gitk: Improve handling of whitespace and special chars in filenames

The main thing here is better parsing of the diff --git lines in the
output of git diff-tree -p.  We now cope with filenames in quotes with
special chars escaped.  If the filenames contain spaces they aren't
quoted, however, which can create difficulties in parsing.  We get
around the difficulties by detecting the case when the filename hasn't
changed (chop the part after "diff --git " in two and see if the halves
match apart from a/ in one and b/ in the other), and if it hasn't
changed, we just use one half.  If the filename has changed we wait
for the "rename from" and "rename to" lines, which give the old and
new filenames unambiguously.

This also improves the parsing of the output of git diff-tree.
Instead of using lindex to extract the filename, we take the part from
the first tab on, and if it starts with a quote, we use [lindex $str 0]
to remove the quotes and convert the escapes.

This also gets rid of some unused tagging of the diff text, uses
[string compare] instead of [regexp] in some places, and fixes the
regexp for detecting the @@ hunk-separator lines (the regexp wasn't
accepting a single number, as in "-0,0 +1" for example).
Signed-off-by: NPaul Mackerras <paulus@samba.org>

gitk

@@ -4400,7 +4400,6 @@ proc selectline {l isnew} {
     }
     appendwithlinks $comment {comment}
 
-    $ctext tag delete Comments
     $ctext tag remove found 1.0 end
     $ctext conf -state disabled
     set commentend [$ctext index "end - 1c"]
@@ -4566,10 +4565,11 @@ proc gettreeline {gtf id} {
     set nl 0
     while {[incr nl] <= 1000 && [gets $gtf line] >= 0} {
 	if {$diffids ne $nullid} {
-	    set tl [split $line "\t"]
-	    if {[lindex $tl 0 1] ne "blob"} continue
-	    set sha1 [lindex $tl 0 2]
-	    set fname [lindex $tl 1]
+	    if {[lindex $line 1] ne "blob"} continue
+	    set i [string first "\t" $line]
+	    if {$i < 0} continue
+	    set sha1 [lindex $line 2]
+	    set fname [string range $line [expr {$i+1}] end]
 	    if {[string index $fname 0] eq "\""} {
 		set fname [lindex $fname 0]
 	    }
@@ -4797,8 +4797,14 @@ proc gettreediffline {gdtf ids} {
 
     set nr 0
     while {[incr nr] <= 1000 && [gets $gdtf line] >= 0} {
-	set file [lindex $line 5]
-	lappend treediff $file
+	set i [string first "\t" $line]
+	if {$i >= 0} {
+	    set file [string range $line [expr {$i+1}] end]
+	    if {[string index $file 0] eq "\""} {
+		set file [lindex $file 0]
+	    }
+	    lappend treediff $file
+	}
     }
     if {![eof $gdtf]} {
 	return [expr {$nr >= 1000? 2: 1}]
@@ -4819,7 +4825,7 @@ proc gettreediffline {gdtf ids} {
 }
 
 proc getblobdiffs {ids} {
-    global diffopts blobdifffd diffids env curdifftag curtagstart
+    global diffopts blobdifffd diffids env
     global diffinhdr treediffs
 
     set env(GIT_DIFF_OPTS) $diffopts
@@ -4830,8 +4836,6 @@ proc getblobdiffs {ids} {
     set diffinhdr 0
     fconfigure $bdf -blocking 0
     set blobdifffd($ids) $bdf
-    set curdifftag Comments
-    set curtagstart 0.0
     filerun $bdf [list getblobdiffline $bdf $diffids]
 }
 
@@ -4848,8 +4852,20 @@ proc setinlist {var i val} {
     }
 }
 
+proc makediffhdr {fname ids} {
+    global ctext curdiffstart treediffs
+
+    set i [lsearch -exact $treediffs($ids) $fname]
+    if {$i >= 0} {
+	setinlist difffilestart $i $curdiffstart
+    }
+    set l [expr {(78 - [string length $fname]) / 2}]
+    set pad [string range "----------------------------------------" 1 $l]
+    $ctext insert $curdiffstart "$pad $fname $pad" filesep
+}
+
 proc getblobdiffline {bdf ids} {
-    global diffids blobdifffd ctext curdifftag curtagstart
+    global diffids blobdifffd ctext curdiffstart
     global diffnexthead diffnextnote difffilestart
     global diffinhdr treediffs
 
@@ -4860,38 +4876,67 @@ proc getblobdiffline {bdf ids} {
 	    close $bdf
 	    return 0
 	}
-	if {[regexp {^diff --git a/(.*) b/(.*)} $line match fname newname]} {
+	if {![string compare -length 11 "diff --git " $line]} {
+	    # trim off "diff --git "
+	    set line [string range $line 11 end]
+	    set diffinhdr 1
 	    # start of a new file
 	    $ctext insert end "\n"
-	    $ctext tag add $curdifftag $curtagstart end
-	    set here [$ctext index "end - 1c"]
-	    set curtagstart $here
-	    set header $newname
-	    set i [lsearch -exact $treediffs($ids) $fname]
-	    if {$i >= 0} {
-		setinlist difffilestart $i $here
+	    set curdiffstart [$ctext index "end - 1c"]
+	    $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
+	    # 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" 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
 	    }
-	    if {$newname ne $fname} {
-		set i [lsearch -exact $treediffs($ids) $newname]
-		if {$i >= 0} {
-		    setinlist difffilestart $i $here
-		}
+	    # 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 curdifftag "f:$fname"
-	    $ctext tag delete $curdifftag
-	    set l [expr {(78 - [string length $header]) / 2}]
-	    set pad [string range "----------------------------------------" \
-			 1 $l]
-	    $ctext insert end "$pad $header $pad\n" filesep
-	    set diffinhdr 1
-	} elseif {$diffinhdr && [string compare -length 3 $line "---"] == 0} {
-	    # do nothing
-	} elseif {$diffinhdr && [string compare -length 3 $line "+++"] == 0} {
-	    set diffinhdr 0
-	} elseif {[regexp {^@@ -([0-9]+),([0-9]+) \+([0-9]+),([0-9]+) @@(.*)} \
+	    makediffhdr $fname $ids
+
+	} elseif {[regexp {^@@ -([0-9]+)(,[0-9]+)? \+([0-9]+)(,[0-9]+)? @@(.*)} \
 		       $line match f1l f1c f2l f2c rest]} {
 	    $ctext insert end "$line\n" hunksep
 	    set diffinhdr 0
+
+	} elseif {$diffinhdr} {
+	    if {![string compare -length 12 "rename from " $line]} {
+		set fname [string range $line 12 end]
+		if {[string index $fname 0] eq "\""} {
+		    set fname [lindex $fname 0]
+		}
+		set i [lsearch -exact $treediffs($ids) $fname]
+		if {$i >= 0} {
+		    setinlist difffilestart $i $curdiffstart
+		}
+	    } elseif {![string compare -length 10 $line "rename to "]} {
+		set fname [string range $line 10 end]
+		if {[string index $fname 0] eq "\""} {
+		    set fname [lindex $fname 0]
+		}
+		makediffhdr $fname $ids
+	    } elseif {[string compare -length 3 $line "---"] == 0} {
+		# do nothing
+		continue
+	    } elseif {[string compare -length 3 $line "+++"] == 0} {
+		set diffinhdr 0
+		continue
+	    }
+	    $ctext insert end "$line\n" filesep
+
 	} else {
 	    set x [string range $line 0 0]
 	    if {$x == "-" || $x == "+"} {
@@ -4899,27 +4944,16 @@ proc getblobdiffline {bdf ids} {
 		$ctext insert end "$line\n" d$tag
 	    } elseif {$x == " "} {
 		$ctext insert end "$line\n"
-	    } elseif {$diffinhdr || $x == "\\"} {
-		# e.g. "\ No newline at end of file"
-		$ctext insert end "$line\n" filesep
 	    } else {
-		# Something else we don't recognize
-		if {$curdifftag != "Comments"} {
-		    $ctext insert end "\n"
-		    $ctext tag add $curdifftag $curtagstart end
-		    set curtagstart [$ctext index "end - 1c"]
-		    set curdifftag Comments
-		}
-		$ctext insert end "$line\n" filesep
+		# "\ No newline at end of file",
+		# or something else we don't recognize
+		$ctext insert end "$line\n" hunksep
 	    }
 	}
     }
     $ctext conf -state disabled
     if {[eof $bdf]} {
 	close $bdf
-	if {$ids == $diffids && $bdf == $blobdifffd($ids)} {
-	    $ctext tag add $curdifftag $curtagstart end
-	}
 	return 0
     }
     return [expr {$nr >= 1000? 2: 1}]
@@ -5444,7 +5478,6 @@ proc doseldiff {oldid newid} {
     $ctext insert end [lindex $commitinfo($newid) 0]
     $ctext insert end "\n"
     $ctext conf -state disabled
-    $ctext tag delete Comments
     $ctext tag remove found 1.0 end
     startdiff [list $oldid $newid]
 }