git-gui: ensure the file in the diff pane is in the list of selected files
[gitweb.git] / lib / diff.tcl
index 9cb9d0604a4905337dc0c57d8d846753a3157c8a..30bdd691ee0447a0498e0ec06c1bcaa3379c2d3c 100644 (file)
@@ -1,6 +1,19 @@
 # git-gui diff viewer
 # Copyright (C) 2006, 2007 Shawn Pearce
 
+proc apply_tab_size {{firsttab {}}} {
+       global have_tk85 repo_config ui_diff
+
+       set w [font measure font_diff "0"]
+       if {$have_tk85 && $firsttab != 0} {
+               $ui_diff configure -tabs [list [expr {$firsttab * $w}] [expr {($firsttab + $repo_config(gui.tabsize)) * $w}]]
+       } elseif {$have_tk85 || $repo_config(gui.tabsize) != 8} {
+               $ui_diff configure -tabs [expr {$repo_config(gui.tabsize) * $w}]
+       } else {
+               $ui_diff configure -tabs {}
+       }
+}
+
 proc clear_diff {} {
        global ui_diff current_diff_path current_diff_header
        global ui_index ui_workdir
@@ -16,47 +29,70 @@ proc clear_diff {} {
        $ui_workdir tag remove in_diff 0.0 end
 }
 
-proc reshow_diff {} {
+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 {}
-               || [catch {set s $file_states($p)}]
-               || [lsearch -sorted -exact $file_lists($current_diff_side) $p] == -1} {
+       } elseif {$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 {
-               show_diff $p $current_diff_side
+               set save_pos [lindex [$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}} return
+       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 "No differences detected.
+       info_popup [mc "No differences detected.
 
-[short_path $path] has no changes.
+%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."
+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 {}}} {
+proc show_diff {path w {lno {}} {scroll_pos {}} {callback {}}} {
        global file_states file_lists
-       global is_3way_diff diff_active repo_config
+       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
 
@@ -69,138 +105,352 @@ proc show_diff {path w {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_3way_diff 0
-       set diff_active 1
+       set is_conflict_diff 0
        set current_diff_path $path
        set current_diff_side $w
-       set current_diff_header {}
-       ui_status "Loading diff of [escape_path $path]..."
+       set current_diff_queue {}
+       ui_status [mc "Loading diff of %s..." [escape_path $path]]
+
+       set cont_info [list $scroll_pos $callback]
+
+       apply_tab_size 0
+
+       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 $cont_info
+       }
+
+       global current_diff_path selected_paths
+       set selected_paths($current_diff_path) 1
+}
+
+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 [expr {128 * 1024}]
+               set max_sz 100000
+               set type unknown
                if {[catch {
-                               set fd [open $path r]
-                               set content [read $fd $max_sz]
-                               close $fd
-                               set sz [file size $path]
+                               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 "Unable to display [escape_path $path]"
-                       error_popup "Error loading file:\n\n$err"
+                       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 {![catch {set type [exec file $path]}]} {
+               if {$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_@
+                       $ui_diff insert end "* $type\n" d_info
                }
                if {[string first "\0" $content] != -1} {
                        $ui_diff insert end \
-                               "* Binary file (not showing content)." \
-                               d_@
+                               [mc "* Binary file (not showing content)."] \
+                               d_info
                } else {
                        if {$sz > $max_sz} {
-                               $ui_diff insert end \
-"* Untracked file is $sz bytes.
-* Showing only first $max_sz bytes.
-" d_@
+                               $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 "
-* Untracked file clipped here by [appname].
+                               $ui_diff insert end [mc "
+* Untracked file clipped here by %s.
 * To see the entire file, use an external editor.
-" d_@
+" [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 $ui_index} {
                lappend cmd diff-index
                lappend cmd --cached
+               if {[git-version >= "1.7.2"]} {
+                       lappend cmd --ignore-submodules=dirty
+               }
        } elseif {$w eq $ui_workdir} {
-               if {[string index $m 0] eq {U}} {
+               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 --no-color
-       if {$repo_config(gui.diffcontext) >= 0} {
+       lappend cmd --color
+       set cmd [concat $cmd $repo_config(gui.diffopts)]
+       if {$repo_config(gui.diffcontext) >= 1} {
                lappend cmd "-U$repo_config(gui.diffcontext)"
        }
        if {$w eq $ui_index} {
                lappend cmd [PARENT]
        }
-       lappend cmd --
-       lappend cmd $path
+       if {$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 "Unable to display [escape_path $path]"
-               error_popup "Error loading diff:\n\n$err"
+               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 binary \
-               -translation binary
-       fileevent $fd readable [list read_diff $fd]
+               -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} {
-       global ui_diff diff_active
-       global is_3way_diff current_diff_header
+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} {
-               # -- Cleanup uninteresting diff header lines.
-               #
+               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]
-                       || [string match {--- *}             $line]
-                       || [string match {+++ *}             $line]} {
-                       append current_diff_header $line "\n"
-                       continue
-               }
-               if {[string match {index *} $line]} continue
-               if {$line eq {deleted file mode 120000}} {
-                       set line "deleted symlink"
+                   || [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 {[string match {mode *} $line]
-                       || [string match {new file *} $line]
-                       || [string match {deleted file *} $line]
-                       || [string match {Binary files * and * differ} $line]
-                       || $line eq {\ No newline at end of file}
-                       || [regexp {^\* Unmerged path } $line]} {
-                       set tags {}
+               if {[string match {@@@ *} $line]} {
+                       set is_3way_diff 1
+                       apply_tab_size 1
+               }
+
+               if {$::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 {
@@ -212,7 +462,10 @@ proc read_diff {fd} {
                        {- } {set tags d_-s}
                        {--} {set tags d_--}
                        {++} {
-                               if {[regexp {^\+\+([<>]{7} |={7})} $line _g op]} {
+                               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 {
@@ -224,6 +477,25 @@ proc read_diff {fd} {
                                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 {
@@ -231,8 +503,10 @@ proc read_diff {fd} {
                        {@} {set tags d_@}
                        {-} {set tags d_-}
                        {+} {
-                               if {[regexp {^\+([<>]{7} |={7})} $line _g op]} {
-                                       set line [string replace $line 0 0 { }]
+                               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_+
@@ -244,22 +518,52 @@ proc read_diff {fd} {
                        }
                        }
                }
+               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 [lsort -integer [split $colbegin ";"]] {
+                               if {$style eq "7"} {append prefix i; continue}
+                               if {$style != 4 && ($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
                }
        }
 }
@@ -274,14 +578,14 @@ proc apply_hunk {x y} {
        set apply_cmd {apply --cached --whitespace=nowarn}
        set mi [lindex $file_states($current_diff_path) 0]
        if {$current_diff_side eq $ui_index} {
-               set mode unstage
+               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 mode stage
+               set failed_msg [mc "Failed to stage selected hunk."]
                if {[string index $mi 1] ne {M}} {
                        unlock_index
                        return
@@ -301,12 +605,13 @@ proc apply_hunk {x y} {
        }
 
        if {[catch {
+               set enc [get_path_encoding $current_diff_path]
                set p [eval git_write $apply_cmd]
-               fconfigure $p -translation binary -encoding binary
+               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 "Failed to $mode selected hunk.\n\n$err"
+               error_popup [append $failed_msg "\n\n$err"]
                unlock_index
                return
        }
@@ -330,7 +635,202 @@ proc apply_hunk {x y} {
        }
        unlock_index
        display_file $current_diff_path $mi
+       # This should trigger shift to the next changed file
        if {$o eq {_}} {
-               clear_diff
+               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"
+                               # Skip the "\ No newline at end of
+                               # file". Depending on the locale setting
+                               # we don't know what this line looks
+                               # like exactly. The only thing we do
+                               # know is that it starts with "\ "
+                               if {![string match {\\ *} $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
 }