This makes three functions and associated option structures from
builtin-grep available from other parts of the system.
* options to drive built-in grep engine is stored in struct
grep_opt;
* pattern strings and extended grep expressions are added to
struct grep_opt with append_grep_pattern();
* when finished calling append_grep_pattern(), call
compile_grep_patterns() to prepare for execution;
* call grep_buffer() to find matches in the in-core buffer.
This also adds an internal option "status_only" to grep_opt,
which suppresses any output from grep_buffer(). Callers of the
function as library can use it to check if there is a match
without producing any output.
Signed-off-by: Junio C Hamano <junkio@cox.net>
