) returns pos=$pp\n";
}
 
sub seen_it {
    my $sha = qx(git rev-parse :$filename 2>&1);
    $? == 0 or fatal("'git rev-parse :$filename failed:\n $sha");
    if (exists($seen_shas{$sha})) {
	return 1;
    }
    $seen_shas{$sha} = 1;
    return 0;
}
 
 
# Trim leading and trailing whitespace
sub trim {
    my $s = shift;
    $s =~ s/^\s+|\s+$//g;
    return $s;
}
 
sub warning {
    my $str = shift;
    if (exists($warnings{$str})) {
	return;
    }
    $warnings{$str} = 1;
 
    print STDERR "WARNING: $tag $str";
}
 
sub fatal {
    select()->flush();
    die "$progname: @_\n";
}

sub next_tag {
    my $tag_ref = shift;

    if ($read_stdin) {
	my $line = <STDIN>;
	if ($line) {
	    $$tag_ref = trim($line);
	    return 1;
	}
    }
    elsif (@tag_list > 0) {
	$$tag_ref = shift @tag_list;
	return 1;
    }
    return 0;
}