rename vipsthumbnail -o as -f

-o stays as a hidden flag

see https://github.com/jcupitt/libvips/issues/216

ChangeLog

@@ -11,6 +11,7 @@
 - vipsthumbnail will return an error code if one or more conversions failed
 - disable chroma subsample in jpeg-tiff if Q >= 90
 - try to handle tiffs with old-style 8-bit colormaps
+- rename vipsthumbnail -o as -f, -o stays as a hidden flag
 
 24/12/14 started 7.42.1
 - add gobject-2.0 to Requires: in vips and vips-cpp .pc files

man/vipsthumbnail.1

@@ -26,7 +26,7 @@ and write thumbnails to the files
 and
 .B tn_jim.jpg.
 
- $ vipsthumbnail --size=64 -o thumbnails/%s.png fred.jpg
+ $ vipsthumbnail --size=64 -f thumbnails/%s.png fred.jpg
 
 will read image file
 .B fred.jpg
@@ -45,7 +45,7 @@ The image is shrunk so that it just fits within this area, images
 which are smaller than this are expanded.
 
 .TP
-.B -o FORMAT, --output=FORMAT     
+.B -f FORMAT, --format=FORMAT     
 Set the output format string. The input filename has any file type suffix
 removed, then that value is substitued into 
 .B FORMAT

tools/vipsthumbnail.c

@@ -63,6 +63,8 @@
  * 	  profile
  * 13/1/15
  * 	- exit with an error code if one or more conversions failed
+ * 20/1/15
+ * 	- rename -o as -f, keep -o as a hidden flag
  */
 
 #ifdef HAVE_CONFIG_H
@@ -109,10 +111,14 @@ static GOptionEntry options[] = {
 		G_OPTION_ARG_STRING, &thumbnail_size, 
 		N_( "shrink to SIZE or to WIDTHxHEIGHT" ), 
 		N_( "SIZE" ) },
-	{ "output", 'o', 0, 
+	{ "output", 'o', G_OPTION_FLAG_HIDDEN, 
 		G_OPTION_ARG_STRING, &output_format, 
 		N_( "set output to FORMAT" ), 
 		N_( "FORMAT" ) },
+	{ "format", 'f', 0, 
+		G_OPTION_ARG_STRING, &output_format, 
+		N_( "set output format string to FORMAT" ), 
+		N_( "FORMAT" ) },
 	{ "interpolator", 'p', 0, 
 		G_OPTION_ARG_STRING, &interpolator, 
 		N_( "resample with INTERPOLATOR" ),