Re: [PATCH v3] fetch: optionally allow disabling FETCH_HEAD update

From: Derrick Stolee <stolee@gmail.com>
To: Junio C Hamano <gitster@pobox.com>, Jonathan Nieder <jrnieder@gmail.com>
Cc: Junio C Hamano via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org, Derrick Stolee <derrickstolee@github.com>,
	Emily Shaffer <emilyshaffer@google.com>
Subject: Re: [PATCH v3] fetch: optionally allow disabling FETCH_HEAD update
Date: Thu, 13 Aug 2020 21:13:14 -0400	[thread overview]
Message-ID: <8acc67e5-4b17-7fdc-0685-b5113e819010@gmail.com> (raw)
In-Reply-To: <xmqqh7t740vu.fsf_-_@gitster.c.googlers.com>

On 8/13/2020 12:37 AM, Junio C Hamano wrote:
> If you run fetch but record the result in remote-tracking branches,
> and either if you do nothing with the fetched refs (e.g. you are
> merely mirroring) or if you always work from the remote-tracking
> refs (e.g. you fetch and then merge origin/branchname separately),
> you can get away with having no FETCH_HEAD at all.
> 
> Teach "git fetch" a command line option "--[no-]write-fetch-head".
> The default is to write FETCH_HEAD, and the option is primarily
> meant to be used with the "--no-" prefix to override this default,
> because there is no matching fetch.writeFetchHEAD configuration
> variable to flip the default to off (in which case, the positive
> form may become necessary to defeat it).
> 
> Note that under "--dry-run" mode, FETCH_HEAD is never written;
> otherwise you'd see list of objects in the file that you do not
> actually have.  Passing `--write-fetch-head` does not force `git
> fetch` to write the file.
> 
> Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
> 
>  * So, it becomes much smaller by punting the whole configuration
>    thing, as we do not need the extra code for config parsing and
>    there is no need for code to override the user configuration when
>    driving "git fetch" from "git pull".

Sounds good. I'll incorporate this patch into my next version,
except it seems you dropped this test:

diff --git a/t/t5521-pull-options.sh b/t/t5521-pull-options.sh
index 159afa7ac8..db1a381cd9 100755
--- a/t/t5521-pull-options.sh
+++ b/t/t5521-pull-options.sh
@@ -85,6 +85,13 @@ test_expect_success 'git pull --cleanup errors early on invalid argument' '
        test -s err)
 '
 
+test_expect_success 'git pull --no-write-fetch-head fails' '
+       mkdir clonedwfh &&
+       (cd clonedwfh && git init &&
+       test_expect_code 129 git pull --no-write-fetch-head "../parent" >out 2>err &&
+       test_must_be_empty out &&
+       test_i18ngrep "no-write-fetch-head" err)
+'
 
 test_expect_success 'git pull --force' '
        mkdir clonedoldstyle &&

which I changed "test_must_fail" to "test_expect_code 129" to
demonstrate that this is a usage error, not just any error.

Thanks,
-Stolee
