lavfi/testsrc: add "d" alias for the duration option

doc/filters.texi

@@ -3230,7 +3230,7 @@ number or a valid video frame rate abbreviation. The default value is
 @item sar
 Set the sample aspect ratio of the sourced video.
 
-@item duration
+@item duration, d
 Set the video duration of the sourced video. The accepted syntax is:
 @example
 [-]HH[:MM[:SS[.m...]]]

libavfilter/avfilter.h

@@ -31,7 +31,7 @@
 
 #define LIBAVFILTER_VERSION_MAJOR  2
 #define LIBAVFILTER_VERSION_MINOR 58
-#define LIBAVFILTER_VERSION_MICRO 100
+#define LIBAVFILTER_VERSION_MICRO 101
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \

libavfilter/vsrc_testsrc.c

@@ -62,6 +62,7 @@ static const AVOption testsrc_options[]= {
     { "rate",     "set video rate",     OFFSET(rate),     AV_OPT_TYPE_STRING, {.str = "25"},      0, 0 },
     { "r",        "set video rate",     OFFSET(rate),     AV_OPT_TYPE_STRING, {.str = "25"},      0, 0 },
     { "duration", "set video duration", OFFSET(duration), AV_OPT_TYPE_STRING, {.str = NULL},      0, 0 },
+    { "d",        "set video duration", OFFSET(duration), AV_OPT_TYPE_STRING, {.str = NULL},      0, 0 },
     { "sar",      "set video sample aspect ratio", OFFSET(sar), AV_OPT_TYPE_RATIONAL, {.dbl= 1},  0, INT_MAX },
     { NULL },
 };