Re: [PATCH] Convert "struct cache_entry *" to "const ..." wherever possible

> I attempted to make index_state->cache[] a "const struct cache_entry **"
> to find out how existing entries in index are modified and where. The
> question I have is what do we do if we really need to keep track of on-disk
> changes in the index. The result is
>
>  - diff-lib.c: setting CE_UPTODATE
>
>  - name-hash.c: setting CE_HASHED
>
>  - preload-index.c, read-cache.c, unpack-trees.c and
>    builtin/update-index: obvious
>
>  - entry.c: write_entry() may refresh the checked out entry via
>    fill_stat_cache_info(). This causes "non-const struct cache_entry
>    *" in builtin/apply.c, builtin/checkout-index.c and
>    builtin/checkout.c
>
>  - builtin/ls-files.c: --with-tree changes stagemask and may set
>    CE_UPDATE
>
> Of these, write_entry() and its call sites are probably most
> interesting because it modifies on-disk info. But this is stat info
> and can be retrieved via refresh, at least for porcelain
> commands. Other just uses ce_flags for local purposes.
>
> So, keeping track of "dirty" entries is just a matter of setting a
> flag in index modification functions exposed by read-cache.c. Except
> unpack-trees, the rest of the code base does not do anything funny
> behind read-cache's back.
>
> The actual patch is less valueable than the summary above. But if
> anyone wants to re-identify the above sites. Applying this patch, then
> this:
>
>     diff --git a/cache.h b/cache.h
>     index 430d021..1692891 100644
>     --- a/cache.h
>     +++ b/cache.h
>     @@ -267,7 +267,7 @@ static inline unsigned int canon_mode(unsigned int mode)
>      #define cache_entry_size(len) (offsetof(struct cache_entry,name) + (len) + 1)
>     
>      struct index_state {
>     -	struct cache_entry **cache;
>     +	const struct cache_entry **cache;
>      	unsigned int version;
>      	unsigned int cache_nr, cache_alloc, cache_changed;
>      	struct string_list *resolve_undo;
>
> will help quickly identify them without bogus warnings.