[PATCH] revision.c: Remove unneeded check for NULL

The function is called only from one place, which makes sure to have `interesting_cache` not NULL. Additionally it is a dereferenced a few lines before unconditionally, which would result in a segmentation fault.

Signed-off-by: Stefan Beller <sbeller@google.com>
---

Notes:
    > So I think the right solution is just to drop the conditional entirely.
    > The current code is not wrong (it is always a noop). What you have here
    > actually misbehaves; it does not update the cache slot when it has
    > become UNINTERESTING. That does not produce wrong results, but it loses
    > the benefit of the cache in some cases.
    
    After reading the code a bit more, I agree.
    
    > I'm having trouble parsing this sentence.  Do you mean that limit_list()
    > only calls still_interesting() (and thus, indirectly,
    > everybody_uninteresting()), with the second parameter equal to the
    > address of the local interesting_cache variable, so it can never be
    > NULL?
    
    I completely reworded the commit message.
    
    > Should there be
    >
    >        if (!interesting_cache)
    >                die("BUG: &interesting_cache == NULL");
    >
    > checks at the top of still_interesting and everybody_uninteresting to
    > futureproof this?
    
    I don't think this is necessary as these functions are local functions
    so when somebody wants to use them they will be aware of the limitations.
    
    > This code seems to be underdocumented.
    
    I am not a expert in this area of the code, so I hoped Peff
    would document it if he feels like so.

 revision.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)