checkout.c: enable fscache for checkout_entry

This is to speed up git checkout for directory in very large repositories.

Taking file stats while directory traversing is faster than
stating to each files on windows.

`git checkout .` in master branch of chromium repositry, having 284659 files,
takes more than 18 seconds.
This patch improved the time to around 4 seconds on my SSD laptop.

Signed-off-by: Takuto Ikuta <[email protected]>

Author: Takuto Ikuta

builtin/checkout.c

@@ -359,6 +359,7 @@ static int checkout_paths(const struct checkout_opts *opts,
 	state.istate = &the_index;
 
 	enable_delayed_checkout(&state);
+	enable_fscache(1);
 	for (pos = 0; pos < active_nr; pos++) {
 		struct cache_entry *ce = active_cache[pos];
 		if (ce->ce_flags & CE_MATCHED) {
@@ -373,6 +374,7 @@ static int checkout_paths(const struct checkout_opts *opts,
 			pos = skip_same_name(ce, pos) - 1;
 		}
 	}
+	enable_fscache(0);
 	errs |= finish_delayed_checkout(&state);
 
 	if (write_locked_index(&the_index, &lock_file, COMMIT_LOCK))