patch 9.1.0857: xxd: --- is incorrectly recognized as end-of-options

Problem:  xxd: --- is incorrectly recognized as end-of-options
Solution: improve xxds end-of-option parser (DungSaga)

closes: #9285

Signed-off-by: DungSaga <dungsaga@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/testdir/test_xxd.vim

@@ -356,7 +356,7 @@ endfunc
 
 " Various ways with wrong arguments that trigger the usage output.
 func Test_xxd_usage()
-  for arg in ['-h', '-c', '-g', '-o', '-s', '-l', '-X', '-R', 'one two three']
+  for arg in ['-h', '-c', '-g', '-o', '-s', '-l', '-X', '-R', 'one two three', '----', '---']
     new
     exe 'r! ' . s:xxd_cmd . ' ' . arg
     call assert_match("Usage:", join(getline(1, 3)))
@@ -364,6 +364,13 @@ func Test_xxd_usage()
   endfor
 endfunc
 
+func Test_xxd_end_of_options()
+  new
+  exe 'r! ' . s:xxd_cmd . ' -- random-file-' . rand()
+  call assert_match('random-file-.*: No such file or directory', join(getline(1, 3)))
+  bwipe!
+endfunc
+
 func Test_xxd_ignore_garbage()
   new
   exe 'r! printf "\n\r xxxx 0: 42 42" | ' . s:xxd_cmd . ' -r'

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    857,
 /**/
     856,
 /**/

src/xxd/xxd.c

@@ -65,6 +65,7 @@
  * 10.05.2024  fix another buffer-overflow when writing colored output to buffer, #14738
  * 10.09.2024  Support -b and -i together, #15661
  * 19.10.2024  -e did add an extra space #15899
+ * 11.11.2024  improve end-of-options argument parser #9285
  *
  * (c) 1990-1998 by Juergen Weigert (jnweiger@gmail.com)
  *
@@ -145,7 +146,7 @@ extern void perror __P((char *));
 # endif
 #endif
 
-char version[] = "xxd 2024-10-19 by Juergen Weigert et al.";
+char version[] = "xxd 2024-11-11 by Juergen Weigert et al.";
 #ifdef WIN32
 char osver[] = " (Win32)";
 #else
@@ -843,7 +844,7 @@ main(int argc, char *argv[])
 	  else
 	    exit_with_usage();
         }
-      else if (!strcmp(pp, "--"))	/* end of options */
+      else if (!strcmp(argv[1], "--"))	/* end of options */
 	{
 	  argv++;
 	  argc--;