vim-patch:8.1.1100: tag file without trailing newline no longer works

Problem:    Tag file without trailing newline no longer works. (Marco Hinz)
Solution:   Don't expect a newline at the end of the file.

fd700393be

src/nvim/tag.c

@@ -1527,9 +1527,11 @@ line_read_in:
         }
 
 parse_line:
-        if (vim_strchr(lbuf, NL) == NULL && !use_cscope) {
-          // Truncated line, ignore it. Has been reported for Mozilla JS with
-          // extremely long names.
+        // When the line is too long the NUL will not be in the
+        // last-but-one byte (see vim_fgets()).
+        // Has been reported for Mozilla JS with extremely long names.
+        // In that case we can't parse it and we ignore the line.
+        if (lbuf[LSIZE - 2] != NUL && !use_cscope) {
           if (p_verbose >= 5) {
             verbose_enter();
             MSG(_("Ignoring long line in tags file"));

src/nvim/testdir/test_taglist.vim

@@ -61,3 +61,16 @@ func Test_tags_too_long()
   call assert_fails('tag ' . repeat('x', 1020), 'E426')
   tags
 endfunc
+
+" For historical reasons we support a tags file where the last line is missing
+" the newline.
+func Test_tagsfile_without_trailing_newline()
+  call writefile(["Foo\tfoo\t1"], 'Xtags', 'b')
+  set tags=Xtags
+
+  let tl = taglist('.*')
+  call assert_equal(1, len(tl))
+  call assert_equal('Foo', tl[0].name)
+
+  call delete('Xtags')
+endfunc