Regenerate manual

MANUAL.txt

@@ -1,4 +1,4 @@
-oxipng 9.0.0
+oxipng 9.1.0
 Losslessly improve compression of PNG files
 
 Usage: oxipng [OPTIONS] <files>...
@@ -64,8 +64,14 @@ Options:
           Note that 'bKGD', 'sBIT' and 'hIST' will be forcibly stripped if the color type or bit
           depth is changed, regardless of any options set.
           
+          The default when --strip is not passed is to keep all metadata.
+
       --keep <list>
-          Strip all metadata except in the comma-separated list
+          Strip all metadata chunks except those in the comma-separated list. The special value
+          'display' includes chunks that affect the image appearance, equivalent to '--strip safe'.
+          
+          E.g. '--keep eXIf,display' will strip chunks, keeping only eXIf and those that affect the
+          image appearance.
 
   -a, --alpha
           Perform additional optimization on images with an alpha channel, by altering the color
@@ -110,6 +116,7 @@ Options:
               2  =>  Up
               3  =>  Average
               4  =>  Paeth
+          
           Heuristic strategies (try to find the best delta filter for each line)
               5  =>  MinSum    Minimum sum of absolute differences
               6  =>  Entropy   Highest Shannon entropy