summaryrefslogtreecommitdiff
path: root/git-gui/lib/diff.tcl
blob: cf8a95ec346a9a8afa60a3812d59a8caa4bb4c3f (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
# git-gui diff viewer
# Copyright (C) 2006, 2007 Shawn Pearce

proc clear_diff {} {
	global ui_diff current_diff_path current_diff_header
	global ui_index ui_workdir

	$ui_diff conf -state normal
	$ui_diff delete 0.0 end
	$ui_diff conf -state disabled

	set current_diff_path {}
	set current_diff_header {}

	$ui_index tag remove in_diff 0.0 end
	$ui_workdir tag remove in_diff 0.0 end
}

proc reshow_diff {{after {}}} {
	global file_states file_lists
	global current_diff_path current_diff_side
	global ui_diff

	set p $current_diff_path
	if {$p eq {}} {
		# No diff is being shown.
	} elseif {$current_diff_side eq {}} {
		clear_diff
	} elseif {[catch {set s $file_states($p)}]
		|| [lsearch -sorted -exact $file_lists($current_diff_side) $p] == -1} {

		if {[find_next_diff $current_diff_side $p {} {[^O]}]} {
			next_diff $after
		} else {
			clear_diff
		}
	} else {
		set save_pos [lindex [$ui_diff yview] 0]
		show_diff $p $current_diff_side {} $save_pos $after
	}
}

proc force_diff_encoding {enc} {
	global current_diff_path
	
	if {$current_diff_path ne {}} {
		force_path_encoding $current_diff_path $enc
		reshow_diff
	}
}

proc handle_empty_diff {} {
	global current_diff_path file_states file_lists
	global diff_empty_count

	set path $current_diff_path
	set s $file_states($path)
	if {[lindex $s 0] ne {_M} || [has_textconv $path]} return

	# Prevent infinite rescan loops
	incr diff_empty_count
	if {$diff_empty_count > 1} return

	info_popup [mc "No differences detected.

%s has no changes.

The modification date of this file was updated by another application, but the content within the file was not changed.

A rescan will be automatically started to find other files which may have the same state." [short_path $path]]

	clear_diff
	display_file $path __
	rescan ui_ready 0
}

proc show_diff {path w {lno {}} {scroll_pos {}} {callback {}}} {
	global file_states file_lists
	global is_3way_diff is_conflict_diff diff_active repo_config
	global ui_diff ui_index ui_workdir
	global current_diff_path current_diff_side current_diff_header
	global current_diff_queue

	if {$diff_active || ![lock_index read]} return

	clear_diff
	if {$lno == {}} {
		set lno [lsearch -sorted -exact $file_lists($w) $path]
		if {$lno >= 0} {
			incr lno
		}
	}
	if {$lno >= 1} {
		$w tag add in_diff $lno.0 [expr {$lno + 1}].0
		$w see $lno.0
	}

	set s $file_states($path)
	set m [lindex $s 0]
	set is_conflict_diff 0
	set current_diff_path $path
	set current_diff_side $w
	set current_diff_queue {}
	ui_status [mc "Loading diff of %s..." [escape_path $path]]

	set cont_info [list $scroll_pos $callback]

	if {[string first {U} $m] >= 0} {
		merge_load_stages $path [list show_unmerged_diff $cont_info]
	} elseif {$m eq {_O}} {
		show_other_diff $path $w $m $cont_info
	} else {
		start_show_diff $cont_info
	}
}

proc show_unmerged_diff {cont_info} {
	global current_diff_path current_diff_side
	global merge_stages ui_diff is_conflict_diff
	global current_diff_queue

	if {$merge_stages(2) eq {}} {
		set is_conflict_diff 1
		lappend current_diff_queue \
			[list [mc "LOCAL: deleted\nREMOTE:\n"] d= \
			    [list ":1:$current_diff_path" ":3:$current_diff_path"]]
	} elseif {$merge_stages(3) eq {}} {
		set is_conflict_diff 1
		lappend current_diff_queue \
			[list [mc "REMOTE: deleted\nLOCAL:\n"] d= \
			    [list ":1:$current_diff_path" ":2:$current_diff_path"]]
	} elseif {[lindex $merge_stages(1) 0] eq {120000}
		|| [lindex $merge_stages(2) 0] eq {120000}
		|| [lindex $merge_stages(3) 0] eq {120000}} {
		set is_conflict_diff 1
		lappend current_diff_queue \
			[list [mc "LOCAL:\n"] d= \
			    [list ":1:$current_diff_path" ":2:$current_diff_path"]]
		lappend current_diff_queue \
			[list [mc "REMOTE:\n"] d= \
			    [list ":1:$current_diff_path" ":3:$current_diff_path"]]
	} else {
		start_show_diff $cont_info
		return
	}

	advance_diff_queue $cont_info
}

proc advance_diff_queue {cont_info} {
	global current_diff_queue ui_diff

	set item [lindex $current_diff_queue 0]
	set current_diff_queue [lrange $current_diff_queue 1 end]

	$ui_diff conf -state normal
	$ui_diff insert end [lindex $item 0] [lindex $item 1]
	$ui_diff conf -state disabled

	start_show_diff $cont_info [lindex $item 2]
}

proc show_other_diff {path w m cont_info} {
	global file_states file_lists
	global is_3way_diff diff_active repo_config
	global ui_diff ui_index ui_workdir
	global current_diff_path current_diff_side current_diff_header

	# - Git won't give us the diff, there's nothing to compare to!
	#
	if {$m eq {_O}} {
		set max_sz 100000
		set type unknown
		if {[catch {
				set type [file type $path]
				switch -- $type {
				directory {
					set type submodule
					set content {}
					set sz 0
				}
				link {
					set content [file readlink $path]
					set sz [string length $content]
				}
				file {
					set fd [open $path r]
					fconfigure $fd \
						-eofchar {} \
						-encoding [get_path_encoding $path]
					set content [read $fd $max_sz]
					close $fd
					set sz [file size $path]
				}
				default {
					error "'$type' not supported"
				}
				}
			} err ]} {
			set diff_active 0
			unlock_index
			ui_status [mc "Unable to display %s" [escape_path $path]]
			error_popup [strcat [mc "Error loading file:"] "\n\n$err"]
			return
		}
		$ui_diff conf -state normal
		if {$type eq {submodule}} {
			$ui_diff insert end [append \
				"* " \
				[mc "Git Repository (subproject)"] \
				"\n"] d_info
		} elseif {![catch {set type [exec file $path]}]} {
			set n [string length $path]
			if {[string equal -length $n $path $type]} {
				set type [string range $type $n end]
				regsub {^:?\s*} $type {} type
			}
			$ui_diff insert end "* $type\n" d_info
		}
		if {[string first "\0" $content] != -1} {
			$ui_diff insert end \
				[mc "* Binary file (not showing content)."] \
				d_info
		} else {
			if {$sz > $max_sz} {
				$ui_diff insert end [mc \
"* Untracked file is %d bytes.
* Showing only first %d bytes.
" $sz $max_sz] d_info
			}
			$ui_diff insert end $content
			if {$sz > $max_sz} {
				$ui_diff insert end [mc "
* Untracked file clipped here by %s.
* To see the entire file, use an external editor.
" [appname]] d_info
			}
		}
		$ui_diff conf -state disabled
		set diff_active 0
		unlock_index
		set scroll_pos [lindex $cont_info 0]
		if {$scroll_pos ne {}} {
			update
			$ui_diff yview moveto $scroll_pos
		}
		ui_ready
		set callback [lindex $cont_info 1]
		if {$callback ne {}} {
			eval $callback
		}
		return
	}
}

proc get_conflict_marker_size {path} {
	set size 7
	catch {
		set fd_rc [eval [list git_read check-attr "conflict-marker-size" -- $path]]
		set ret [gets $fd_rc line]
		close $fd_rc
		if {$ret > 0} {
			regexp {.*: conflict-marker-size: (\d+)$} $line line size
		}
	}
	return $size
}

proc start_show_diff {cont_info {add_opts {}}} {
	global file_states file_lists
	global is_3way_diff is_submodule_diff diff_active repo_config
	global ui_diff ui_index ui_workdir
	global current_diff_path current_diff_side current_diff_header

	set path $current_diff_path
	set w $current_diff_side

	set s $file_states($path)
	set m [lindex $s 0]
	set is_3way_diff 0
	set is_submodule_diff 0
	set diff_active 1
	set current_diff_header {}
	set conflict_size [get_conflict_marker_size $path]

	set cmd [list]
	if {$w eq $ui_index} {
		lappend cmd diff-index
		lappend cmd --cached
	} elseif {$w eq $ui_workdir} {
		if {[string first {U} $m] >= 0} {
			lappend cmd diff
		} else {
			lappend cmd diff-files
		}
	}
	if {![is_config_false gui.textconv] && [git-version >= 1.6.1]} {
		lappend cmd --textconv
	}

	if {[string match {160000 *} [lindex $s 2]]
	 || [string match {160000 *} [lindex $s 3]]} {
		set is_submodule_diff 1

		if {[git-version >= "1.6.6"]} {
			lappend cmd --submodule
		}
	}

	lappend cmd -p
	lappend cmd --color
	if {$repo_config(gui.diffcontext) >= 1} {
		lappend cmd "-U$repo_config(gui.diffcontext)"
	}
	if {$w eq $ui_index} {
		lappend cmd [PARENT]
	}
	if {$add_opts ne {}} {
		eval lappend cmd $add_opts
	} else {
		lappend cmd --
		lappend cmd $path
	}

	if {$is_submodule_diff && [git-version < "1.6.6"]} {
		if {$w eq $ui_index} {
			set cmd [list submodule summary --cached -- $path]
		} else {
			set cmd [list submodule summary --files -- $path]
		}
	}

	if {[catch {set fd [eval git_read --nice $cmd]} err]} {
		set diff_active 0
		unlock_index
		ui_status [mc "Unable to display %s" [escape_path $path]]
		error_popup [strcat [mc "Error loading diff:"] "\n\n$err"]
		return
	}

	set ::current_diff_inheader 1
	fconfigure $fd \
		-blocking 0 \
		-encoding [get_path_encoding $path] \
		-translation lf
	fileevent $fd readable [list read_diff $fd $conflict_size $cont_info]
}

proc parse_color_line {line} {
	set start 0
	set result ""
	set markup [list]
	set regexp {\033\[((?:\d+;)*\d+)?m}
	set need_reset 0
	while {[regexp -indices -start $start $regexp $line match code]} {
		foreach {begin end} $match break
		append result [string range $line $start [expr {$begin - 1}]]
		set pos [string length $result]
		set col [eval [linsert $code 0 string range $line]]
		set start [incr end]
		if {$col eq "0" || $col eq ""} {
			if {!$need_reset} continue
			set need_reset 0
		} else {
			set need_reset 1
		}
		lappend markup $pos $col
	}
	append result [string range $line $start end]
	if {[llength $markup] < 4} {set markup {}}
	return [list $result $markup]
}

proc read_diff {fd conflict_size cont_info} {
	global ui_diff diff_active is_submodule_diff
	global is_3way_diff is_conflict_diff current_diff_header
	global current_diff_queue
	global diff_empty_count

	$ui_diff conf -state normal
	while {[gets $fd line] >= 0} {
		foreach {line markup} [parse_color_line $line] break
		set line [string map {\033 ^} $line]

		set tags {}

		# -- Check for start of diff header.
		if {   [string match {diff --git *}      $line]
		    || [string match {diff --cc *}       $line]
		    || [string match {diff --combined *} $line]} {
			set ::current_diff_inheader 1
		}

		# -- Check for end of diff header (any hunk line will do this).
		#
		if {[regexp {^@@+ } $line]} {set ::current_diff_inheader 0}

		# -- Automatically detect if this is a 3 way diff.
		#
		if {[string match {@@@ *} $line]} {set is_3way_diff 1}

		if {$::current_diff_inheader} {

			# -- These two lines stop a diff header and shouldn't be in there
			if {   [string match {Binary files * and * differ} $line]
			    || [regexp {^\* Unmerged path }                $line]} {
				set ::current_diff_inheader 0
			} else {
				append current_diff_header $line "\n"
			}

			# -- Cleanup uninteresting diff header lines.
			#
			if {   [string match {diff --git *}      $line]
			    || [string match {diff --cc *}       $line]
			    || [string match {diff --combined *} $line]
			    || [string match {--- *}             $line]
			    || [string match {+++ *}             $line]
			    || [string match {index *}           $line]} {
				continue
			}

			# -- Name it symlink, not 120000
			#    Note, that the original line is in $current_diff_header
			regsub {^(deleted|new) file mode 120000} $line {\1 symlink} line

		} elseif {   $line eq {\ No newline at end of file}} {
			# -- Handle some special lines
		} elseif {$is_3way_diff} {
			set op [string range $line 0 1]
			switch -- $op {
			{  } {set tags {}}
			{@@} {set tags d_@}
			{ +} {set tags d_s+}
			{ -} {set tags d_s-}
			{+ } {set tags d_+s}
			{- } {set tags d_-s}
			{--} {set tags d_--}
			{++} {
				set regexp [string map [list %conflict_size $conflict_size]\
								{^\+\+([<>=]){%conflict_size}(?: |$)}]
				if {[regexp $regexp $line _g op]} {
					set is_conflict_diff 1
					set line [string replace $line 0 1 {  }]
					set tags d$op
				} else {
					set tags d_++
				}
			}
			default {
				puts "error: Unhandled 3 way diff marker: {$op}"
				set tags {}
			}
			}
		} elseif {$is_submodule_diff} {
			if {$line == ""} continue
			if {[regexp {^Submodule } $line]} {
				set tags d_info
			} elseif {[regexp {^\* } $line]} {
				set line [string replace $line 0 1 {Submodule }]
				set tags d_info
			} else {
				set op [string range $line 0 2]
				switch -- $op {
				{  <} {set tags d_-}
				{  >} {set tags d_+}
				{  W} {set tags {}}
				default {
					puts "error: Unhandled submodule diff marker: {$op}"
					set tags {}
				}
				}
			}
		} else {
			set op [string index $line 0]
			switch -- $op {
			{ } {set tags {}}
			{@} {set tags d_@}
			{-} {set tags d_-}
			{+} {
				set regexp [string map [list %conflict_size $conflict_size]\
								{^\+([<>=]){%conflict_size}(?: |$)}]
				if {[regexp $regexp $line _g op]} {
					set is_conflict_diff 1
					set tags d$op
				} else {
					set tags d_+
				}
			}
			default {
				puts "error: Unhandled 2 way diff marker: {$op}"
				set tags {}
			}
			}
		}
		set mark [$ui_diff index "end - 1 line linestart"]
		$ui_diff insert end $line $tags
		if {[string index $line end] eq "\r"} {
			$ui_diff tag add d_cr {end - 2c}
		}
		$ui_diff insert end "\n" $tags

		foreach {posbegin colbegin posend colend} $markup {
			set prefix clr
			foreach style [split $colbegin ";"] {
				if {$style eq "7"} {append prefix i; continue}
				if {$style < 30 || $style > 47} {continue}
				set a "$mark linestart + $posbegin chars"
				set b "$mark linestart + $posend chars"
				catch {$ui_diff tag add $prefix$style $a $b}
			}
		}
	}
	$ui_diff conf -state disabled

	if {[eof $fd]} {
		close $fd

		if {$current_diff_queue ne {}} {
			advance_diff_queue $cont_info
			return
		}

		set diff_active 0
		unlock_index
		set scroll_pos [lindex $cont_info 0]
		if {$scroll_pos ne {}} {
			update
			$ui_diff yview moveto $scroll_pos
		}
		ui_ready

		if {[$ui_diff index end] eq {2.0}} {
			handle_empty_diff
		} else {
			set diff_empty_count 0
		}

		set callback [lindex $cont_info 1]
		if {$callback ne {}} {
			eval $callback
		}
	}
}

proc apply_hunk {x y} {
	global current_diff_path current_diff_header current_diff_side
	global ui_diff ui_index file_states

	if {$current_diff_path eq {} || $current_diff_header eq {}} return
	if {![lock_index apply_hunk]} return

	set apply_cmd {apply --cached --whitespace=nowarn}
	set mi [lindex $file_states($current_diff_path) 0]
	if {$current_diff_side eq $ui_index} {
		set failed_msg [mc "Failed to unstage selected hunk."]
		lappend apply_cmd --reverse
		if {[string index $mi 0] ne {M}} {
			unlock_index
			return
		}
	} else {
		set failed_msg [mc "Failed to stage selected hunk."]
		if {[string index $mi 1] ne {M}} {
			unlock_index
			return
		}
	}

	set s_lno [lindex [split [$ui_diff index @$x,$y] .] 0]
	set s_lno [$ui_diff search -backwards -regexp ^@@ $s_lno.0 0.0]
	if {$s_lno eq {}} {
		unlock_index
		return
	}

	set e_lno [$ui_diff search -forwards -regexp ^@@ "$s_lno + 1 lines" end]
	if {$e_lno eq {}} {
		set e_lno end
	}

	if {[catch {
		set enc [get_path_encoding $current_diff_path]
		set p [eval git_write $apply_cmd]
		fconfigure $p -translation binary -encoding $enc
		puts -nonewline $p $current_diff_header
		puts -nonewline $p [$ui_diff get $s_lno $e_lno]
		close $p} err]} {
		error_popup [append $failed_msg "\n\n$err"]
		unlock_index
		return
	}

	$ui_diff conf -state normal
	$ui_diff delete $s_lno $e_lno
	$ui_diff conf -state disabled

	if {[$ui_diff get 1.0 end] eq "\n"} {
		set o _
	} else {
		set o ?
	}

	if {$current_diff_side eq $ui_index} {
		set mi ${o}M
	} elseif {[string index $mi 0] eq {_}} {
		set mi M$o
	} else {
		set mi ?$o
	}
	unlock_index
	display_file $current_diff_path $mi
	# This should trigger shift to the next changed file
	if {$o eq {_}} {
		reshow_diff
	}
}

proc apply_range_or_line {x y} {
	global current_diff_path current_diff_header current_diff_side
	global ui_diff ui_index file_states

	set selected [$ui_diff tag nextrange sel 0.0]

	if {$selected == {}} {
		set first [$ui_diff index "@$x,$y"]
		set last $first
	} else {
		set first [lindex $selected 0]
		set last [lindex $selected 1]
	}

	set first_l [$ui_diff index "$first linestart"]
	set last_l [$ui_diff index "$last lineend"]

	if {$current_diff_path eq {} || $current_diff_header eq {}} return
	if {![lock_index apply_hunk]} return

	set apply_cmd {apply --cached --whitespace=nowarn}
	set mi [lindex $file_states($current_diff_path) 0]
	if {$current_diff_side eq $ui_index} {
		set failed_msg [mc "Failed to unstage selected line."]
		set to_context {+}
		lappend apply_cmd --reverse
		if {[string index $mi 0] ne {M}} {
			unlock_index
			return
		}
	} else {
		set failed_msg [mc "Failed to stage selected line."]
		set to_context {-}
		if {[string index $mi 1] ne {M}} {
			unlock_index
			return
		}
	}

	set wholepatch {}

	while {$first_l < $last_l} {
		set i_l [$ui_diff search -backwards -regexp ^@@ $first_l 0.0]
		if {$i_l eq {}} {
			# If there's not a @@ above, then the selected range
			# must have come before the first_l @@
			set i_l [$ui_diff search -regexp ^@@ $first_l $last_l]
		}
		if {$i_l eq {}} {
			unlock_index
			return
		}
		# $i_l is now at the beginning of a line

		# pick start line number from hunk header
		set hh [$ui_diff get $i_l "$i_l + 1 lines"]
		set hh [lindex [split $hh ,] 0]
		set hln [lindex [split $hh -] 1]

		# There is a special situation to take care of. Consider this
		# hunk:
		#
		#    @@ -10,4 +10,4 @@
		#     context before
		#    -old 1
		#    -old 2
		#    +new 1
		#    +new 2
		#     context after
		#
		# We used to keep the context lines in the order they appear in
		# the hunk. But then it is not possible to correctly stage only
		# "-old 1" and "+new 1" - it would result in this staged text:
		#
		#    context before
		#    old 2
		#    new 1
		#    context after
		#
		# (By symmetry it is not possible to *un*stage "old 2" and "new
		# 2".)
		#
		# We resolve the problem by introducing an asymmetry, namely,
		# when a "+" line is *staged*, it is moved in front of the
		# context lines that are generated from the "-" lines that are
		# immediately before the "+" block. That is, we construct this
		# patch:
		#
		#    @@ -10,4 +10,5 @@
		#     context before
		#    +new 1
		#     old 1
		#     old 2
		#     context after
		#
		# But we do *not* treat "-" lines that are *un*staged in a
		# special way.
		#
		# With this asymmetry it is possible to stage the change "old
		# 1" -> "new 1" directly, and to stage the change "old 2" ->
		# "new 2" by first staging the entire hunk and then unstaging
		# the change "old 1" -> "new 1".
		#
		# Applying multiple lines adds complexity to the special
		# situation.  The pre_context must be moved after the entire
		# first block of consecutive staged "+" lines, so that
		# staging both additions gives the following patch:
		#
		#    @@ -10,4 +10,6 @@
		#     context before
		#    +new 1
		#    +new 2
		#     old 1
		#     old 2
		#     context after

		# This is non-empty if and only if we are _staging_ changes;
		# then it accumulates the consecutive "-" lines (after
		# converting them to context lines) in order to be moved after
		# "+" change lines.
		set pre_context {}

		set n 0
		set m 0
		set i_l [$ui_diff index "$i_l + 1 lines"]
		set patch {}
		while {[$ui_diff compare $i_l < "end - 1 chars"] &&
		       [$ui_diff get $i_l "$i_l + 2 chars"] ne {@@}} {
			set next_l [$ui_diff index "$i_l + 1 lines"]
			set c1 [$ui_diff get $i_l]
			if {[$ui_diff compare $first_l <= $i_l] &&
			    [$ui_diff compare $i_l < $last_l] &&
			    ($c1 eq {-} || $c1 eq {+})} {
				# a line to stage/unstage
				set ln [$ui_diff get $i_l $next_l]
				if {$c1 eq {-}} {
					set n [expr $n+1]
					set patch "$patch$pre_context$ln"
					set pre_context {}
				} else {
					set m [expr $m+1]
					set patch "$patch$ln"
				}
			} elseif {$c1 ne {-} && $c1 ne {+}} {
				# context line
				set ln [$ui_diff get $i_l $next_l]
				set patch "$patch$pre_context$ln"
				set n [expr $n+1]
				set m [expr $m+1]
				set pre_context {}
			} elseif {$c1 eq $to_context} {
				# turn change line into context line
				set ln [$ui_diff get "$i_l + 1 chars" $next_l]
				if {$c1 eq {-}} {
					set pre_context "$pre_context $ln"
				} else {
					set patch "$patch $ln"
				}
				set n [expr $n+1]
				set m [expr $m+1]
			} else {
				# a change in the opposite direction of
				# to_context which is outside the range of
				# lines to apply.
				set patch "$patch$pre_context"
				set pre_context {}
			}
			set i_l $next_l
		}
		set patch "$patch$pre_context"
		set wholepatch "$wholepatch@@ -$hln,$n +$hln,$m @@\n$patch"
		set first_l [$ui_diff index "$next_l + 1 lines"]
	}

	if {[catch {
		set enc [get_path_encoding $current_diff_path]
		set p [eval git_write $apply_cmd]
		fconfigure $p -translation binary -encoding $enc
		puts -nonewline $p $current_diff_header
		puts -nonewline $p $wholepatch
		close $p} err]} {
		error_popup [append $failed_msg "\n\n$err"]
	}

	unlock_index
}