Re: [RFC PATCH] rerere: fix overeager gc

From: Junio C Hamano <gitster@pobox.com>
Date: Jun 29, 2010, 17:59 UTC
Message-ID: <7vy6dx90uk.fsf@alter.siamese.dyndns.org>
In-Reply-To: <1277811498-17288-1-git-send-email-szeder@ira.uka.de>

SZEDER Gábor <szeder@ira.uka.de> writes:

> ...  But I'm not sure I
> can rely on that when gc'ing.

Looking at the timestamp of "thisimage" would probaboly be more sensible than "preimage" alone, _if_ "thisimage" still exists. It is rewritten every time this particular conflict is observed; this is not necessarily when the recorded resolution is _used_, but it may be close enough in practice.

You probably would want to rename the helper as "last_checked_at", though.

After rerere does its work, however, "thisimage" does not have to stay around (the user can remove it, or we could enhance "gc" to do so).

> +		if (has_rerere_resolution(e->d_name)) {
> +			then = rerere_last_used_at(e->d_name);
> +			if (!then)
> +				continue;

Here you already know that you have resolution (i.e. "postimage"), but your new function cannot stat a corresponding "thisimage", so you err on the safer side---but that means you may keep pre/post image pairs forever if somebody removes otherwise unused "thisimage" from a distant past. Perhaps we should apply cutoff_noresolve to the entry here?

One possibility is to look at the timestamp of the directory itself instead. Then we can safely gc otherwise-unused "thisimage" file when rerere is not in use. I wonder if directory m_time timestamps are usable for this purpose on non-POSIX platforms?