argv_array: offer to split a string by whitespace

This is a simple function that will interpret a string as a whitespace
delimited list of values, and add those values into the array.

Note: this function does not (yet) offer to split by arbitrary delimiters,
or keep empty values in case of runs of whitespace, or de-quote Unix shell
style. All fo this functionality can be added later, when and if needed.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/argv-array.h b/argv-array.h
index 29056e4..750c30d 100644
--- a/argv-array.h
+++ b/argv-array.h
@@ -19,6 +19,8 @@ LAST_ARG_MUST_BE_NULL
 void argv_array_pushl(struct argv_array *, ...);
 void argv_array_pushv(struct argv_array *, const char **);
 void argv_array_pop(struct argv_array *);
+/* Splits by whitespace; does not handle quoted arguments! */
+void argv_array_split(struct argv_array *, const char *);
 void argv_array_clear(struct argv_array *);
 const char **argv_array_detach(struct argv_array *);