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 $s 0] ne {_M}} return
  59
  60         # Prevent infinite rescan loops
  61         incr diff_empty_count
  62         if {$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_@
 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_@
 219                 }
 220                 if {[string first "\0" $content] != -1} {
 221                         $ui_diff insert end \
 222                                 [mc "* Binary file (not showing content)."] \
 223                                 d_@
 224                 } else {
 225                         if {$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_@
 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_@
 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 start_show_diff {cont_info {add_opts {}}} {
 257         global file_states file_lists
 258         global is_3way_diff is_submodule_diff diff_active repo_config
 259         global ui_diff ui_index ui_workdir
 260         global current_diff_path current_diff_side current_diff_header
 261
 262         set path $current_diff_path
 263         set w $current_diff_side
 264
 265         set s $file_states($path)
 266         set m [lindex $s 0]
 267         set is_3way_diff 0
 268         set is_submodule_diff 0
 269         set diff_active 1
 270         set current_diff_header {}
 271
 272         set cmd [list]
 273         if {$w eq $ui_index} {
 274                 lappend cmd diff-index
 275                 lappend cmd --cached
 276         } elseif {$w eq $ui_workdir} {
 277                 if {[string first {U} $m] >= 0} {
 278                         lappend cmd diff
 279                 } else {
 280                         lappend cmd diff-files
 281                 }
 282         }
 283
 284         if {[string match {160000 *} [lindex $s 2]]
 285          || [string match {160000 *} [lindex $s 3]]} {
 286                 set is_submodule_diff 1
 287
 288                 if {[git-version >= "1.6.6"]} {
 289                         lappend cmd --submodule
 290                 }
 291         }
 292
 293         lappend cmd -p
 294         lappend cmd --no-color
 295         if {$repo_config(gui.diffcontext) >= 1} {
 296                 lappend cmd "-U$repo_config(gui.diffcontext)"
 297         }
 298         if {$w eq $ui_index} {
 299                 lappend cmd [PARENT]
 300         }
 301         if {$add_opts ne {}} {
 302                 eval lappend cmd $add_opts
 303         } else {
 304                 lappend cmd --
 305                 lappend cmd $path
 306         }
 307
 308         if {$is_submodule_diff && [git-version < "1.6.6"]} {
 309                 if {$w eq $ui_index} {
 310                         set cmd [list submodule summary --cached -- $path]
 311                 } else {
 312                         set cmd [list submodule summary --files -- $path]
 313                 }
 314         }
 315
 316         if {[catch {set fd [eval git_read --nice $cmd]} err]} {
 317                 set diff_active 0
 318                 unlock_index
 319                 ui_status [mc "Unable to display %s" [escape_path $path]]
 320                 error_popup [strcat [mc "Error loading diff:"] "\n\n$err"]
 321                 return
 322         }
 323
 324         set ::current_diff_inheader 1
 325         fconfigure $fd \
 326                 -blocking 0 \
 327                 -encoding [get_path_encoding $path] \
 328                 -translation lf
 329         fileevent $fd readable [list read_diff $fd $cont_info]
 330 }
 331
 332 proc read_diff {fd cont_info} {
 333         global ui_diff diff_active is_submodule_diff
 334         global is_3way_diff is_conflict_diff current_diff_header
 335         global current_diff_queue
 336         global diff_empty_count
 337
 338         $ui_diff conf -state normal
 339         while {[gets $fd line] >= 0} {
 340                 # -- Cleanup uninteresting diff header lines.
 341                 #
 342                 if {$::current_diff_inheader} {
 343                         if {   [string match {diff --git *}      $line]
 344                             || [string match {diff --cc *}       $line]
 345                             || [string match {diff --combined *} $line]
 346                             || [string match {--- *}             $line]
 347                             || [string match {+++ *}             $line]} {
 348                                 append current_diff_header $line "\n"
 349                                 continue
 350                         }
 351                 }
 352                 if {[string match {index *} $line]} continue
 353                 if {$line eq {deleted file mode 120000}} {
 354                         set line "deleted symlink"
 355                 }
 356                 set ::current_diff_inheader 0
 357
 358                 # -- Automatically detect if this is a 3 way diff.
 359                 #
 360                 if {[string match {@@@ *} $line]} {set is_3way_diff 1}
 361
 362                 if {[string match {mode *} $line]
 363                         || [string match {new file *} $line]
 364                         || [regexp {^(old|new) mode *} $line]
 365                         || [string match {deleted file *} $line]
 366                         || [string match {deleted symlink} $line]
 367                         || [string match {Binary files * and * differ} $line]
 368                         || $line eq {\ No newline at end of file}
 369                         || [regexp {^\* Unmerged path } $line]} {
 370                         set tags {}
 371                 } elseif {$is_3way_diff} {
 372                         set op [string range $line 0 1]
 373                         switch -- $op {
 374                         {  } {set tags {}}
 375                         {@@} {set tags d_@}
 376                         { +} {set tags d_s+}
 377                         { -} {set tags d_s-}
 378                         {+ } {set tags d_+s}
 379                         {- } {set tags d_-s}
 380                         {--} {set tags d_--}
 381                         {++} {
 382                                 if {[regexp {^\+\+([<>]{7} |={7})} $line _g op]} {
 383                                         set is_conflict_diff 1
 384                                         set line [string replace $line 0 1 {  }]
 385                                         set tags d$op
 386                                 } else {
 387                                         set tags d_++
 388                                 }
 389                         }
 390                         default {
 391                                 puts "error: Unhandled 3 way diff marker: {$op}"
 392                                 set tags {}
 393                         }
 394                         }
 395                 } elseif {$is_submodule_diff} {
 396                         if {$line == ""} continue
 397                         if {[regexp {^Submodule } $line]} {
 398                                 set tags d_@
 399                         } elseif {[regexp {^\* } $line]} {
 400                                 set line [string replace $line 0 1 {Submodule }]
 401                                 set tags d_@
 402                         } else {
 403                                 set op [string range $line 0 2]
 404                                 switch -- $op {
 405                                 {  <} {set tags d_-}
 406                                 {  >} {set tags d_+}
 407                                 {  W} {set tags {}}
 408                                 default {
 409                                         puts "error: Unhandled submodule diff marker: {$op}"
 410                                         set tags {}
 411                                 }
 412                                 }
 413                         }
 414                 } else {
 415                         set op [string index $line 0]
 416                         switch -- $op {
 417                         { } {set tags {}}
 418                         {@} {set tags d_@}
 419                         {-} {set tags d_-}
 420                         {+} {
 421                                 if {[regexp {^\+([<>]{7} |={7})} $line _g op]} {
 422                                         set is_conflict_diff 1
 423                                         set tags d$op
 424                                 } else {
 425                                         set tags d_+
 426                                 }
 427                         }
 428                         default {
 429                                 puts "error: Unhandled 2 way diff marker: {$op}"
 430                                 set tags {}
 431                         }
 432                         }
 433                 }
 434                 $ui_diff insert end $line $tags
 435                 if {[string index $line end] eq "\r"} {
 436                         $ui_diff tag add d_cr {end - 2c}
 437                 }
 438                 $ui_diff insert end "\n" $tags
 439         }
 440         $ui_diff conf -state disabled
 441
 442         if {[eof $fd]} {
 443                 close $fd
 444
 445                 if {$current_diff_queue ne {}} {
 446                         advance_diff_queue $cont_info
 447                         return
 448                 }
 449
 450                 set diff_active 0
 451                 unlock_index
 452                 set scroll_pos [lindex $cont_info 0]
 453                 if {$scroll_pos ne {}} {
 454                         update
 455                         $ui_diff yview moveto $scroll_pos
 456                 }
 457                 ui_ready
 458
 459                 if {[$ui_diff index end] eq {2.0}} {
 460                         handle_empty_diff
 461                 } else {
 462                         set diff_empty_count 0
 463                 }
 464
 465                 set callback [lindex $cont_info 1]
 466                 if {$callback ne {}} {
 467                         eval $callback
 468                 }
 469         }
 470 }
 471
 472 proc apply_hunk {x y} {
 473         global current_diff_path current_diff_header current_diff_side
 474         global ui_diff ui_index file_states
 475
 476         if {$current_diff_path eq {} || $current_diff_header eq {}} return
 477         if {![lock_index apply_hunk]} return
 478
 479         set apply_cmd {apply --cached --whitespace=nowarn}
 480         set mi [lindex $file_states($current_diff_path) 0]
 481         if {$current_diff_side eq $ui_index} {
 482                 set failed_msg [mc "Failed to unstage selected hunk."]
 483                 lappend apply_cmd --reverse
 484                 if {[string index $mi 0] ne {M}} {
 485                         unlock_index
 486                         return
 487                 }
 488         } else {
 489                 set failed_msg [mc "Failed to stage selected hunk."]
 490                 if {[string index $mi 1] ne {M}} {
 491                         unlock_index
 492                         return
 493                 }
 494         }
 495
 496         set s_lno [lindex [split [$ui_diff index @$x,$y] .] 0]
 497         set s_lno [$ui_diff search -backwards -regexp ^@@ $s_lno.0 0.0]
 498         if {$s_lno eq {}} {
 499                 unlock_index
 500                 return
 501         }
 502
 503         set e_lno [$ui_diff search -forwards -regexp ^@@ "$s_lno + 1 lines" end]
 504         if {$e_lno eq {}} {
 505                 set e_lno end
 506         }
 507
 508         if {[catch {
 509                 set enc [get_path_encoding $current_diff_path]
 510                 set p [eval git_write $apply_cmd]
 511                 fconfigure $p -translation binary -encoding $enc
 512                 puts -nonewline $p $current_diff_header
 513                 puts -nonewline $p [$ui_diff get $s_lno $e_lno]
 514                 close $p} err]} {
 515                 error_popup [append $failed_msg "\n\n$err"]
 516                 unlock_index
 517                 return
 518         }
 519
 520         $ui_diff conf -state normal
 521         $ui_diff delete $s_lno $e_lno
 522         $ui_diff conf -state disabled
 523
 524         if {[$ui_diff get 1.0 end] eq "\n"} {
 525                 set o _
 526         } else {
 527                 set o ?
 528         }
 529
 530         if {$current_diff_side eq $ui_index} {
 531                 set mi ${o}M
 532         } elseif {[string index $mi 0] eq {_}} {
 533                 set mi M$o
 534         } else {
 535                 set mi ?$o
 536         }
 537         unlock_index
 538         display_file $current_diff_path $mi
 539         # This should trigger shift to the next changed file
 540         if {$o eq {_}} {
 541                 reshow_diff
 542         }
 543 }
 544
 545 proc apply_range_or_line {x y} {
 546         global current_diff_path current_diff_header current_diff_side
 547         global ui_diff ui_index file_states
 548
 549         set selected [$ui_diff tag nextrange sel 0.0]
 550
 551         if {$selected == {}} {
 552                 set first [$ui_diff index "@$x,$y"]
 553                 set last $first
 554         } else {
 555                 set first [lindex $selected 0]
 556                 set last [lindex $selected 1]
 557         }
 558
 559         set first_l [$ui_diff index "$first linestart"]
 560         set last_l [$ui_diff index "$last lineend"]
 561
 562         if {$current_diff_path eq {} || $current_diff_header eq {}} return
 563         if {![lock_index apply_hunk]} return
 564
 565         set apply_cmd {apply --cached --whitespace=nowarn}
 566         set mi [lindex $file_states($current_diff_path) 0]
 567         if {$current_diff_side eq $ui_index} {
 568                 set failed_msg [mc "Failed to unstage selected line."]
 569                 set to_context {+}
 570                 lappend apply_cmd --reverse
 571                 if {[string index $mi 0] ne {M}} {
 572                         unlock_index
 573                         return
 574                 }
 575         } else {
 576                 set failed_msg [mc "Failed to stage selected line."]
 577                 set to_context {-}
 578                 if {[string index $mi 1] ne {M}} {
 579                         unlock_index
 580                         return
 581                 }
 582         }
 583
 584         set wholepatch {}
 585
 586         while {$first_l < $last_l} {
 587                 set i_l [$ui_diff search -backwards -regexp ^@@ $first_l 0.0]
 588                 if {$i_l eq {}} {
 589                         # If there's not a @@ above, then the selected range
 590                         # must have come before the first_l @@
 591                         set i_l [$ui_diff search -regexp ^@@ $first_l $last_l]
 592                 }
 593                 if {$i_l eq {}} {
 594                         unlock_index
 595                         return
 596                 }
 597                 # $i_l is now at the beginning of a line
 598
 599                 # pick start line number from hunk header
 600                 set hh [$ui_diff get $i_l "$i_l + 1 lines"]
 601                 set hh [lindex [split $hh ,] 0]
 602                 set hln [lindex [split $hh -] 1]
 603
 604                 # There is a special situation to take care of. Consider this
 605                 # hunk:
 606                 #
 607                 #    @@ -10,4 +10,4 @@
 608                 #     context before
 609                 #    -old 1
 610                 #    -old 2
 611                 #    +new 1
 612                 #    +new 2
 613                 #     context after
 614                 #
 615                 # We used to keep the context lines in the order they appear in
 616                 # the hunk. But then it is not possible to correctly stage only
 617                 # "-old 1" and "+new 1" - it would result in this staged text:
 618                 #
 619                 #    context before
 620                 #    old 2
 621                 #    new 1
 622                 #    context after
 623                 #
 624                 # (By symmetry it is not possible to *un*stage "old 2" and "new
 625                 # 2".)
 626                 #
 627                 # We resolve the problem by introducing an asymmetry, namely,
 628                 # when a "+" line is *staged*, it is moved in front of the
 629                 # context lines that are generated from the "-" lines that are
 630                 # immediately before the "+" block. That is, we construct this
 631                 # patch:
 632                 #
 633                 #    @@ -10,4 +10,5 @@
 634                 #     context before
 635                 #    +new 1
 636                 #     old 1
 637                 #     old 2
 638                 #     context after
 639                 #
 640                 # But we do *not* treat "-" lines that are *un*staged in a
 641                 # special way.
 642                 #
 643                 # With this asymmetry it is possible to stage the change "old
 644                 # 1" -> "new 1" directly, and to stage the change "old 2" ->
 645                 # "new 2" by first staging the entire hunk and then unstaging
 646                 # the change "old 1" -> "new 1".
 647                 #
 648                 # Applying multiple lines adds complexity to the special
 649                 # situation.  The pre_context must be moved after the entire
 650                 # first block of consecutive staged "+" lines, so that
 651                 # staging both additions gives the following patch:
 652                 #
 653                 #    @@ -10,4 +10,6 @@
 654                 #     context before
 655                 #    +new 1
 656                 #    +new 2
 657                 #     old 1
 658                 #     old 2
 659                 #     context after
 660
 661                 # This is non-empty if and only if we are _staging_ changes;
 662                 # then it accumulates the consecutive "-" lines (after
 663                 # converting them to context lines) in order to be moved after
 664                 # "+" change lines.
 665                 set pre_context {}
 666
 667                 set n 0
 668                 set m 0
 669                 set i_l [$ui_diff index "$i_l + 1 lines"]
 670                 set patch {}
 671                 while {[$ui_diff compare $i_l < "end - 1 chars"] &&
 672                        [$ui_diff get $i_l "$i_l + 2 chars"] ne {@@}} {
 673                         set next_l [$ui_diff index "$i_l + 1 lines"]
 674                         set c1 [$ui_diff get $i_l]
 675                         if {[$ui_diff compare $first_l <= $i_l] &&
 676                             [$ui_diff compare $i_l < $last_l] &&
 677                             ($c1 eq {-} || $c1 eq {+})} {
 678                                 # a line to stage/unstage
 679                                 set ln [$ui_diff get $i_l $next_l]
 680                                 if {$c1 eq {-}} {
 681                                         set n [expr $n+1]
 682                                         set patch "$patch$pre_context$ln"
 683                                         set pre_context {}
 684                                 } else {
 685                                         set m [expr $m+1]
 686                                         set patch "$patch$ln"
 687                                 }
 688                         } elseif {$c1 ne {-} && $c1 ne {+}} {
 689                                 # context line
 690                                 set ln [$ui_diff get $i_l $next_l]
 691                                 set patch "$patch$pre_context$ln"
 692                                 set n [expr $n+1]
 693                                 set m [expr $m+1]
 694                                 set pre_context {}
 695                         } elseif {$c1 eq $to_context} {
 696                                 # turn change line into context line
 697                                 set ln [$ui_diff get "$i_l + 1 chars" $next_l]
 698                                 if {$c1 eq {-}} {
 699                                         set pre_context "$pre_context $ln"
 700                                 } else {
 701                                         set patch "$patch $ln"
 702                                 }
 703                                 set n [expr $n+1]
 704                                 set m [expr $m+1]
 705                         } else {
 706                                 # a change in the opposite direction of
 707                                 # to_context which is outside the range of
 708                                 # lines to apply.
 709                                 set patch "$patch$pre_context"
 710                                 set pre_context {}
 711                         }
 712                         set i_l $next_l
 713                 }
 714                 set patch "$patch$pre_context"
 715                 set wholepatch "$wholepatch@@ -$hln,$n +$hln,$m @@\n$patch"
 716                 set first_l [$ui_diff index "$next_l + 1 lines"]
 717         }
 718
 719         if {[catch {
 720                 set enc [get_path_encoding $current_diff_path]
 721                 set p [eval git_write $apply_cmd]
 722                 fconfigure $p -translation binary -encoding $enc
 723                 puts -nonewline $p $current_diff_header
 724                 puts -nonewline $p $wholepatch
 725                 close $p} err]} {
 726                 error_popup [append $failed_msg "\n\n$err"]
 727         }
 728
 729         unlock_index
 730 }