Subject: Re: [RFC] git checkout $tree -- $path always rewrites files

From: Junio C Hamano <[email-masked]>
Date: Thu, 13 Nov 2014 13:18:43 -0800

Jeff King <[email-masked]> writes:

> On Thu, Nov 13, 2014 at 02:26:55PM -0500, Jeff King wrote:
>
>> > Makes sense, including the use of strbuf (otherwise you would
>> > allocate ce and then discard when it turns out that it is not
>> > needed, which is probably with the same allocation pressure, but
>> > looks uglier).
>> 
>> Exactly. Constructing it in ce->name does save you an allocation/memcpy
>> in the case that we actually use the new entry, but I thought it would
>> look weirder. It probably doesn't matter much either way, so I tried to
>> write the most obvious thing.
>
> Actually, it is not that bad:

Yeah, actually it does look better; want me to squash it into the
patch before queuing?

>
> diff --git a/builtin/checkout.c b/builtin/checkout.c
> index 5410dac..5a78758 100644
> --- a/builtin/checkout.c
> +++ b/builtin/checkout.c
> @@ -67,6 +67,7 @@ static int update_some(const unsigned char *sha1, const char *base, int baselen,
>  {
>  	int len;
>  	struct cache_entry *ce;
> +	int pos;
>  
>  	if (S_ISDIR(mode))
>  		return READ_TREE_RECURSIVE;
> @@ -79,6 +80,23 @@ static int update_some(const unsigned char *sha1, const char *base, int baselen,
>  	ce->ce_flags = create_ce_flags(0) | CE_UPDATE;
>  	ce->ce_namelen = len;
>  	ce->ce_mode = create_ce_mode(mode);
> +
> +	/*
> +	 * If the entry is the same as the current index, we can leave the old
> +	 * entry in place. Whether it is UPTODATE or not, checkout_entry will
> +	 * do the right thing.
> +	 */
> +	pos = cache_name_pos(ce->name, ce->ce_namelen);
> +	if (pos >= 0) {
> +		struct cache_entry *old = active_cache[pos];
> +		if (ce->ce_mode == old->ce_mode &&
> +		    !hashcmp(ce->sha1, old->sha1)) {
> +			old->ce_flags |= CE_UPDATE;
> +			free(ce);
> +			return 0;
> +		}
> +	}
> +
>  	add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
>  	return 0;
>  }
>
> and in some ways more readable, as you form the whole thing, and then as
> the final step either add it, or realize that what is there is fine (I'd
> almost wonder if it could be a flag to add_cache_entry).
>
> -Peff