Re: [PATCH v2 0/3] contrib/subtree: reduce recursion during split

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 13, 2026, 23:06 UTC
Message-ID: <xmqqbjgr1g9q.fsf@gitster.g>
In-Reply-To: <xmqqldfv1gxc.fsf@gitster.g>

Junio C Hamano <gitster@pobox.com> writes:

Show 37 quoted lines

> Colin Stagner <ask+git@howdoi.land> writes:
>
>> * cs/subtree-split-recursion: when processing large history
>>   graphs on Debian or Ubuntu, "git subtree" can die with a
>>   "recursion depth reached" error. Reduce recursion.
>>
>> On Debian's POSIX sh, shell recursion is artificially limited
>> to 1000 calls. You can check if your sh has limited recursion
>> with:
>>
>>     #!/bin/sh
>>     recurse() {
>>         r=$(( r + 1 ))
>>         test "$r" -le 1000 || { echo OK; exit; }
>>         recurse
>>     } && r=0 && recurse
>>
>> Depending on the history graph, subtree split can recurse deeply
>> enough to encounter this limit. Rewrite the rejoin-deepening
>> algorithm to reduce recursive calls.
>>
>> ---
>> Changes in v2:
>> - Rebase on master
>
> We have seen two iterations of this series without anybody
> commenting on it.  Is it a sign that the topic, or possibly "git
> subtree" itself, is of interest to nobody?  Or is it that it is so
> well done that nobody had any comment on it?
>
> I don't use "git subtree" myself, and I do not know of anybody who
> will scream at me if I break it by merging an unreviewed patch, so I
> can merge it without worrying too much about fallout personally, but
> that is a tad irresponsible as the maintainer ;-)
>
> So...?  Any volunteers among those who have a higher stake in the
> program than I do (which admittedly is not a high bar to cross)?

FWIW, I can see that [1/3] is a benign clean-up that should not change any semantics. [2/3] talks about the variable $sub, which is used elsewhere, is not protected from getting overwritten by running the function inside a subprocess, but I do not know if updates to other variables (like $b, $sq, $repository, but not $fail_msg, $hint1 and $hint2 that are used only in this function) want to be seen after the calls to this function outside (and do not want to find out myself---I'd rather want to see somebody else with stakes in "git subtree" to verify), but otherwise the change looks benigh to me. I have no idea if what [3/3] does is sensible or not (and again, I'd rather want to see somebody with stakes to double check).

Thanks.