From mboxrd@z Thu Jan  1 00:00:00 1970
From: Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH 3/3] pretty=format: Avoid some expensive calculations when not needed
Date: Mon, 05 Nov 2007 11:51:15 -0800
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To: Johannes Schindelin <Johannes.Schindelin@gmx.de>
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In-Reply-To: <Pine.LNX.4.64.0711041915290.4362@racer.site> (Johannes
	Schindelin's message of "Sun, 4 Nov 2007 19:15:44 +0000 (GMT)")
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Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> Unfortunately, we cannot reuse the result of that function, which
> would be cleaner: there are more users than just git log.  Most
> notably, git-archive with "$Format:...$" substitution.

That makes sense.


> diff --git a/pretty.c b/pretty.c
> index 490cede..241e91c 100644
> --- a/pretty.c
> +++ b/pretty.c
> @@ -393,6 +393,7 @@ void format_commit_message(const struct commit *commit,
>  	int i;
>  	enum { HEADER, SUBJECT, BODY } state;
>  	const char *msg = commit->buffer;
> +	char *active = interp_find_active(format, table, ARRAY_SIZE(table));
> ...
> +	if (active[IHASH])
> +		interp_set_entry(table, IHASH,
> +				sha1_to_hex(commit->object.sha1));
> +	if (active[IHASH_ABBREV])
> +		interp_set_entry(table, IHASH_ABBREV,
>  			find_unique_abbrev(commit->object.sha1,
>  				DEFAULT_ABBREV));

Instead of allocating a separate array and freeing at the end,
wouldn't it make more sense to have a bitfield that records what
is used by the format string inside the array elements?