patch 8.1.0821: xxd "usage" output and other arguments not tested

Problem:    Xxd "usage" output and other arguments not tested.
Solution:   Add a test to trigger the usage output in various ways.  Fix
            uncovered problem.

src/testdir/test_xxd.vim

@@ -20,7 +20,7 @@ endfunc
 func Test_xxd()
   call PrepareBuffer(range(1,30))
   set ff=unix
-  w XXDfile
+  w! XXDfile
 
   " Test 1: simple, filter the result through xxd
   let s:test = 1
@@ -39,15 +39,19 @@ func Test_xxd()
   exe '%!' . s:xxd_cmd . ' -r'
   call assert_equal(map(range(1,30), {v,c -> string(c)}), getline(1,'$'), s:Mess(s:test))
 
-  " Test 3: Skip the first 30 bytes
+  " Test 3: Skip the first 0x30 bytes
   let s:test += 1
-  exe '%!' . s:xxd_cmd . ' -s 0x30 %'
+  for arg in ['-s 0x30', '-s0x30', '-s+0x30', '-skip 0x030', '-seek 0x30', '-seek +0x30 --']
+    exe '%!' . s:xxd_cmd . ' ' . arg . ' %'
     call assert_equal(expected[3:], getline(1,'$'), s:Mess(s:test))
+  endfor
 
   " Test 4: Skip the first 30 bytes
   let s:test += 1
-  exe '%!' . s:xxd_cmd . ' -s -0x31 %'
+  for arg in ['-s -0x31', '-s-0x31']
+    exe '%!' . s:xxd_cmd . ' ' . arg . ' %'
     call assert_equal(expected[2:], getline(1,'$'), s:Mess(s:test))
+  endfor
 
   " Test 5: Print 120 bytes as continuous hexdump with 20 octets per line
   let s:test += 1
@@ -69,10 +73,12 @@ func Test_xxd()
 
   " Test 6: Print the date from xxd.1
   let s:test += 1
+  for arg in ['-l 13', '-l13', '-len 13']
     %d
-  exe '0r! ' . s:xxd_cmd . ' -s 0x36 -l 13 -c 13 ' . fname
+    exe '0r! ' . s:xxd_cmd . ' -s 0x36 -l 13 -cols 13 ' . fname
     $d
     call assert_equal('00000036: 3231 7374 204d 6179 2031 3939 36  21st May 1996', getline(1), s:Mess(s:test))
+  endfor
 
   " Test 7: Print C include
   let s:test += 1
@@ -87,14 +93,16 @@ func Test_xxd()
 
   " Test 8: Print C include capitalized
   let s:test += 1
+  for arg in ['-C', '-capitalize']
     call writefile(['TESTabcd09'], 'XXDfile')
     %d
-  exe '0r! ' . s:xxd_cmd . ' -i -C XXDfile'
+    exe '0r! ' . s:xxd_cmd . ' -i ' . arg . ' XXDfile'
     $d
     let expected = ['unsigned char XXDFILE[] = {',
 	  \ '  0x54, 0x45, 0x53, 0x54, 0x61, 0x62, 0x63, 0x64, 0x30, 0x39, 0x0a', '};',
 	  \ 'unsigned int XXDFILE_LEN = 11;']
     call assert_equal(expected, getline(1,'$'), s:Mess(s:test))
+  endfor
 
   " Test 9: Create a file with containing a single 'A'
   let s:test += 1
@@ -110,6 +118,39 @@ func Test_xxd()
   call PrepareBuffer(readfile('XXDfile')[0])
   call assert_equal('A', getline(1), s:Mess(s:test))
   call delete('XXDfile')
+
+  " Test 10: group with 4 octets
+  let s:test += 1
+  for arg in ['-g 4', '-group 4', '-g4']
+    call writefile(['TESTabcd09'], 'XXDfile')
+    %d
+    exe '0r! ' . s:xxd_cmd . ' ' . arg . ' XXDfile'
+    $d
+    let expected = ['00000000: 54455354 61626364 30390a             TESTabcd09.']
+    call assert_equal(expected, getline(1,'$'), s:Mess(s:test))
+    call delete('XXDfile')
+  endfor
+
+  " TODO:
+  " -o -offset
+
   %d
   bw!
 endfunc
+
+" Various ways with wrong arguments that trigger the usage output.
+func Test_xxd_usage()
+  for arg in ['-c', '-g', '-o', '-s', '-l', '-X', 'one two three']
+    new
+    exe 'r! ' . s:xxd_cmd . ' ' . arg
+    call assert_match("Usage:", join(getline(1, 3)))
+    bwipe!
+  endfor
+endfunc
+
+func Test_xxd_version()
+  new
+  exe 'r! ' . s:xxd_cmd . ' -v'
+  call assert_match("xxd V1.10 .* by Juergen Weigert", join(getline(1, 3)))
+  bwipe!
+endfunc

src/version.c

@@ -787,6 +787,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    821,
 /**/
     820,
 /**/

src/xxd/xxd.c

@@ -508,10 +508,10 @@ main(int argc, char *argv[])
 	}
       else if (!STRNCMP(pp, "-c", 2))
 	{
-	  if (pp[2] && STRNCMP("ols", pp + 2, 3))
+	  if (pp[2] && !STRNCMP("apitalize", pp + 2, 9))
-	    cols = (int)strtol(pp + 2, NULL, 0);
-	  else if (pp[2] && STRNCMP("apitalize", pp + 2, 9))
 	    capitalize = 1;
+	  else if (pp[2] && STRNCMP("ols", pp + 2, 3))
+	    cols = (int)strtol(pp + 2, NULL, 0);
 	  else
 	    {
 	      if (!argv[2])
@@ -523,7 +523,7 @@ main(int argc, char *argv[])
 	}
       else if (!STRNCMP(pp, "-g", 2))
 	{
-	  if (pp[2] && STRNCMP("group", pp + 2, 5))
+	  if (pp[2] && STRNCMP("roup", pp + 2, 4))
 	    octspergrp = (int)strtol(pp + 2, NULL, 0);
 	  else
 	    {