git-gui: Show a round number of bytes of large untracked text files

If an untracked text file is selected, then its contents are displayed
instead of a diff. If the file is large, then the following hint is
inserted at the top:

  * Untracked file is 14774881 bytes.
  * Showing only first 131072 bytes.

Why exactly 131072 bytes? With this patch it is 100000 bytes.
Signed-off-by: NJohannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>

lib/diff.tcl

@@ -164,7 +164,7 @@ proc show_other_diff {path w m cont_info} {
 	# - 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 type [file type $path]