Re: [PATCH v11 06/10] convert: add 'working-tree-encoding' attribute

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 9, 2018, 19:10 UTC
Message-ID: <xmqqmuzh5alb.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <20180309173536.62012-7-lars.schneider@autodesk.com>

lars.schneider@autodesk.com writes:

Show 14 quoted lines

> +static const char *default_encoding = "UTF-8";
> +
> ...
> +static const char *git_path_check_encoding(struct attr_check_item *check)
> +{
> +	const char *value = check->value;
> +
> +	if (ATTR_UNSET(value) || !strlen(value))
> +		return NULL;
> +
> +	if (ATTR_TRUE(value) || ATTR_FALSE(value)) {
> +		error(_("working-tree-encoding attribute requires a value"));
> +		return NULL;
> +	}

Hmph, so we decide to be loud but otherwise ignore an undefined configuration? Shouldn't we rather die instead to avoid touching the user data in unexpected ways?

> +
> +	/* Don't encode to the default encoding */
> +	if (!strcasecmp(value, default_encoding))
> +		return NULL;

Is this an optimization to avoid "recode one encoding to the same encoding" no-op overhead? We already have the optimization in the same spirit in may existing codepaths that has nothing to do with w-t-e, and I think we should share the code. Two pieces of thought comes to mind.

One is a lot smaller in scale: Is same_encoding() sufficient for this callsite instead of strcasecmp()?

The other one is a lot bigger: Looking at all the existing callers of same_encoding() that call reencode_string() when it returns false, would it make sense to drop same_encoding() and move the optimization to reencode_string() instead?

I suspect that the answer to the smaller one is "yes, and even if not, it should be easy to enhance/extend same_encoding() to make it do what we want it to, and such a change will benefit even existing callers." The answer to the larger one is likely "the optimization is not about skipping only reencode_string() call but other things are subtly different among callers of same_encoding(), so such a refactoring would not be all that useful."

The above still holds for the code after 10/10 touches this part.