add-patch: add diff.context command line overrides

This patch compliments the previous commit, where builtins that use
add-patch infrastructure now respect diff.context and
diff.interHunkContext file configurations.

In particular, this patch helps users who don't want to set persistent
context configurations or just want a way to override them on a one-time
basis, by allowing the relevant builtins to accept corresponding command
line options that override the file configurations.

This mimics commands such as diff and log, which allow for both context
file configuration and command line overrides.

Signed-off-by: Leon Michalak <leonmichalak6@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

commit.h

@@ -2,6 +2,7 @@
 #define COMMIT_H
 
 #include "object.h"
+#include "add-interactive.h"
 
 struct signature_check;
 struct strbuf;
@@ -257,7 +258,7 @@ int for_each_commit_graft(each_commit_graft_fn, void *);
 int interactive_add(struct repository *repo,
 		    const char **argv,
 		    const char *prefix,
-		    int patch);
+		    int patch, struct add_p_opt *add_p_opt);
 
 struct commit_extra_header {
 	struct commit_extra_header *next;