vim-patch:8.0.0446: the ";" command does not work after some characters

Problem:    The ";" command does not work after characters with a lower byte
            that is NUL.
Solution:   Properly check for not having a previous character. (Hirohito
            Higashi)

454709baff

src/nvim/search.c

@@ -1380,13 +1380,15 @@ int searchc(cmdarg_T *cap, int t_cmd)
           lastc_bytelen += (*mb_char2bytes)(cap->ncharC2, lastc_bytes + lastc_bytelen);
       }
     }
-  } else {            /* repeat previous search */
+  } else {            // repeat previous search
-    if (*lastc == NUL)
+    if (*lastc == NUL && lastc_bytelen == 1) {
       return FAIL;
-    if (dir)            /* repeat in opposite direction */
+    }
+    if (dir) {        // repeat in opposite direction
       dir = -lastcdir;
-    else
+    } else {
       dir = lastcdir;
+    }
     t_cmd = last_t_cmd;
     c = *lastc;
     /* For multi-byte re-use last lastc_bytes[] and lastc_bytelen. */

src/nvim/testdir/test_alot_utf8.vim

@@ -5,6 +5,7 @@
 " runtest.vim.  Checking for the multi_byte feature is in the individual
 " files, so that they can be run by themselves.
 
+source test_charsearch_utf8.vim
 source test_expr_utf8.vim
 source test_matchadd_conceal_utf8.vim
 source test_regexp_utf8.vim

src/nvim/testdir/test_charsearch_utf8.vim

@@ -0,0 +1,44 @@
+" Tests for related f{char} and t{char} using utf-8.
+if !has('multi_byte')
+  finish
+endif
+
+" Test for t,f,F,T movement commands
+function! Test_search_cmds()
+  new!
+  call setline(1, "・最初から最後まで最強のVimは最高")
+  1
+  normal! f最
+  call assert_equal([0, 1, 4, 0], getpos('.'))
+  normal! ;
+  call assert_equal([0, 1, 16, 0], getpos('.'))
+  normal! 2;
+  call assert_equal([0, 1, 43, 0], getpos('.'))
+  normal! ,
+  call assert_equal([0, 1, 28, 0], getpos('.'))
+  bw!
+endfunction
+
+" vim: shiftwidth=2 sts=2 expandtab
+" Tests for related f{char} and t{char} using utf-8.
+if !has('multi_byte')
+  finish
+endif
+
+" Test for t,f,F,T movement commands
+function! Test_search_cmds()
+  new!
+  call setline(1, "・最初から最後まで最強のVimは最高")
+  1
+  normal! f最
+  call assert_equal([0, 1, 4, 0], getpos('.'))
+  normal! ;
+  call assert_equal([0, 1, 16, 0], getpos('.'))
+  normal! 2;
+  call assert_equal([0, 1, 43, 0], getpos('.'))
+  normal! ,
+  call assert_equal([0, 1, 28, 0], getpos('.'))
+  bw!
+endfunction
+
+" vim: shiftwidth=2 sts=2 expandtab