gitk: Unify handling of merge diffs with normal 2-way diffs

This adds code to getblobdiffline to make it able to recognize and
display merge diffs (i.e. N-way diffs for N >= 3) as well as normal
two-way diffs.  This means that it can also correctly display the
3-way diff of the local changes when the git repository is in the
middle of a merge with conflicts.

This also removes getmergediffline and changes mergediff to invoke
getblobdiffline rather than getmergediffline.

Signed-off-by: Paul Mackerras <paulus@samba.org>

gitk

@@ -2098,7 +2098,7 @@ proc makewindow {} {
     $ctext tag conf filesep -font textfontbold -back "#aaaaaa"
     $ctext tag conf hunksep -fore [lindex $diffcolors 2]
     $ctext tag conf d0 -fore [lindex $diffcolors 0]
-    $ctext tag conf d1 -fore [lindex $diffcolors 1]
+    $ctext tag conf dresult -fore [lindex $diffcolors 1]
     $ctext tag conf m0 -fore red
     $ctext tag conf m1 -fore blue
     $ctext tag conf m2 -fore green
@@ -3217,7 +3217,7 @@ proc find_hunk_blamespec {base line} {
 }
 
 proc external_blame_diff {} {
-    global currentid diffmergeid cmitmode
+    global currentid cmitmode
     global diff_menu_txtpos diff_menu_line
     global diff_menu_filebase flist_menu_file
 
@@ -6668,130 +6668,16 @@ proc mark_ctext_line {lnum} {
 }
 
 proc mergediff {id} {
-    global diffmergeid mdifffd
+    global diffmergeid
     global diffids treediffs
-    global parents
+    global parents curview
-    global diffcontext
-    global diffencoding
-    global limitdiffs vfilelimit curview
-    global targetline
 
     set diffmergeid $id
     set diffids $id
     set treediffs($id) {}
-    set targetline {}
-    # this doesn't seem to actually affect anything...
-    set cmd [concat | git diff-tree --no-commit-id --cc -U$diffcontext $id]
-    if {$limitdiffs && $vfilelimit($curview) ne {}} {
-	set cmd [concat $cmd -- $vfilelimit($curview)]
-    }
-    if {[catch {set mdf [open $cmd r]} err]} {
-	error_popup "[mc "Error getting merge diffs:"] $err"
-	return
-    }
-    fconfigure $mdf -blocking 0 -encoding binary
-    set mdifffd($id) $mdf
     set np [llength $parents($curview,$id)]
-    set diffencoding [get_path_encoding {}]
     settabs $np
-    filerun $mdf [list getmergediffline $mdf $id $np]
+    getblobdiffs $id
-}
-
-proc getmergediffline {mdf id np} {
-    global diffmergeid ctext cflist mergemax
-    global difffilestart mdifffd treediffs
-    global ctext_file_names ctext_file_lines
-    global diffencoding jump_to_here targetline diffline
-
-    $ctext conf -state normal
-    set nr 0
-    while {[incr nr] <= 1000 && [gets $mdf line] >= 0} {
-	if {![info exists diffmergeid] || $id != $diffmergeid
-	    || $mdf != $mdifffd($id)} {
-	    close $mdf
-	    return 0
-	}
-	if {[regexp {^diff --cc (.*)} $line match fname]} {
-	    # start of a new file
-	    set fname [encoding convertfrom $fname]
-	    $ctext insert end "\n"
-	    set here [$ctext index "end - 1c"]
-	    lappend difffilestart $here
-	    lappend treediffs($id) $fname
-	    add_flist [list $fname]
-	    lappend ctext_file_names $fname
-	    lappend ctext_file_lines [lindex [split $here "."] 0]
-	    set diffencoding [get_path_encoding $fname]
-	    set l [expr {(78 - [string length $fname]) / 2}]
-	    set pad [string range "----------------------------------------" 1 $l]
-	    $ctext insert end "$pad $fname $pad\n" filesep
-	    set targetline {}
-	    if {$jump_to_here ne {} && [lindex $jump_to_here 0] eq $fname} {
-		set targetline [lindex $jump_to_here 1]
-	    }
-	    set diffline 0
-	} elseif {[regexp {^@@} $line]} {
-	    set line [encoding convertfrom $diffencoding $line]
-	    $ctext insert end "$line\n" hunksep
-	    if {[regexp { \+(\d+),\d+ @@} $line m nl]} {
-		set diffline $nl
-	    }
-	} elseif {[regexp {^[0-9a-f]{40}$} $line] || [regexp {^index} $line]} {
-	    # do nothing
-	} else {
-	    set line [encoding convertfrom $diffencoding $line]
-	    # parse the prefix - one ' ', '-' or '+' for each parent
-	    set spaces {}
-	    set minuses {}
-	    set pluses {}
-	    set isbad 0
-	    for {set j 0} {$j < $np} {incr j} {
-		set c [string range $line $j $j]
-		if {$c == " "} {
-		    lappend spaces $j
-		} elseif {$c == "-"} {
-		    lappend minuses $j
-		} elseif {$c == "+"} {
-		    lappend pluses $j
-		} else {
-		    set isbad 1
-		    break
-		}
-	    }
-	    set tags {}
-	    set num {}
-	    if {!$isbad && $minuses ne {} && $pluses eq {}} {
-		# line doesn't appear in result, parents in $minuses have the line
-		set num [lindex $minuses 0]
-	    } elseif {!$isbad && $pluses ne {} && $minuses eq {}} {
-		# line appears in result, parents in $pluses don't have the line
-		lappend tags mresult
-		set num [lindex $spaces 0]
-	    }
-	    if {$num ne {}} {
-		if {$num >= $mergemax} {
-		    set num "max"
-		}
-		lappend tags m$num
-	    }
-	    $ctext insert end "$line\n" $tags
-	    if {$targetline ne {} && $minuses eq {}} {
-		if {$diffline == $targetline} {
-		    set here [$ctext index "end - 1 line"]
-		    mark_ctext_line [lindex [split $here .] 0]
-		    set targetline {}
-		} else {
-		    incr diffline
-		}
-	    }
-	}
-    }
-    $ctext conf -state disabled
-    if {[eof $mdf]} {
-	close $mdf
-	return 0
-    }
-    return [expr {$nr >= 1000? 2: 1}]
 }
 
 proc startdiff {ids} {
@@ -6971,9 +6857,9 @@ proc getblobdiffs {ids} {
     global diffcontext
     global ignorespace
     global limitdiffs vfilelimit curview
-    global diffencoding targetline
+    global diffencoding targetline diffnparents
 
-    set cmd [diffcmd $ids "-p -C --no-commit-id -U$diffcontext"]
+    set cmd [diffcmd $ids "-p -C --cc --no-commit-id -U$diffcontext"]
     if {$ignorespace} {
 	append cmd " -w"
     }
@@ -6981,10 +6867,11 @@ proc getblobdiffs {ids} {
 	set cmd [concat $cmd -- $vfilelimit($curview)]
     }
     if {[catch {set bdf [open $cmd r]} err]} {
-	puts "error getting diffs: $err"
+	error_popup [mc "Error getting diffs: %s" $err]
 	return
     }
     set targetline {}
+    set diffnparents 0
     set diffinhdr 0
     set diffencoding [get_path_encoding {}]
     fconfigure $bdf -blocking 0 -encoding binary
@@ -7006,9 +6893,11 @@ proc setinlist {var i val} {
 }
 
 proc makediffhdr {fname ids} {
-    global ctext curdiffstart treediffs
+    global ctext curdiffstart treediffs diffencoding
     global ctext_file_names jump_to_here targetline diffline
 
+    set fname [encoding convertfrom $fname]
+    set diffencoding [get_path_encoding $fname]
     set i [lsearch -exact $treediffs($ids) $fname]
     if {$i >= 0} {
 	setinlist difffilestart $i $curdiffstart
@@ -7028,7 +6917,7 @@ proc getblobdiffline {bdf ids} {
     global diffids blobdifffd ctext curdiffstart
     global diffnexthead diffnextnote difffilestart
     global ctext_file_names ctext_file_lines
-    global diffinhdr treediffs
+    global diffinhdr treediffs mergemax diffnparents
     global diffencoding jump_to_here targetline diffline
 
     set nr 0
@@ -7038,47 +6927,63 @@ proc getblobdiffline {bdf ids} {
 	    close $bdf
 	    return 0
 	}
-	if {![string compare -length 11 "diff --git " $line]} {
+	if {![string compare -length 5 "diff " $line]} {
-	    # trim off "diff --git "
+	    if {![regexp {^diff (--cc|--git) } $line m type]} {
-	    set line [string range $line 11 end]
+		set line [encoding convertfrom $line]
-	    set diffinhdr 1
+		$ctext insert end "$line\n" hunksep
+		continue
+	    }
 	    # start of a new file
+	    set diffinhdr 1
 	    $ctext insert end "\n"
 	    set curdiffstart [$ctext index "end - 1c"]
 	    lappend ctext_file_names ""
 	    lappend ctext_file_lines [lindex [split $curdiffstart "."] 0]
 	    $ctext insert end "\n" filesep
-	    # If the name hasn't changed the length will be odd,
+
-	    # the middle char will be a space, and the two bits either
+	    if {$type eq "--cc"} {
-	    # side will be a/name and b/name, or "a/name" and "b/name".
+		# start of a new file in a merge diff
-	    # If the name has changed we'll get "rename from" and
+		set fname [string range $line 10 end]
-	    # "rename to" or "copy from" and "copy to" lines following this,
+		if {[lsearch -exact $treediffs($ids) $fname] < 0} {
-	    # and we'll use them to get the filenames.
+		    lappend treediffs($ids) $fname
-	    # This complexity is necessary because spaces in the filename(s)
+		    add_flist [list $fname]
-	    # don't get escaped.
+		}
-	    set l [string length $line]
+
-	    set i [expr {$l / 2}]
-	    if {!(($l & 1) && [string index $line $i] eq " " &&
-		  [string range $line 2 [expr {$i - 1}]] eq \
-		      [string range $line [expr {$i + 3}] end])} {
-		continue
-	    }
-	    # unescape if quoted and chop off the a/ from the front
-	    if {[string index $line 0] eq "\""} {
-		set fname [string range [lindex $line 0] 2 end]
 	    } else {
-		set fname [string range $line 2 [expr {$i - 1}]]
+		set line [string range $line 11 end]
+		# If the name hasn't changed the length will be odd,
+		# the middle char will be a space, and the two bits either
+		# side will be a/name and b/name, or "a/name" and "b/name".
+		# If the name has changed we'll get "rename from" and
+		# "rename to" or "copy from" and "copy to" lines following
+		# this, and we'll use them to get the filenames.
+		# This complexity is necessary because spaces in the
+		# filename(s) don't get escaped.
+		set l [string length $line]
+		set i [expr {$l / 2}]
+		if {!(($l & 1) && [string index $line $i] eq " " &&
+		      [string range $line 2 [expr {$i - 1}]] eq \
+			  [string range $line [expr {$i + 3}] end])} {
+		    continue
+		}
+		# unescape if quoted and chop off the a/ from the front
+		if {[string index $line 0] eq "\""} {
+		    set fname [string range [lindex $line 0] 2 end]
+		} else {
+		    set fname [string range $line 2 [expr {$i - 1}]]
+		}
 	    }
-	    set fname [encoding convertfrom $fname]
-	    set diffencoding [get_path_encoding $fname]
 	    makediffhdr $fname $ids
 
-	} elseif {[regexp {^@@ -([0-9]+)(,[0-9]+)? \+([0-9]+)(,[0-9]+)? @@(.*)} \
+	} elseif {![string compare -length 2 "@@" $line]} {
-		       $line match f1l f1c f2l f2c rest]} {
+	    regexp {^@@+} $line ats
 	    set line [encoding convertfrom $diffencoding $line]
 	    $ctext insert end "$line\n" hunksep
+	    if {[regexp { \+(\d+),\d+ @@} $line m nl]} {
+		set diffline $nl
+	    }
+	    set diffnparents [expr {[string length $ats] - 1}]
 	    set diffinhdr 0
-	    set diffline $f2l
 
 	} elseif {$diffinhdr} {
 	    if {![string compare -length 12 "rename from " $line]} {
@@ -7097,8 +7002,6 @@ proc getblobdiffline {bdf ids} {
 		if {[string index $fname 0] eq "\""} {
 		    set fname [lindex $fname 0]
 		}
-		set fname [encoding convertfrom $fname]
-		set diffencoding [get_path_encoding $fname]
 		makediffhdr $fname $ids
 	    } elseif {[string compare -length 3 $line "---"] == 0} {
 		# do nothing
@@ -7111,28 +7014,53 @@ proc getblobdiffline {bdf ids} {
 
 	} else {
 	    set line [encoding convertfrom $diffencoding $line]
-	    set x [string range $line 0 0]
+	    # parse the prefix - one ' ', '-' or '+' for each parent
-	    set here [$ctext index "end - 1 chars"]
+	    set prefix [string range $line 0 [expr {$diffnparents - 1}]]
-	    if {$x == "-" || $x == "+"} {
+	    set tag [expr {$diffnparents > 1? "m": "d"}]
-		set tag [expr {$x == "+"}]
+	    if {[string trim $prefix " -+"] eq {}} {
-		$ctext insert end "$line\n" d$tag
+		# prefix only has " ", "-" and "+" in it: normal diff line
-	    } elseif {$x == " "} {
+		set num [string first "-" $prefix]
-		$ctext insert end "$line\n"
+		if {$num >= 0} {
+		    # removed line, first parent with line is $num
+		    if {$num >= $mergemax} {
+			set num "max"
+		    }
+		    $ctext insert end "$line\n" $tag$num
+		} else {
+		    set tags {}
+		    if {[string first "+" $prefix] >= 0} {
+			# added line
+			lappend tags ${tag}result
+			if {$diffnparents > 1} {
+			    set num [string first " " $prefix]
+			    if {$num >= 0} {
+				if {$num >= $mergemax} {
+				    set num "max"
+				}
+				lappend tags m$num
+			    }
+			}
+		    }
+		    if {$targetline ne {}} {
+			if {$diffline == $targetline} {
+			    set seehere [$ctext index "end - 1 chars"]
+			    set targetline {}
+			} else {
+			    incr diffline
+			}
+		    }
+		    $ctext insert end "$line\n" $tags
+		}
 	    } else {
 		# "\ No newline at end of file",
 		# or something else we don't recognize
 		$ctext insert end "$line\n" hunksep
 	    }
-	    if {$targetline ne {} && ($x eq " " || $x eq "+")} {
-		if {$diffline == $targetline} {
-		    mark_ctext_line [lindex [split $here .] 0]
-		    set targetline {}
-		} else {
-		    incr diffline
-		}
-	    }
 	}
     }
+    if {[info exists seehere]} {
+	mark_ctext_line [lindex [split $seehere .] 0]
+    }
     $ctext conf -state disabled
     if {[eof $bdf]} {
 	close $bdf
@@ -7145,7 +7073,7 @@ proc changediffdisp {} {
     global ctext diffelide
 
     $ctext tag conf d0 -elide [lindex $diffelide 0]
-    $ctext tag conf d1 -elide [lindex $diffelide 1]
+    $ctext tag conf dresult -elide [lindex $diffelide 1]
 }
 
 proc highlightfile {loc cline} {
@@ -9817,7 +9745,7 @@ proc doprefs {} {
     label $top.diffnew -padx 40 -relief sunk -background [lindex $diffcolors 1]
     button $top.diffnewbut -text [mc "Diff: new lines"] -font optionfont \
 	-command [list choosecolor diffcolors 1 $top.diffnew "diff new lines" \
-		      [list $ctext tag conf d1 -foreground]]
+		      [list $ctext tag conf dresult -foreground]]
     grid x $top.diffnewbut $top.diffnew -sticky w
     label $top.hunksep -padx 40 -relief sunk -background [lindex $diffcolors 2]
     button $top.hunksepbut -text [mc "Diff: hunk header"] -font optionfont \