cmd: no need for pre function hook now

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

cmd.h

@@ -2,12 +2,10 @@
 #define CMD_H
 
 typedef void (*cgit_cmd_fn)(void);
-typedef void (*cgit_cmd_pre_fn)(void);
 
 struct cgit_cmd {
 	const char *name;
 	cgit_cmd_fn fn;
-	cgit_cmd_pre_fn pre;
 	unsigned int want_repo:1,
 		want_vpath:1,
 		is_clone:1;