Extract shell_count_argc from mch_call_shell

src/os/shell.c

@@ -2,12 +2,14 @@
 
 #include "os/shell.h"
 #include "types.h"
+#include "vim.h"
 #include "ascii.h"
+#include "charset.h"
 
 
-void shell_skip_word(char_u **ptr)
+void shell_skip_word(char_u **cmd)
 {
-  char_u *p = *ptr;
+  char_u *p = *cmd;
   bool inquote = false;
 
   // Move `p` to the end of shell word by advancing the pointer it while it's
@@ -19,5 +21,35 @@ void shell_skip_word(char_u **ptr)
     ++p;
   }
 
-  *ptr = p;
+  *cmd = p;
+}
+
+int shell_count_argc(char_u **ptr)
+{
+  int rv = 0;
+  char_u *p = *ptr;
+
+  while (true) {
+    rv++;
+    shell_skip_word(&p);
+    if (*p == NUL)
+      break;
+    // Move to the next word
+    p = skipwhite(p);
+  }
+
+  // Account for multiple args in p_shcf('shellcmdflag' option)
+  p = p_shcf;
+  while (true) {
+    // Same as above, but doesn't need to take quotes into consideration
+    p = skiptowhite(p);
+    if (*p == NUL)
+      break;
+    rv++;
+    p = skipwhite(p);
+  }
+
+  *ptr = p;
+
+  return rv;
 }