patch 8.0.1793: no test for "vim -g"

Problem:    No test for "vim -g".
Solution:   Add a test for "-g" and "-y".

src/testdir/shared.vim

@@ -227,6 +227,8 @@ func GetVimProg()
   return readfile('vimcmd')[0]
 endfunc
 
+let g:valgrind_cnt = 1
+
 " Get the command to run Vim, with -u NONE and --not-a-term arguments.
 " If there is an argument use it instead of "NONE".
 func GetVimCommand(...)
@@ -244,14 +246,26 @@ func GetVimCommand(...)
   " For Unix Makefile writes the command to use in the second line of the
   " "vimcmd" file, including environment options.
   " Other Makefiles just write the executable in the first line, so fall back
-  " to that if there is no second line.
-  let cmd = get(lines, 1, lines[0])
+  " to that if there is no second line or it is empty.
+  if len(lines) > 1 && lines[1] != ''
+    let cmd = lines[1]
+  else
+    let cmd = lines[0]
+  endif
+
   let cmd = substitute(cmd, '-u \f\+', '-u ' . name, '')
   if cmd !~ '-u '. name
     let cmd = cmd . ' -u ' . name
   endif
   let cmd .= ' --not-a-term'
   let cmd = substitute(cmd, 'VIMRUNTIME=.*VIMRUNTIME;', '', '')
+
+  " If using valgrind, make sure every run uses a different log file.
+  if cmd =~ 'valgrind.*--log-file='
+    let cmd = substitute(cmd, '--log-file=\(^\s*\)', '--log-file=\1.' . g:valgrind_cnt, '')
+    let g:valgrind_cnt += 1
+  endif
+
   return cmd
 endfunc
 
@@ -274,9 +288,6 @@ endfunc
 
 func RunVimPiped(before, after, arguments, pipecmd)
   let cmd = GetVimCommand()
-  if cmd == ''
-    return 0
-  endif
   let args = ''
   if len(a:before) > 0
     call writefile(a:before, 'Xbefore.vim')