fast-rebase: change assert() to BUG()

assert() can succinctly document expectations for the code, and do so in
a way that may be useful to future folks trying to refactor the code and
change basic assumptions; it allows them to more quickly find some
places where their violations of previous assumptions trips things up.

Unfortunately, assert() can surround a function call with important
side-effects, which is a huge mistake since some users will compile with
assertions disabled.  I've had to debug such mistakes before in other
codebases, so I should know better.  Luckily, this was only in test
code, but it's still very embarrassing.  Change an assert() to an if
(...) BUG (...).

Signed-off-by: Elijah Newren <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: newren

t/helper/test-fast-rebase.c

@@ -124,7 +124,8 @@ int cmd__fast_rebase(int argc, const char **argv)
 	assert(oideq(&onto->object.oid, &head));
 
 	hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
-	assert(repo_read_index(the_repository) >= 0);
+	if (repo_read_index(the_repository) < 0)
+		BUG("Could not read index");
 
 	repo_init_revisions(the_repository, &revs, NULL);
 	revs.verbose_header = 1;