summaryrefslogtreecommitdiff
path: root/perl/Git.pm
blob: e9f8c9c048f3e9b7c0e3e492078c1d30a2044d78 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
=head1 NAME

Git - Perl interface to the Git version control system

=cut


package Git;

use strict;


BEGIN {

our ($VERSION, @ISA, @EXPORT, @EXPORT_OK);

# Totally unstable API.
$VERSION = '0.01';


=head1 SYNOPSIS

  use Git;

  my $version = Git::command_oneline('version');

  git_cmd_try { Git::command_noisy('update-server-info') }
              '%s failed w/ code %d';

  my $repo = Git->repository (Directory => '/srv/git/cogito.git');


  my @revs = $repo->command('rev-list', '--since=last monday', '--all');

  my ($fh, $c) = $repo->command_output_pipe('rev-list', '--since=last monday', '--all');
  my $lastrev = <$fh>; chomp $lastrev;
  $repo->command_close_pipe($fh, $c);

  my $lastrev = $repo->command_oneline( [ 'rev-list', '--all' ],
                                        STDERR => 0 );

  my $sha1 = $repo->hash_and_insert_object('file.txt');
  my $tempfile = tempfile();
  my $size = $repo->cat_blob($sha1, $tempfile);

=cut


require Exporter;

@ISA = qw(Exporter);

@EXPORT = qw(git_cmd_try);

# Methods which can be called as standalone functions as well:
@EXPORT_OK = qw(command command_oneline command_noisy
                command_output_pipe command_input_pipe command_close_pipe
                command_bidi_pipe command_close_bidi_pipe
                version exec_path hash_object git_cmd_try
                remote_refs
                temp_acquire temp_release temp_reset temp_path);


=head1 DESCRIPTION

This module provides Perl scripts easy way to interface the Git version control
system. The modules have an easy and well-tested way to call arbitrary Git
commands; in the future, the interface will also provide specialized methods
for doing easily operations which are not totally trivial to do over
the generic command interface.

While some commands can be executed outside of any context (e.g. 'version'
or 'init'), most operations require a repository context, which in practice
means getting an instance of the Git object using the repository() constructor.
(In the future, we will also get a new_repository() constructor.) All commands
called as methods of the object are then executed in the context of the
repository.

Part of the "repository state" is also information about path to the attached
working copy (unless you work with a bare repository). You can also navigate
inside of the working copy using the C<wc_chdir()> method. (Note that
the repository object is self-contained and will not change working directory
of your process.)

TODO: In the future, we might also do

	my $remoterepo = $repo->remote_repository (Name => 'cogito', Branch => 'master');
	$remoterepo ||= Git->remote_repository ('http://git.or.cz/cogito.git/');
	my @refs = $remoterepo->refs();

Currently, the module merely wraps calls to external Git tools. In the future,
it will provide a much faster way to interact with Git by linking directly
to libgit. This should be completely opaque to the user, though (performance
increase notwithstanding).

=cut


use Carp qw(carp croak); # but croak is bad - throw instead
use Error qw(:try);
use Cwd qw(abs_path);
use IPC::Open2 qw(open2);
use Fcntl qw(SEEK_SET SEEK_CUR);
}


=head1 CONSTRUCTORS

=over 4

=item repository ( OPTIONS )

=item repository ( DIRECTORY )

=item repository ()

Construct a new repository object.
C<OPTIONS> are passed in a hash like fashion, using key and value pairs.
Possible options are:

B<Repository> - Path to the Git repository.

B<WorkingCopy> - Path to the associated working copy; not strictly required
as many commands will happily crunch on a bare repository.

B<WorkingSubdir> - Subdirectory in the working copy to work inside.
Just left undefined if you do not want to limit the scope of operations.

B<Directory> - Path to the Git working directory in its usual setup.
The C<.git> directory is searched in the directory and all the parent
directories; if found, C<WorkingCopy> is set to the directory containing
it and C<Repository> to the C<.git> directory itself. If no C<.git>
directory was found, the C<Directory> is assumed to be a bare repository,
C<Repository> is set to point at it and C<WorkingCopy> is left undefined.
If the C<$GIT_DIR> environment variable is set, things behave as expected
as well.

You should not use both C<Directory> and either of C<Repository> and
C<WorkingCopy> - the results of that are undefined.

Alternatively, a directory path may be passed as a single scalar argument
to the constructor; it is equivalent to setting only the C<Directory> option
field.

Calling the constructor with no options whatsoever is equivalent to
calling it with C<< Directory => '.' >>. In general, if you are building
a standard porcelain command, simply doing C<< Git->repository() >> should
do the right thing and setup the object to reflect exactly where the user
is right now.

=cut

sub repository {
	my $class = shift;
	my @args = @_;
	my %opts = ();
	my $self;

	if (defined $args[0]) {
		if ($#args % 2 != 1) {
			# Not a hash.
			$#args == 0 or throw Error::Simple("bad usage");
			%opts = ( Directory => $args[0] );
		} else {
			%opts = @args;
		}
	}

	if (not defined $opts{Repository} and not defined $opts{WorkingCopy}) {
		$opts{Directory} ||= '.';
	}

	if ($opts{Directory}) {
		-d $opts{Directory} or throw Error::Simple("Directory not found: $!");

		my $search = Git->repository(WorkingCopy => $opts{Directory});
		my $dir;
		try {
			$dir = $search->command_oneline(['rev-parse', '--git-dir'],
			                                STDERR => 0);
		} catch Git::Error::Command with {
			$dir = undef;
		};

		if ($dir) {
			$dir =~ m#^/# or $dir = $opts{Directory} . '/' . $dir;
			$opts{Repository} = $dir;

			# If --git-dir went ok, this shouldn't die either.
			my $prefix = $search->command_oneline('rev-parse', '--show-prefix');
			$dir = abs_path($opts{Directory}) . '/';
			if ($prefix) {
				if (substr($dir, -length($prefix)) ne $prefix) {
					throw Error::Simple("rev-parse confused me - $dir does not have trailing $prefix");
				}
				substr($dir, -length($prefix)) = '';
			}
			$opts{WorkingCopy} = $dir;
			$opts{WorkingSubdir} = $prefix;

		} else {
			# A bare repository? Let's see...
			$dir = $opts{Directory};

			unless (-d "$dir/refs" and -d "$dir/objects" and -e "$dir/HEAD") {
				# Mimick git-rev-parse --git-dir error message:
				throw Error::Simple("fatal: Not a git repository: $dir");
			}
			my $search = Git->repository(Repository => $dir);
			try {
				$search->command('symbolic-ref', 'HEAD');
			} catch Git::Error::Command with {
				# Mimick git-rev-parse --git-dir error message:
				throw Error::Simple("fatal: Not a git repository: $dir");
			}

			$opts{Repository} = abs_path($dir);
		}

		delete $opts{Directory};
	}

	$self = { opts => \%opts };
	bless $self, $class;
}

=back

=head1 METHODS

=over 4

=item command ( COMMAND [, ARGUMENTS... ] )

=item command ( [ COMMAND, ARGUMENTS... ], { Opt => Val ... } )

Execute the given Git C<COMMAND> (specify it without the 'git-'
prefix), optionally with the specified extra C<ARGUMENTS>.

The second more elaborate form can be used if you want to further adjust
the command execution. Currently, only one option is supported:

B<STDERR> - How to deal with the command's error output. By default (C<undef>)
it is delivered to the caller's C<STDERR>. A false value (0 or '') will cause
it to be thrown away. If you want to process it, you can get it in a filehandle
you specify, but you must be extremely careful; if the error output is not
very short and you want to read it in the same process as where you called
C<command()>, you are set up for a nice deadlock!

The method can be called without any instance or on a specified Git repository
(in that case the command will be run in the repository context).

In scalar context, it returns all the command output in a single string
(verbatim).

In array context, it returns an array containing lines printed to the
command's stdout (without trailing newlines).

In both cases, the command's stdin and stderr are the same as the caller's.

=cut

sub command {
	my ($fh, $ctx) = command_output_pipe(@_);

	if (not defined wantarray) {
		# Nothing to pepper the possible exception with.
		_cmd_close($fh, $ctx);

	} elsif (not wantarray) {
		local $/;
		my $text = <$fh>;
		try {
			_cmd_close($fh, $ctx);
		} catch Git::Error::Command with {
			# Pepper with the output:
			my $E = shift;
			$E->{'-outputref'} = \$text;
			throw $E;
		};
		return $text;

	} else {
		my @lines = <$fh>;
		defined and chomp for @lines;
		try {
			_cmd_close($fh, $ctx);
		} catch Git::Error::Command with {
			my $E = shift;
			$E->{'-outputref'} = \@lines;
			throw $E;
		};
		return @lines;
	}
}


=item command_oneline ( COMMAND [, ARGUMENTS... ] )

=item command_oneline ( [ COMMAND, ARGUMENTS... ], { Opt => Val ... } )

Execute the given C<COMMAND> in the same way as command()
does but always return a scalar string containing the first line
of the command's standard output.

=cut

sub command_oneline {
	my ($fh, $ctx) = command_output_pipe(@_);

	my $line = <$fh>;
	defined $line and chomp $line;
	try {
		_cmd_close($fh, $ctx);
	} catch Git::Error::Command with {
		# Pepper with the output:
		my $E = shift;
		$E->{'-outputref'} = \$line;
		throw $E;
	};
	return $line;
}


=item command_output_pipe ( COMMAND [, ARGUMENTS... ] )

=item command_output_pipe ( [ COMMAND, ARGUMENTS... ], { Opt => Val ... } )

Execute the given C<COMMAND> in the same way as command()
does but return a pipe filehandle from which the command output can be
read.

The function can return C<($pipe, $ctx)> in array context.
See C<command_close_pipe()> for details.

=cut

sub command_output_pipe {
	_command_common_pipe('-|', @_);
}


=item command_input_pipe ( COMMAND [, ARGUMENTS... ] )

=item command_input_pipe ( [ COMMAND, ARGUMENTS... ], { Opt => Val ... } )

Execute the given C<COMMAND> in the same way as command_output_pipe()
does but return an input pipe filehandle instead; the command output
is not captured.

The function can return C<($pipe, $ctx)> in array context.
See C<command_close_pipe()> for details.

=cut

sub command_input_pipe {
	_command_common_pipe('|-', @_);
}


=item command_close_pipe ( PIPE [, CTX ] )

Close the C<PIPE> as returned from C<command_*_pipe()>, checking
whether the command finished successfully. The optional C<CTX> argument
is required if you want to see the command name in the error message,
and it is the second value returned by C<command_*_pipe()> when
called in array context. The call idiom is:

	my ($fh, $ctx) = $r->command_output_pipe('status');
	while (<$fh>) { ... }
	$r->command_close_pipe($fh, $ctx);

Note that you should not rely on whatever actually is in C<CTX>;
currently it is simply the command name but in future the context might
have more complicated structure.

=cut

sub command_close_pipe {
	my ($self, $fh, $ctx) = _maybe_self(@_);
	$ctx ||= '<unknown>';
	_cmd_close($fh, $ctx);
}

=item command_bidi_pipe ( COMMAND [, ARGUMENTS... ] )

Execute the given C<COMMAND> in the same way as command_output_pipe()
does but return both an input pipe filehandle and an output pipe filehandle.

The function will return return C<($pid, $pipe_in, $pipe_out, $ctx)>.
See C<command_close_bidi_pipe()> for details.

=cut

sub command_bidi_pipe {
	my ($pid, $in, $out);
	$pid = open2($in, $out, 'git', @_);
	return ($pid, $in, $out, join(' ', @_));
}

=item command_close_bidi_pipe ( PID, PIPE_IN, PIPE_OUT [, CTX] )

Close the C<PIPE_IN> and C<PIPE_OUT> as returned from C<command_bidi_pipe()>,
checking whether the command finished successfully. The optional C<CTX>
argument is required if you want to see the command name in the error message,
and it is the fourth value returned by C<command_bidi_pipe()>.  The call idiom
is:

	my ($pid, $in, $out, $ctx) = $r->command_bidi_pipe('cat-file --batch-check');
	print "000000000\n" $out;
	while (<$in>) { ... }
	$r->command_close_bidi_pipe($pid, $in, $out, $ctx);

Note that you should not rely on whatever actually is in C<CTX>;
currently it is simply the command name but in future the context might
have more complicated structure.

=cut

sub command_close_bidi_pipe {
	local $?;
	my ($pid, $in, $out, $ctx) = @_;
	foreach my $fh ($in, $out) {
		unless (close $fh) {
			if ($!) {
				carp "error closing pipe: $!";
			} elsif ($? >> 8) {
				throw Git::Error::Command($ctx, $? >>8);
			}
		}
	}

	waitpid $pid, 0;

	if ($? >> 8) {
		throw Git::Error::Command($ctx, $? >>8);
	}
}


=item command_noisy ( COMMAND [, ARGUMENTS... ] )

Execute the given C<COMMAND> in the same way as command() does but do not
capture the command output - the standard output is not redirected and goes
to the standard output of the caller application.

While the method is called command_noisy(), you might want to as well use
it for the most silent Git commands which you know will never pollute your
stdout but you want to avoid the overhead of the pipe setup when calling them.

The function returns only after the command has finished running.

=cut

sub command_noisy {
	my ($self, $cmd, @args) = _maybe_self(@_);
	_check_valid_cmd($cmd);

	my $pid = fork;
	if (not defined $pid) {
		throw Error::Simple("fork failed: $!");
	} elsif ($pid == 0) {
		_cmd_exec($self, $cmd, @args);
	}
	if (waitpid($pid, 0) > 0 and $?>>8 != 0) {
		throw Git::Error::Command(join(' ', $cmd, @args), $? >> 8);
	}
}


=item version ()

Return the Git version in use.

=cut

sub version {
	my $verstr = command_oneline('--version');
	$verstr =~ s/^git version //;
	$verstr;
}


=item exec_path ()

Return path to the Git sub-command executables (the same as
C<git --exec-path>). Useful mostly only internally.

=cut

sub exec_path { command_oneline('--exec-path') }


=item repo_path ()

Return path to the git repository. Must be called on a repository instance.

=cut

sub repo_path { $_[0]->{opts}->{Repository} }


=item wc_path ()

Return path to the working copy. Must be called on a repository instance.

=cut

sub wc_path { $_[0]->{opts}->{WorkingCopy} }


=item wc_subdir ()

Return path to the subdirectory inside of a working copy. Must be called
on a repository instance.

=cut

sub wc_subdir { $_[0]->{opts}->{WorkingSubdir} ||= '' }


=item wc_chdir ( SUBDIR )

Change the working copy subdirectory to work within. The C<SUBDIR> is
relative to the working copy root directory (not the current subdirectory).
Must be called on a repository instance attached to a working copy
and the directory must exist.

=cut

sub wc_chdir {
	my ($self, $subdir) = @_;
	$self->wc_path()
		or throw Error::Simple("bare repository");

	-d $self->wc_path().'/'.$subdir
		or throw Error::Simple("subdir not found: $!");
	# Of course we will not "hold" the subdirectory so anyone
	# can delete it now and we will never know. But at least we tried.

	$self->{opts}->{WorkingSubdir} = $subdir;
}


=item config ( VARIABLE )

Retrieve the configuration C<VARIABLE> in the same manner as C<config>
does. In scalar context requires the variable to be set only one time
(exception is thrown otherwise), in array context returns allows the
variable to be set multiple times and returns all the values.

This currently wraps command('config') so it is not so fast.

=cut

sub config {
	my ($self, $var) = _maybe_self(@_);

	try {
		my @cmd = ('config');
		unshift @cmd, $self if $self;
		if (wantarray) {
			return command(@cmd, '--get-all', $var);
		} else {
			return command_oneline(@cmd, '--get', $var);
		}
	} catch Git::Error::Command with {
		my $E = shift;
		if ($E->value() == 1) {
			# Key not found.
			return;
		} else {
			throw $E;
		}
	};
}


=item config_bool ( VARIABLE )

Retrieve the bool configuration C<VARIABLE>. The return value
is usable as a boolean in perl (and C<undef> if it's not defined,
of course).

This currently wraps command('config') so it is not so fast.

=cut

sub config_bool {
	my ($self, $var) = _maybe_self(@_);

	try {
		my @cmd = ('config', '--bool', '--get', $var);
		unshift @cmd, $self if $self;
		my $val = command_oneline(@cmd);
		return undef unless defined $val;
		return $val eq 'true';
	} catch Git::Error::Command with {
		my $E = shift;
		if ($E->value() == 1) {
			# Key not found.
			return undef;
		} else {
			throw $E;
		}
	};
}

=item config_int ( VARIABLE )

Retrieve the integer configuration C<VARIABLE>. The return value
is simple decimal number.  An optional value suffix of 'k', 'm',
or 'g' in the config file will cause the value to be multiplied
by 1024, 1048576 (1024^2), or 1073741824 (1024^3) prior to output.
It would return C<undef> if configuration variable is not defined,

This currently wraps command('config') so it is not so fast.

=cut

sub config_int {
	my ($self, $var) = _maybe_self(@_);

	try {
		my @cmd = ('config', '--int', '--get', $var);
		unshift @cmd, $self if $self;
		return command_oneline(@cmd);
	} catch Git::Error::Command with {
		my $E = shift;
		if ($E->value() == 1) {
			# Key not found.
			return undef;
		} else {
			throw $E;
		}
	};
}

=item get_colorbool ( NAME )

Finds if color should be used for NAMEd operation from the configuration,
and returns boolean (true for "use color", false for "do not use color").

=cut

sub get_colorbool {
	my ($self, $var) = @_;
	my $stdout_to_tty = (-t STDOUT) ? "true" : "false";
	my $use_color = $self->command_oneline('config', '--get-colorbool',
					       $var, $stdout_to_tty);
	return ($use_color eq 'true');
}

=item get_color ( SLOT, COLOR )

Finds color for SLOT from the configuration, while defaulting to COLOR,
and returns the ANSI color escape sequence:

	print $repo->get_color("color.interactive.prompt", "underline blue white");
	print "some text";
	print $repo->get_color("", "normal");

=cut

sub get_color {
	my ($self, $slot, $default) = @_;
	my $color = $self->command_oneline('config', '--get-color', $slot, $default);
	if (!defined $color) {
		$color = "";
	}
	return $color;
}

=item remote_refs ( REPOSITORY [, GROUPS [, REFGLOBS ] ] )

This function returns a hashref of refs stored in a given remote repository.
The hash is in the format C<refname =\> hash>. For tags, the C<refname> entry
contains the tag object while a C<refname^{}> entry gives the tagged objects.

C<REPOSITORY> has the same meaning as the appropriate C<git-ls-remote>
argument; either an URL or a remote name (if called on a repository instance).
C<GROUPS> is an optional arrayref that can contain 'tags' to return all the
tags and/or 'heads' to return all the heads. C<REFGLOB> is an optional array
of strings containing a shell-like glob to further limit the refs returned in
the hash; the meaning is again the same as the appropriate C<git-ls-remote>
argument.

This function may or may not be called on a repository instance. In the former
case, remote names as defined in the repository are recognized as repository
specifiers.

=cut

sub remote_refs {
	my ($self, $repo, $groups, $refglobs) = _maybe_self(@_);
	my @args;
	if (ref $groups eq 'ARRAY') {
		foreach (@$groups) {
			if ($_ eq 'heads') {
				push (@args, '--heads');
			} elsif ($_ eq 'tags') {
				push (@args, '--tags');
			} else {
				# Ignore unknown groups for future
				# compatibility
			}
		}
	}
	push (@args, $repo);
	if (ref $refglobs eq 'ARRAY') {
		push (@args, @$refglobs);
	}

	my @self = $self ? ($self) : (); # Ultra trickery
	my ($fh, $ctx) = Git::command_output_pipe(@self, 'ls-remote', @args);
	my %refs;
	while (<$fh>) {
		chomp;
		my ($hash, $ref) = split(/\t/, $_, 2);
		$refs{$ref} = $hash;
	}
	Git::command_close_pipe(@self, $fh, $ctx);
	return \%refs;
}


=item ident ( TYPE | IDENTSTR )

=item ident_person ( TYPE | IDENTSTR | IDENTARRAY )

This suite of functions retrieves and parses ident information, as stored
in the commit and tag objects or produced by C<var GIT_type_IDENT> (thus
C<TYPE> can be either I<author> or I<committer>; case is insignificant).

The C<ident> method retrieves the ident information from C<git var>
and either returns it as a scalar string or as an array with the fields parsed.
Alternatively, it can take a prepared ident string (e.g. from the commit
object) and just parse it.

C<ident_person> returns the person part of the ident - name and email;
it can take the same arguments as C<ident> or the array returned by C<ident>.

The synopsis is like:

	my ($name, $email, $time_tz) = ident('author');
	"$name <$email>" eq ident_person('author');
	"$name <$email>" eq ident_person($name);
	$time_tz =~ /^\d+ [+-]\d{4}$/;

=cut

sub ident {
	my ($self, $type) = _maybe_self(@_);
	my $identstr;
	if (lc $type eq lc 'committer' or lc $type eq lc 'author') {
		my @cmd = ('var', 'GIT_'.uc($type).'_IDENT');
		unshift @cmd, $self if $self;
		$identstr = command_oneline(@cmd);
	} else {
		$identstr = $type;
	}
	if (wantarray) {
		return $identstr =~ /^(.*) <(.*)> (\d+ [+-]\d{4})$/;
	} else {
		return $identstr;
	}
}

sub ident_person {
	my ($self, @ident) = _maybe_self(@_);
	$#ident == 0 and @ident = $self ? $self->ident($ident[0]) : ident($ident[0]);
	return "$ident[0] <$ident[1]>";
}


=item hash_object ( TYPE, FILENAME )

Compute the SHA1 object id of the given C<FILENAME> considering it is
of the C<TYPE> object type (C<blob>, C<commit>, C<tree>).

The method can be called without any instance or on a specified Git repository,
it makes zero difference.

The function returns the SHA1 hash.

=cut

# TODO: Support for passing FILEHANDLE instead of FILENAME
sub hash_object {
	my ($self, $type, $file) = _maybe_self(@_);
	command_oneline('hash-object', '-t', $type, $file);
}


=item hash_and_insert_object ( FILENAME )

Compute the SHA1 object id of the given C<FILENAME> and add the object to the
object database.

The function returns the SHA1 hash.

=cut

# TODO: Support for passing FILEHANDLE instead of FILENAME
sub hash_and_insert_object {
	my ($self, $filename) = @_;

	carp "Bad filename \"$filename\"" if $filename =~ /[\r\n]/;

	$self->_open_hash_and_insert_object_if_needed();
	my ($in, $out) = ($self->{hash_object_in}, $self->{hash_object_out});

	unless (print $out $filename, "\n") {
		$self->_close_hash_and_insert_object();
		throw Error::Simple("out pipe went bad");
	}

	chomp(my $hash = <$in>);
	unless (defined($hash)) {
		$self->_close_hash_and_insert_object();
		throw Error::Simple("in pipe went bad");
	}

	return $hash;
}

sub _open_hash_and_insert_object_if_needed {
	my ($self) = @_;

	return if defined($self->{hash_object_pid});

	($self->{hash_object_pid}, $self->{hash_object_in},
	 $self->{hash_object_out}, $self->{hash_object_ctx}) =
		command_bidi_pipe(qw(hash-object -w --stdin-paths));
}

sub _close_hash_and_insert_object {
	my ($self) = @_;

	return unless defined($self->{hash_object_pid});

	my @vars = map { 'hash_object_' . $_ } qw(pid in out ctx);

	command_close_bidi_pipe(@$self{@vars});
	delete @$self{@vars};
}

=item cat_blob ( SHA1, FILEHANDLE )

Prints the contents of the blob identified by C<SHA1> to C<FILEHANDLE> and
returns the number of bytes printed.

=cut

sub cat_blob {
	my ($self, $sha1, $fh) = @_;

	$self->_open_cat_blob_if_needed();
	my ($in, $out) = ($self->{cat_blob_in}, $self->{cat_blob_out});

	unless (print $out $sha1, "\n") {
		$self->_close_cat_blob();
		throw Error::Simple("out pipe went bad");
	}

	my $description = <$in>;
	if ($description =~ / missing$/) {
		carp "$sha1 doesn't exist in the repository";
		return -1;
	}

	if ($description !~ /^[0-9a-fA-F]{40} \S+ (\d+)$/) {
		carp "Unexpected result returned from git cat-file";
		return -1;
	}

	my $size = $1;

	my $blob;
	my $bytesRead = 0;

	while (1) {
		my $bytesLeft = $size - $bytesRead;
		last unless $bytesLeft;

		my $bytesToRead = $bytesLeft < 1024 ? $bytesLeft : 1024;
		my $read = read($in, $blob, $bytesToRead, $bytesRead);
		unless (defined($read)) {
			$self->_close_cat_blob();
			throw Error::Simple("in pipe went bad");
		}

		$bytesRead += $read;
	}

	# Skip past the trailing newline.
	my $newline;
	my $read = read($in, $newline, 1);
	unless (defined($read)) {
		$self->_close_cat_blob();
		throw Error::Simple("in pipe went bad");
	}
	unless ($read == 1 && $newline eq "\n") {
		$self->_close_cat_blob();
		throw Error::Simple("didn't find newline after blob");
	}

	unless (print $fh $blob) {
		$self->_close_cat_blob();
		throw Error::Simple("couldn't write to passed in filehandle");
	}

	return $size;
}

sub _open_cat_blob_if_needed {
	my ($self) = @_;

	return if defined($self->{cat_blob_pid});

	($self->{cat_blob_pid}, $self->{cat_blob_in},
	 $self->{cat_blob_out}, $self->{cat_blob_ctx}) =
		command_bidi_pipe(qw(cat-file --batch));
}

sub _close_cat_blob {
	my ($self) = @_;

	return unless defined($self->{cat_blob_pid});

	my @vars = map { 'cat_blob_' . $_ } qw(pid in out ctx);

	command_close_bidi_pipe(@$self{@vars});
	delete @$self{@vars};
}


{ # %TEMP_* Lexical Context

my (%TEMP_FILEMAP, %TEMP_FILES);

=item temp_acquire ( NAME )

Attempts to retreive the temporary file mapped to the string C<NAME>. If an
associated temp file has not been created this session or was closed, it is
created, cached, and set for autoflush and binmode.

Internally locks the file mapped to C<NAME>. This lock must be released with
C<temp_release()> when the temp file is no longer needed. Subsequent attempts
to retrieve temporary files mapped to the same C<NAME> while still locked will
cause an error. This locking mechanism provides a weak guarantee and is not
threadsafe. It does provide some error checking to help prevent temp file refs
writing over one another.

In general, the L<File::Handle> returned should not be closed by consumers as
it defeats the purpose of this caching mechanism. If you need to close the temp
file handle, then you should use L<File::Temp> or another temp file faculty
directly. If a handle is closed and then requested again, then a warning will
issue.

=cut

sub temp_acquire {
	my $temp_fd = _temp_cache(@_);

	$TEMP_FILES{$temp_fd}{locked} = 1;
	$temp_fd;
}

=item temp_release ( NAME )

=item temp_release ( FILEHANDLE )

Releases a lock acquired through C<temp_acquire()>. Can be called either with
the C<NAME> mapping used when acquiring the temp file or with the C<FILEHANDLE>
referencing a locked temp file.

Warns if an attempt is made to release a file that is not locked.

The temp file will be truncated before being released. This can help to reduce
disk I/O where the system is smart enough to detect the truncation while data
is in the output buffers. Beware that after the temp file is released and
truncated, any operations on that file may fail miserably until it is
re-acquired. All contents are lost between each release and acquire mapped to
the same string.

=cut

sub temp_release {
	my ($self, $temp_fd, $trunc) = _maybe_self(@_);

	if (exists $TEMP_FILEMAP{$temp_fd}) {
		$temp_fd = $TEMP_FILES{$temp_fd};
	}
	unless ($TEMP_FILES{$temp_fd}{locked}) {
		carp "Attempt to release temp file '",
			$temp_fd, "' that has not been locked";
	}
	temp_reset($temp_fd) if $trunc and $temp_fd->opened;

	$TEMP_FILES{$temp_fd}{locked} = 0;
	undef;
}

sub _temp_cache {
	my ($self, $name) = _maybe_self(@_);

	_verify_require();

	my $temp_fd = \$TEMP_FILEMAP{$name};
	if (defined $$temp_fd and $$temp_fd->opened) {
		if ($TEMP_FILES{$$temp_fd}{locked}) {
			throw Error::Simple("Temp file with moniker '" .
				$name . "' already in use");
		}
	} else {
		if (defined $$temp_fd) {
			# then we're here because of a closed handle.
			carp "Temp file '", $name,
				"' was closed. Opening replacement.";
		}
		my $fname;

		my $tmpdir;
		if (defined $self) {
			$tmpdir = $self->repo_path();
		}

		($$temp_fd, $fname) = File::Temp->tempfile(
			'Git_XXXXXX', UNLINK => 1, DIR => $tmpdir,
			) or throw Error::Simple("couldn't open new temp file");

		$$temp_fd->autoflush;
		binmode $$temp_fd;
		$TEMP_FILES{$$temp_fd}{fname} = $fname;
	}
	$$temp_fd;
}

sub _verify_require {
	eval { require File::Temp; require File::Spec; };
	$@ and throw Error::Simple($@);
}

=item temp_reset ( FILEHANDLE )

Truncates and resets the position of the C<FILEHANDLE>.

=cut

sub temp_reset {
	my ($self, $temp_fd) = _maybe_self(@_);

	truncate $temp_fd, 0
		or throw Error::Simple("couldn't truncate file");
	sysseek($temp_fd, 0, SEEK_SET) and seek($temp_fd, 0, SEEK_SET)
		or throw Error::Simple("couldn't seek to beginning of file");
	sysseek($temp_fd, 0, SEEK_CUR) == 0 and tell($temp_fd) == 0
		or throw Error::Simple("expected file position to be reset");
}

=item temp_path ( NAME )

=item temp_path ( FILEHANDLE )

Returns the filename associated with the given tempfile.

=cut

sub temp_path {
	my ($self, $temp_fd) = _maybe_self(@_);

	if (exists $TEMP_FILEMAP{$temp_fd}) {
		$temp_fd = $TEMP_FILEMAP{$temp_fd};
	}
	$TEMP_FILES{$temp_fd}{fname};
}

sub END {
	unlink values %TEMP_FILEMAP if %TEMP_FILEMAP;
}

} # %TEMP_* Lexical Context

=back

=head1 ERROR HANDLING

All functions are supposed to throw Perl exceptions in case of errors.
See the L<Error> module on how to catch those. Most exceptions are mere
L<Error::Simple> instances.

However, the C<command()>, C<command_oneline()> and C<command_noisy()>
functions suite can throw C<Git::Error::Command> exceptions as well: those are
thrown when the external command returns an error code and contain the error
code as well as access to the captured command's output. The exception class
provides the usual C<stringify> and C<value> (command's exit code) methods and
in addition also a C<cmd_output> method that returns either an array or a
string with the captured command output (depending on the original function
call context; C<command_noisy()> returns C<undef>) and $<cmdline> which
returns the command and its arguments (but without proper quoting).

Note that the C<command_*_pipe()> functions cannot throw this exception since
it has no idea whether the command failed or not. You will only find out
at the time you C<close> the pipe; if you want to have that automated,
use C<command_close_pipe()>, which can throw the exception.

=cut

{
	package Git::Error::Command;

	@Git::Error::Command::ISA = qw(Error);

	sub new {
		my $self = shift;
		my $cmdline = '' . shift;
		my $value = 0 + shift;
		my $outputref = shift;
		my(@args) = ();

		local $Error::Depth = $Error::Depth + 1;

		push(@args, '-cmdline', $cmdline);
		push(@args, '-value', $value);
		push(@args, '-outputref', $outputref);

		$self->SUPER::new(-text => 'command returned error', @args);
	}

	sub stringify {
		my $self = shift;
		my $text = $self->SUPER::stringify;
		$self->cmdline() . ': ' . $text . ': ' . $self->value() . "\n";
	}

	sub cmdline {
		my $self = shift;
		$self->{'-cmdline'};
	}

	sub cmd_output {
		my $self = shift;
		my $ref = $self->{'-outputref'};
		defined $ref or undef;
		if (ref $ref eq 'ARRAY') {
			return @$ref;
		} else { # SCALAR
			return $$ref;
		}
	}
}

=over 4

=item git_cmd_try { CODE } ERRMSG

This magical statement will automatically catch any C<Git::Error::Command>
exceptions thrown by C<CODE> and make your program die with C<ERRMSG>
on its lips; the message will have %s substituted for the command line
and %d for the exit status. This statement is useful mostly for producing
more user-friendly error messages.

In case of no exception caught the statement returns C<CODE>'s return value.

Note that this is the only auto-exported function.

=cut

sub git_cmd_try(&$) {
	my ($code, $errmsg) = @_;
	my @result;
	my $err;
	my $array = wantarray;
	try {
		if ($array) {
			@result = &$code;
		} else {
			$result[0] = &$code;
		}
	} catch Git::Error::Command with {
		my $E = shift;
		$err = $errmsg;
		$err =~ s/\%s/$E->cmdline()/ge;
		$err =~ s/\%d/$E->value()/ge;
		# We can't croak here since Error.pm would mangle
		# that to Error::Simple.
	};
	$err and croak $err;
	return $array ? @result : $result[0];
}


=back

=head1 COPYRIGHT

Copyright 2006 by Petr Baudis E<lt>pasky@suse.czE<gt>.

This module is free software; it may be used, copied, modified
and distributed under the terms of the GNU General Public Licence,
either version 2, or (at your option) any later version.

=cut


# Take raw method argument list and return ($obj, @args) in case
# the method was called upon an instance and (undef, @args) if
# it was called directly.
sub _maybe_self {
	UNIVERSAL::isa($_[0], 'Git') ? @_ : (undef, @_);
}

# Check if the command id is something reasonable.
sub _check_valid_cmd {
	my ($cmd) = @_;
	$cmd =~ /^[a-z0-9A-Z_-]+$/ or throw Error::Simple("bad command: $cmd");
}

# Common backend for the pipe creators.
sub _command_common_pipe {
	my $direction = shift;
	my ($self, @p) = _maybe_self(@_);
	my (%opts, $cmd, @args);
	if (ref $p[0]) {
		($cmd, @args) = @{shift @p};
		%opts = ref $p[0] ? %{$p[0]} : @p;
	} else {
		($cmd, @args) = @p;
	}
	_check_valid_cmd($cmd);

	my $fh;
	if ($^O eq 'MSWin32') {
		# ActiveState Perl
		#defined $opts{STDERR} and
		#	warn 'ignoring STDERR option - running w/ ActiveState';
		$direction eq '-|' or
			die 'input pipe for ActiveState not implemented';
		# the strange construction with *ACPIPE is just to
		# explain the tie below that we want to bind to
		# a handle class, not scalar. It is not known if
		# it is something specific to ActiveState Perl or
		# just a Perl quirk.
		tie (*ACPIPE, 'Git::activestate_pipe', $cmd, @args);
		$fh = *ACPIPE;

	} else {
		my $pid = open($fh, $direction);
		if (not defined $pid) {
			throw Error::Simple("open failed: $!");
		} elsif ($pid == 0) {
			if (defined $opts{STDERR}) {
				close STDERR;
			}
			if ($opts{STDERR}) {
				open (STDERR, '>&', $opts{STDERR})
					or die "dup failed: $!";
			}
			_cmd_exec($self, $cmd, @args);
		}
	}
	return wantarray ? ($fh, join(' ', $cmd, @args)) : $fh;
}

# When already in the subprocess, set up the appropriate state
# for the given repository and execute the git command.
sub _cmd_exec {
	my ($self, @args) = @_;
	if ($self) {
		$self->repo_path() and $ENV{'GIT_DIR'} = $self->repo_path();
		$self->wc_path() and chdir($self->wc_path());
		$self->wc_subdir() and chdir($self->wc_subdir());
	}
	_execv_git_cmd(@args);
	die qq[exec "@args" failed: $!];
}

# Execute the given Git command ($_[0]) with arguments ($_[1..])
# by searching for it at proper places.
sub _execv_git_cmd { exec('git', @_); }

# Close pipe to a subprocess.
sub _cmd_close {
	my ($fh, $ctx) = @_;
	if (not close $fh) {
		if ($!) {
			# It's just close, no point in fatalities
			carp "error closing pipe: $!";
		} elsif ($? >> 8) {
			# The caller should pepper this.
			throw Git::Error::Command($ctx, $? >> 8);
		}
		# else we might e.g. closed a live stream; the command
		# dying of SIGPIPE would drive us here.
	}
}


sub DESTROY {
	my ($self) = @_;
	$self->_close_hash_and_insert_object();
	$self->_close_cat_blob();
}


# Pipe implementation for ActiveState Perl.

package Git::activestate_pipe;
use strict;

sub TIEHANDLE {
	my ($class, @params) = @_;
	# FIXME: This is probably horrible idea and the thing will explode
	# at the moment you give it arguments that require some quoting,
	# but I have no ActiveState clue... --pasky
	# Let's just hope ActiveState Perl does at least the quoting
	# correctly.
	my @data = qx{git @params};
	bless { i => 0, data => \@data }, $class;
}

sub READLINE {
	my $self = shift;
	if ($self->{i} >= scalar @{$self->{data}}) {
		return undef;
	}
	my $i = $self->{i};
	if (wantarray) {
		$self->{i} = $#{$self->{'data'}} + 1;
		return splice(@{$self->{'data'}}, $i);
	}
	$self->{i} = $i + 1;
	return $self->{'data'}->[ $i ];
}

sub CLOSE {
	my $self = shift;
	delete $self->{data};
	delete $self->{i};
}

sub EOF {
	my $self = shift;
	return ($self->{i} >= scalar @{$self->{data}});
}


1; # Famous last words