From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS3215 2.6.0.0/16 X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from out1.vger.email (out1.vger.email [IPv6:2620:137:e000::1:20]) by dcvr.yhbt.net (Postfix) with ESMTP id 9E9F31F8C4 for ; Wed, 23 Mar 2022 15:19:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232881AbiCWPUk (ORCPT ); Wed, 23 Mar 2022 11:20:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33914 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229765AbiCWPUi (ORCPT ); Wed, 23 Mar 2022 11:20:38 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 690E3554BB for ; Wed, 23 Mar 2022 08:19:08 -0700 (PDT) Received: from fraeml706-chm.china.huawei.com (unknown [172.18.147.206]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4KNsQV5PSfz689QQ for ; Wed, 23 Mar 2022 23:16:50 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml706-chm.china.huawei.com (10.206.15.55) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2375.24; Wed, 23 Mar 2022 16:19:04 +0100 Received: from [10.47.85.68] (10.47.85.68) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Wed, 23 Mar 2022 15:19:04 +0000 Message-ID: <6fa76f28-063b-8964-c0a2-642dae88f1b3@huawei.com> Date: Wed, 23 Mar 2022 15:19:06 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 To: From: John Garry Subject: [Question] .git folder file updates for changing head commit Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.47.85.68] X-ClientProxiedBy: lhreml730-chm.china.huawei.com (10.201.108.81) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Hi guys, I have a question about which files in the .git folder are updated as we change the head commit. I could check the codebase myself but prob will make a mistake and maybe some expert would be so kind as to just kindly tell me. For building the linux perf tool we use the git head commit id as part of the tool version sting. To save time in re-building, the Makefile rule has a dependency on .git/HEAD for rebuilding. An alternative approach would be to compare git log output to check current versus previous build head commit, but that is seen as inefficient time-wise. The problem is that actions like git cherry-pick and git reset --hard HEAD^ may not update .git/HEAD (so don't trigger a rebuild). Is there some more suitable file(s) which we could use as a dependency? From my limited experimentation, .git/index seems to always update when the changing head commit. Thanks, john