git-gui/lib/diff.tcl

   1 # git-gui diff viewer
   2 # Copyright (C) 2006, 2007 Shawn Pearce
   3
   4 proc clear_diff {} {
   5         global ui_diff current_diff_path current_diff_header
   6         global ui_index ui_workdir
   7
   8         $ui_diff conf -state normal
   9         $ui_diff delete 0.0 end
  10         $ui_diff conf -state disabled
  11
  12         set current_diff_path {}
  13         set current_diff_header {}
  14
  15         $ui_index tag remove in_diff 0.0 end
  16         $ui_workdir tag remove in_diff 0.0 end
  17 }
  18
  19 proc reshow_diff {{after {}}} {
  20         global file_states file_lists
  21         global current_diff_path current_diff_side
  22         global ui_diff
  23
  24         set p $current_diff_path
  25         if {$p eq {}} {
  26                 # No diff is being shown.
  27         } elseif {$current_diff_side eq {}} {
  28                 clear_diff
  29         } elseif {[catch {set s $file_states($p)}]
  30                 || [lsearch -sorted -exact $file_lists($current_diff_side) $p] == -1} {
  31
  32                 if {[find_next_diff $current_diff_side $p {} {[^O]}]} {
  33                         next_diff $after
  34                 } else {
  35                         clear_diff
  36                 }
  37         } else {
  38                 set save_pos [lindex [$ui_diff yview] 0]
  39                 show_diff $p $current_diff_side {} $save_pos $after
  40         }
  41 }
  42
  43 proc force_diff_encoding {enc} {
  44         global current_diff_path
  45
  46         if {$current_diff_path ne {}} {
  47                 force_path_encoding $current_diff_path $enc
  48                 reshow_diff
  49         }
  50 }
  51
  52 proc handle_empty_diff {} {
  53         global current_diff_path file_states file_lists
  54         global diff_empty_count
  55
  56         set path $current_diff_path
  57         set s $file_states($path)
  58         if {[lindex $s 0] ne {_M} || [has_textconv $path]} return
  59
  60         # Prevent infinite rescan loops
  61         incr diff_empty_count
  62         if {$diff_empty_count > 1} return
  63
  64         info_popup [mc "No differences detected.
  65
  66 %s has no changes.
  67
  68 The modification date of this file was updated by another application, but the content within the file was not changed.
  69
  70 A rescan will be automatically started to find other files which may have the same state." [short_path $path]]
  71
  72         clear_diff
  73         display_file $path __
  74         rescan ui_ready 0
  75 }
  76
  77 proc show_diff {path w {lno {}} {scroll_pos {}} {callback {}}} {
  78         global file_states file_lists
  79         global is_3way_diff is_conflict_diff diff_active repo_config
  80         global ui_diff ui_index ui_workdir
  81         global current_diff_path current_diff_side current_diff_header
  82         global current_diff_queue
  83
  84         if {$diff_active || ![lock_index read]} return
  85
  86         clear_diff
  87         if {$lno == {}} {
  88                 set lno [lsearch -sorted -exact $file_lists($w) $path]
  89                 if {$lno >= 0} {
  90                         incr lno
  91                 }
  92         }
  93         if {$lno >= 1} {
  94                 $w tag add in_diff $lno.0 [expr {$lno + 1}].0
  95                 $w see $lno.0
  96         }
  97
  98         set s $file_states($path)
  99         set m [lindex $s 0]
 100         set is_conflict_diff 0
 101         set current_diff_path $path
 102         set current_diff_side $w
 103         set current_diff_queue {}
 104         ui_status [mc "Loading diff of %s..." [escape_path $path]]
 105
 106         set cont_info [list $scroll_pos $callback]
 107
 108         if {[string first {U} $m] >= 0} {
 109                 merge_load_stages $path [list show_unmerged_diff $cont_info]
 110         } elseif {$m eq {_O}} {
 111                 show_other_diff $path $w $m $cont_info
 112         } else {
 113                 start_show_diff $cont_info
 114         }
 115 }
 116
 117 proc show_unmerged_diff {cont_info} {
 118         global current_diff_path current_diff_side
 119         global merge_stages ui_diff is_conflict_diff
 120         global current_diff_queue
 121
 122         if {$merge_stages(2) eq {}} {
 123                 set is_conflict_diff 1
 124                 lappend current_diff_queue \
 125                         [list [mc "LOCAL: deleted\nREMOTE:\n"] d= \
 126                             [list ":1:$current_diff_path" ":3:$current_diff_path"]]
 127         } elseif {$merge_stages(3) eq {}} {
 128                 set is_conflict_diff 1
 129                 lappend current_diff_queue \
 130                         [list [mc "REMOTE: deleted\nLOCAL:\n"] d= \
 131                             [list ":1:$current_diff_path" ":2:$current_diff_path"]]
 132         } elseif {[lindex $merge_stages(1) 0] eq {120000}
 133                 || [lindex $merge_stages(2) 0] eq {120000}
 134                 || [lindex $merge_stages(3) 0] eq {120000}} {
 135                 set is_conflict_diff 1
 136                 lappend current_diff_queue \
 137                         [list [mc "LOCAL:\n"] d= \
 138                             [list ":1:$current_diff_path" ":2:$current_diff_path"]]
 139                 lappend current_diff_queue \
 140                         [list [mc "REMOTE:\n"] d= \
 141                             [list ":1:$current_diff_path" ":3:$current_diff_path"]]
 142         } else {
 143                 start_show_diff $cont_info
 144                 return
 145         }
 146
 147         advance_diff_queue $cont_info
 148 }
 149
 150 proc advance_diff_queue {cont_info} {
 151         global current_diff_queue ui_diff
 152
 153         set item [lindex $current_diff_queue 0]
 154         set current_diff_queue [lrange $current_diff_queue 1 end]
 155
 156         $ui_diff conf -state normal
 157         $ui_diff insert end [lindex $item 0] [lindex $item 1]
 158         $ui_diff conf -state disabled
 159
 160         start_show_diff $cont_info [lindex $item 2]
 161 }
 162
 163 proc show_other_diff {path w m cont_info} {
 164         global file_states file_lists
 165         global is_3way_diff diff_active repo_config
 166         global ui_diff ui_index ui_workdir
 167         global current_diff_path current_diff_side current_diff_header
 168
 169         # - Git won't give us the diff, there's nothing to compare to!
 170         #
 171         if {$m eq {_O}} {
 172                 set max_sz 100000
 173                 set type unknown
 174                 if {[catch {
 175                                 set type [file type $path]
 176                                 switch -- $type {
 177                                 directory {
 178                                         set type submodule
 179                                         set content {}
 180                                         set sz 0
 181                                 }
 182                                 link {
 183                                         set content [file readlink $path]
 184                                         set sz [string length $content]
 185                                 }
 186                                 file {
 187                                         set fd [open $path r]
 188                                         fconfigure $fd \
 189                                                 -eofchar {} \
 190                                                 -encoding [get_path_encoding $path]
 191                                         set content [read $fd $max_sz]
 192                                         close $fd
 193                                         set sz [file size $path]
 194                                 }
 195                                 default {
 196                                         error "'$type' not supported"
 197                                 }
 198                                 }
 199                         } err ]} {
 200                         set diff_active 0
 201                         unlock_index
 202                         ui_status [mc "Unable to display %s" [escape_path $path]]
 203                         error_popup [strcat [mc "Error loading file:"] "\n\n$err"]
 204                         return
 205                 }
 206                 $ui_diff conf -state normal
 207                 if {$type eq {submodule}} {
 208                         $ui_diff insert end [append \
 209                                 "* " \
 210                                 [mc "Git Repository (subproject)"] \
 211                                 "\n"] d_info
 212                 } elseif {![catch {set type [exec file $path]}]} {
 213                         set n [string length $path]
 214                         if {[string equal -length $n $path $type]} {
 215                                 set type [string range $type $n end]
 216                                 regsub {^:?\s*} $type {} type
 217                         }
 218                         $ui_diff insert end "* $type\n" d_info
 219                 }
 220                 if {[string first "\0" $content] != -1} {
 221                         $ui_diff insert end \
 222                                 [mc "* Binary file (not showing content)."] \
 223                                 d_info
 224                 } else {
 225                         if {$sz > $max_sz} {
 226                                 $ui_diff insert end [mc \
 227 "* Untracked file is %d bytes.
 228 * Showing only first %d bytes.
 229 " $sz $max_sz] d_info
 230                         }
 231                         $ui_diff insert end $content
 232                         if {$sz > $max_sz} {
 233                                 $ui_diff insert end [mc "
 234 * Untracked file clipped here by %s.
 235 * To see the entire file, use an external editor.
 236 " [appname]] d_info
 237                         }
 238                 }
 239                 $ui_diff conf -state disabled
 240                 set diff_active 0
 241                 unlock_index
 242                 set scroll_pos [lindex $cont_info 0]
 243                 if {$scroll_pos ne {}} {
 244                         update
 245                         $ui_diff yview moveto $scroll_pos
 246                 }
 247                 ui_ready
 248                 set callback [lindex $cont_info 1]
 249                 if {$callback ne {}} {
 250                         eval $callback
 251                 }
 252                 return
 253         }
 254 }
 255
 256 proc get_conflict_marker_size {path} {
 257         set size 7
 258         catch {
 259                 set fd_rc [eval [list git_read check-attr "conflict-marker-size" -- $path]]
 260                 set ret [gets $fd_rc line]
 261                 close $fd_rc
 262                 if {$ret > 0} {
 263                         regexp {.*: conflict-marker-size: (\d+)$} $line line size
 264                 }
 265         }
 266         return $size
 267 }
 268
 269 proc start_show_diff {cont_info {add_opts {}}} {
 270         global file_states file_lists
 271         global is_3way_diff is_submodule_diff diff_active repo_config
 272         global ui_diff ui_index ui_workdir
 273         global current_diff_path current_diff_side current_diff_header
 274
 275         set path $current_diff_path
 276         set w $current_diff_side
 277
 278         set s $file_states($path)
 279         set m [lindex $s 0]
 280         set is_3way_diff 0
 281         set is_submodule_diff 0
 282         set diff_active 1
 283         set current_diff_header {}
 284         set conflict_size [get_conflict_marker_size $path]
 285
 286         set cmd [list]
 287         if {$w eq $ui_index} {
 288                 lappend cmd diff-index
 289                 lappend cmd --cached
 290         } elseif {$w eq $ui_workdir} {
 291                 if {[string first {U} $m] >= 0} {
 292                         lappend cmd diff
 293                 } else {
 294                         lappend cmd diff-files
 295                 }
 296         }
 297         if {![is_config_false gui.textconv] && [git-version >= 1.6.1]} {
 298                 lappend cmd --textconv
 299         }
 300
 301         if {[string match {160000 *} [lindex $s 2]]
 302          || [string match {160000 *} [lindex $s 3]]} {
 303                 set is_submodule_diff 1
 304
 305                 if {[git-version >= "1.6.6"]} {
 306                         lappend cmd --submodule
 307                 }
 308         }
 309
 310         lappend cmd -p
 311         lappend cmd --color
 312         if {$repo_config(gui.diffcontext) >= 1} {
 313                 lappend cmd "-U$repo_config(gui.diffcontext)"
 314         }
 315         if {$w eq $ui_index} {
 316                 lappend cmd [PARENT]
 317         }
 318         if {$add_opts ne {}} {
 319                 eval lappend cmd $add_opts
 320         } else {
 321                 lappend cmd --
 322                 lappend cmd $path
 323         }
 324
 325         if {$is_submodule_diff && [git-version < "1.6.6"]} {
 326                 if {$w eq $ui_index} {
 327                         set cmd [list submodule summary --cached -- $path]
 328                 } else {
 329                         set cmd [list submodule summary --files -- $path]
 330                 }
 331         }
 332
 333         if {[catch {set fd [eval git_read --nice $cmd]} err]} {
 334                 set diff_active 0
 335                 unlock_index
 336                 ui_status [mc "Unable to display %s" [escape_path $path]]
 337                 error_popup [strcat [mc "Error loading diff:"] "\n\n$err"]
 338                 return
 339         }
 340
 341         set ::current_diff_inheader 1
 342         fconfigure $fd \
 343                 -blocking 0 \
 344                 -encoding [get_path_encoding $path] \
 345                 -translation lf
 346         fileevent $fd readable [list read_diff $fd $conflict_size $cont_info]
 347 }
 348
 349 proc parse_color_line {line} {
 350         set start 0
 351         set result ""
 352         set markup [list]
 353         set regexp {\033\[((?:\d+;)*\d+)?m}
 354         set need_reset 0
 355         while {[regexp -indices -start $start $regexp $line match code]} {
 356                 foreach {begin end} $match break
 357                 append result [string range $line $start [expr {$begin - 1}]]
 358                 set pos [string length $result]
 359                 set col [eval [linsert $code 0 string range $line]]
 360                 set start [incr end]
 361                 if {$col eq "0" || $col eq ""} {
 362                         if {!$need_reset} continue
 363                         set need_reset 0
 364                 } else {
 365                         set need_reset 1
 366                 }
 367                 lappend markup $pos $col
 368         }
 369         append result [string range $line $start end]
 370         if {[llength $markup] < 4} {set markup {}}
 371         return [list $result $markup]
 372 }
 373
 374 proc read_diff {fd conflict_size cont_info} {
 375         global ui_diff diff_active is_submodule_diff
 376         global is_3way_diff is_conflict_diff current_diff_header
 377         global current_diff_queue
 378         global diff_empty_count
 379
 380         $ui_diff conf -state normal
 381         while {[gets $fd line] >= 0} {
 382                 foreach {line markup} [parse_color_line $line] break
 383                 set line [string map {\033 ^} $line]
 384
 385                 set tags {}
 386
 387                 # -- Check for start of diff header.
 388                 if {   [string match {diff --git *}      $line]
 389                     || [string match {diff --cc *}       $line]
 390                     || [string match {diff --combined *} $line]} {
 391                         set ::current_diff_inheader 1
 392                 }
 393
 394                 # -- Check for end of diff header (any hunk line will do this).
 395                 #
 396                 if {[regexp {^@@+ } $line]} {set ::current_diff_inheader 0}
 397
 398                 # -- Automatically detect if this is a 3 way diff.
 399                 #
 400                 if {[string match {@@@ *} $line]} {set is_3way_diff 1}
 401
 402                 if {$::current_diff_inheader} {
 403
 404                         # -- These two lines stop a diff header and shouldn't be in there
 405                         if {   [string match {Binary files * and * differ} $line]
 406                             || [regexp {^\* Unmerged path }                $line]} {
 407                                 set ::current_diff_inheader 0
 408                         } else {
 409                                 append current_diff_header $line "\n"
 410                         }
 411
 412                         # -- Cleanup uninteresting diff header lines.
 413                         #
 414                         if {   [string match {diff --git *}      $line]
 415                             || [string match {diff --cc *}       $line]
 416                             || [string match {diff --combined *} $line]
 417                             || [string match {--- *}             $line]
 418                             || [string match {+++ *}             $line]
 419                             || [string match {index *}           $line]} {
 420                                 continue
 421                         }
 422
 423                         # -- Name it symlink, not 120000
 424                         #    Note, that the original line is in $current_diff_header
 425                         regsub {^(deleted|new) file mode 120000} $line {\1 symlink} line
 426
 427                 } elseif {   $line eq {\ No newline at end of file}} {
 428                         # -- Handle some special lines
 429                 } elseif {$is_3way_diff} {
 430                         set op [string range $line 0 1]
 431                         switch -- $op {
 432                         {  } {set tags {}}
 433                         {@@} {set tags d_@}
 434                         { +} {set tags d_s+}
 435                         { -} {set tags d_s-}
 436                         {+ } {set tags d_+s}
 437                         {- } {set tags d_-s}
 438                         {--} {set tags d_--}
 439                         {++} {
 440                                 set regexp [string map [list %conflict_size $conflict_size]\
 441                                                                 {^\+\+([<>=]){%conflict_size}(?: |$)}]
 442                                 if {[regexp $regexp $line _g op]} {
 443                                         set is_conflict_diff 1
 444                                         set line [string replace $line 0 1 {  }]
 445                                         set tags d$op
 446                                 } else {
 447                                         set tags d_++
 448                                 }
 449                         }
 450                         default {
 451                                 puts "error: Unhandled 3 way diff marker: {$op}"
 452                                 set tags {}
 453                         }
 454                         }
 455                 } elseif {$is_submodule_diff} {
 456                         if {$line == ""} continue
 457                         if {[regexp {^Submodule } $line]} {
 458                                 set tags d_info
 459                         } elseif {[regexp {^\* } $line]} {
 460                                 set line [string replace $line 0 1 {Submodule }]
 461                                 set tags d_info
 462                         } else {
 463                                 set op [string range $line 0 2]
 464                                 switch -- $op {
 465                                 {  <} {set tags d_-}
 466                                 {  >} {set tags d_+}
 467                                 {  W} {set tags {}}
 468                                 default {
 469                                         puts "error: Unhandled submodule diff marker: {$op}"
 470                                         set tags {}
 471                                 }
 472                                 }
 473                         }
 474                 } else {
 475                         set op [string index $line 0]
 476                         switch -- $op {
 477                         { } {set tags {}}
 478                         {@} {set tags d_@}
 479                         {-} {set tags d_-}
 480                         {+} {
 481                                 set regexp [string map [list %conflict_size $conflict_size]\
 482                                                                 {^\+([<>=]){%conflict_size}(?: |$)}]
 483                                 if {[regexp $regexp $line _g op]} {
 484                                         set is_conflict_diff 1
 485                                         set tags d$op
 486                                 } else {
 487                                         set tags d_+
 488                                 }
 489                         }
 490                         default {
 491                                 puts "error: Unhandled 2 way diff marker: {$op}"
 492                                 set tags {}
 493                         }
 494                         }
 495                 }
 496                 set mark [$ui_diff index "end - 1 line linestart"]
 497                 $ui_diff insert end $line $tags
 498                 if {[string index $line end] eq "\r"} {
 499                         $ui_diff tag add d_cr {end - 2c}
 500                 }
 501                 $ui_diff insert end "\n" $tags
 502
 503                 foreach {posbegin colbegin posend colend} $markup {
 504                         set prefix clr
 505                         foreach style [split $colbegin ";"] {
 506                                 if {$style eq "7"} {append prefix i; continue}
 507                                 if {$style < 30 || $style > 47} {continue}
 508                                 set a "$mark linestart + $posbegin chars"
 509                                 set b "$mark linestart + $posend chars"
 510                                 catch {$ui_diff tag add $prefix$style $a $b}
 511                         }
 512                 }
 513         }
 514         $ui_diff conf -state disabled
 515
 516         if {[eof $fd]} {
 517                 close $fd
 518
 519                 if {$current_diff_queue ne {}} {
 520                         advance_diff_queue $cont_info
 521                         return
 522                 }
 523
 524                 set diff_active 0
 525                 unlock_index
 526                 set scroll_pos [lindex $cont_info 0]
 527                 if {$scroll_pos ne {}} {
 528                         update
 529                         $ui_diff yview moveto $scroll_pos
 530                 }
 531                 ui_ready
 532
 533                 if {[$ui_diff index end] eq {2.0}} {
 534                         handle_empty_diff
 535                 } else {
 536                         set diff_empty_count 0
 537                 }
 538
 539                 set callback [lindex $cont_info 1]
 540                 if {$callback ne {}} {
 541                         eval $callback
 542                 }
 543         }
 544 }
 545
 546 proc apply_hunk {x y} {
 547         global current_diff_path current_diff_header current_diff_side
 548         global ui_diff ui_index file_states
 549
 550         if {$current_diff_path eq {} || $current_diff_header eq {}} return
 551         if {![lock_index apply_hunk]} return
 552
 553         set apply_cmd {apply --cached --whitespace=nowarn}
 554         set mi [lindex $file_states($current_diff_path) 0]
 555         if {$current_diff_side eq $ui_index} {
 556                 set failed_msg [mc "Failed to unstage selected hunk."]
 557                 lappend apply_cmd --reverse
 558                 if {[string index $mi 0] ne {M}} {
 559                         unlock_index
 560                         return
 561                 }
 562         } else {
 563                 set failed_msg [mc "Failed to stage selected hunk."]
 564                 if {[string index $mi 1] ne {M}} {
 565                         unlock_index
 566                         return
 567                 }
 568         }
 569
 570         set s_lno [lindex [split [$ui_diff index @$x,$y] .] 0]
 571         set s_lno [$ui_diff search -backwards -regexp ^@@ $s_lno.0 0.0]
 572         if {$s_lno eq {}} {
 573                 unlock_index
 574                 return
 575         }
 576
 577         set e_lno [$ui_diff search -forwards -regexp ^@@ "$s_lno + 1 lines" end]
 578         if {$e_lno eq {}} {
 579                 set e_lno end
 580         }
 581
 582         if {[catch {
 583                 set enc [get_path_encoding $current_diff_path]
 584                 set p [eval git_write $apply_cmd]
 585                 fconfigure $p -translation binary -encoding $enc
 586                 puts -nonewline $p $current_diff_header
 587                 puts -nonewline $p [$ui_diff get $s_lno $e_lno]
 588                 close $p} err]} {
 589                 error_popup [append $failed_msg "\n\n$err"]
 590                 unlock_index
 591                 return
 592         }
 593
 594         $ui_diff conf -state normal
 595         $ui_diff delete $s_lno $e_lno
 596         $ui_diff conf -state disabled
 597
 598         if {[$ui_diff get 1.0 end] eq "\n"} {
 599                 set o _
 600         } else {
 601                 set o ?
 602         }
 603
 604         if {$current_diff_side eq $ui_index} {
 605                 set mi ${o}M
 606         } elseif {[string index $mi 0] eq {_}} {
 607                 set mi M$o
 608         } else {
 609                 set mi ?$o
 610         }
 611         unlock_index
 612         display_file $current_diff_path $mi
 613         # This should trigger shift to the next changed file
 614         if {$o eq {_}} {
 615                 reshow_diff
 616         }
 617 }
 618
 619 proc apply_range_or_line {x y} {
 620         global current_diff_path current_diff_header current_diff_side
 621         global ui_diff ui_index file_states
 622
 623         set selected [$ui_diff tag nextrange sel 0.0]
 624
 625         if {$selected == {}} {
 626                 set first [$ui_diff index "@$x,$y"]
 627                 set last $first
 628         } else {
 629                 set first [lindex $selected 0]
 630                 set last [lindex $selected 1]
 631         }
 632
 633         set first_l [$ui_diff index "$first linestart"]
 634         set last_l [$ui_diff index "$last lineend"]
 635
 636         if {$current_diff_path eq {} || $current_diff_header eq {}} return
 637         if {![lock_index apply_hunk]} return
 638
 639         set apply_cmd {apply --cached --whitespace=nowarn}
 640         set mi [lindex $file_states($current_diff_path) 0]
 641         if {$current_diff_side eq $ui_index} {
 642                 set failed_msg [mc "Failed to unstage selected line."]
 643                 set to_context {+}
 644                 lappend apply_cmd --reverse
 645                 if {[string index $mi 0] ne {M}} {
 646                         unlock_index
 647                         return
 648                 }
 649         } else {
 650                 set failed_msg [mc "Failed to stage selected line."]
 651                 set to_context {-}
 652                 if {[string index $mi 1] ne {M}} {
 653                         unlock_index
 654                         return
 655                 }
 656         }
 657
 658         set wholepatch {}
 659
 660         while {$first_l < $last_l} {
 661                 set i_l [$ui_diff search -backwards -regexp ^@@ $first_l 0.0]
 662                 if {$i_l eq {}} {
 663                         # If there's not a @@ above, then the selected range
 664                         # must have come before the first_l @@
 665                         set i_l [$ui_diff search -regexp ^@@ $first_l $last_l]
 666                 }
 667                 if {$i_l eq {}} {
 668                         unlock_index
 669                         return
 670                 }
 671                 # $i_l is now at the beginning of a line
 672
 673                 # pick start line number from hunk header
 674                 set hh [$ui_diff get $i_l "$i_l + 1 lines"]
 675                 set hh [lindex [split $hh ,] 0]
 676                 set hln [lindex [split $hh -] 1]
 677
 678                 # There is a special situation to take care of. Consider this
 679                 # hunk:
 680                 #
 681                 #    @@ -10,4 +10,4 @@
 682                 #     context before
 683                 #    -old 1
 684                 #    -old 2
 685                 #    +new 1
 686                 #    +new 2
 687                 #     context after
 688                 #
 689                 # We used to keep the context lines in the order they appear in
 690                 # the hunk. But then it is not possible to correctly stage only
 691                 # "-old 1" and "+new 1" - it would result in this staged text:
 692                 #
 693                 #    context before
 694                 #    old 2
 695                 #    new 1
 696                 #    context after
 697                 #
 698                 # (By symmetry it is not possible to *un*stage "old 2" and "new
 699                 # 2".)
 700                 #
 701                 # We resolve the problem by introducing an asymmetry, namely,
 702                 # when a "+" line is *staged*, it is moved in front of the
 703                 # context lines that are generated from the "-" lines that are
 704                 # immediately before the "+" block. That is, we construct this
 705                 # patch:
 706                 #
 707                 #    @@ -10,4 +10,5 @@
 708                 #     context before
 709                 #    +new 1
 710                 #     old 1
 711                 #     old 2
 712                 #     context after
 713                 #
 714                 # But we do *not* treat "-" lines that are *un*staged in a
 715                 # special way.
 716                 #
 717                 # With this asymmetry it is possible to stage the change "old
 718                 # 1" -> "new 1" directly, and to stage the change "old 2" ->
 719                 # "new 2" by first staging the entire hunk and then unstaging
 720                 # the change "old 1" -> "new 1".
 721                 #
 722                 # Applying multiple lines adds complexity to the special
 723                 # situation.  The pre_context must be moved after the entire
 724                 # first block of consecutive staged "+" lines, so that
 725                 # staging both additions gives the following patch:
 726                 #
 727                 #    @@ -10,4 +10,6 @@
 728                 #     context before
 729                 #    +new 1
 730                 #    +new 2
 731                 #     old 1
 732                 #     old 2
 733                 #     context after
 734
 735                 # This is non-empty if and only if we are _staging_ changes;
 736                 # then it accumulates the consecutive "-" lines (after
 737                 # converting them to context lines) in order to be moved after
 738                 # "+" change lines.
 739                 set pre_context {}
 740
 741                 set n 0
 742                 set m 0
 743                 set i_l [$ui_diff index "$i_l + 1 lines"]
 744                 set patch {}
 745                 while {[$ui_diff compare $i_l < "end - 1 chars"] &&
 746                        [$ui_diff get $i_l "$i_l + 2 chars"] ne {@@}} {
 747                         set next_l [$ui_diff index "$i_l + 1 lines"]
 748                         set c1 [$ui_diff get $i_l]
 749                         if {[$ui_diff compare $first_l <= $i_l] &&
 750                             [$ui_diff compare $i_l < $last_l] &&
 751                             ($c1 eq {-} || $c1 eq {+})} {
 752                                 # a line to stage/unstage
 753                                 set ln [$ui_diff get $i_l $next_l]
 754                                 if {$c1 eq {-}} {
 755                                         set n [expr $n+1]
 756                                         set patch "$patch$pre_context$ln"
 757                                         set pre_context {}
 758                                 } else {
 759                                         set m [expr $m+1]
 760                                         set patch "$patch$ln"
 761                                 }
 762                         } elseif {$c1 ne {-} && $c1 ne {+}} {
 763                                 # context line
 764                                 set ln [$ui_diff get $i_l $next_l]
 765                                 set patch "$patch$pre_context$ln"
 766                                 set n [expr $n+1]
 767                                 set m [expr $m+1]
 768                                 set pre_context {}
 769                         } elseif {$c1 eq $to_context} {
 770                                 # turn change line into context line
 771                                 set ln [$ui_diff get "$i_l + 1 chars" $next_l]
 772                                 if {$c1 eq {-}} {
 773                                         set pre_context "$pre_context $ln"
 774                                 } else {
 775                                         set patch "$patch $ln"
 776                                 }
 777                                 set n [expr $n+1]
 778                                 set m [expr $m+1]
 779                         } else {
 780                                 # a change in the opposite direction of
 781                                 # to_context which is outside the range of
 782                                 # lines to apply.
 783                                 set patch "$patch$pre_context"
 784                                 set pre_context {}
 785                         }
 786                         set i_l $next_l
 787                 }
 788                 set patch "$patch$pre_context"
 789                 set wholepatch "$wholepatch@@ -$hln,$n +$hln,$m @@\n$patch"
 790                 set first_l [$ui_diff index "$next_l + 1 lines"]
 791         }
 792
 793         if {[catch {
 794                 set enc [get_path_encoding $current_diff_path]
 795                 set p [eval git_write $apply_cmd]
 796                 fconfigure $p -translation binary -encoding $enc
 797                 puts -nonewline $p $current_diff_header
 798                 puts -nonewline $p $wholepatch
 799                 close $p} err]} {
 800                 error_popup [append $failed_msg "\n\n$err"]
 801         }
 802
 803         unlock_index
 804 }