Re: Re: [PATCH] builtin/clone.c: add --no-shallow option

From: lilinchao@oschina.cn <lilinchao@oschina.cn>
Date: Feb 4, 2021, 10:32 UTC
Message-ID: <57d5526c66d411eb81800024e87935e7@oschina.cn>
In-Reply-To: <xmqq35yc9yan.fsf@gitster.c.googlers.com>

-------------- lilinchao@oschina.cn

Show 8 quoted lines

>"Li Linchao via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
>> From: lilinchao <lilinchao@oschina.cn>
>>
>> This patch add a new option that reject to clone a shallow repository.
>
>A canonical form of our log message starts by explaining the need,
>and then presents the solution at the end.

Ok, will do.

Show 6 quoted lines

>
>> Clients don't know it's a shallow repository until they download it
>> locally, in some scenariors, clients just don't want to clone this kind
>
>"scenarios".  "in some scenarios" would have to be clarified a bit
>more to justify why it is a good idea to have such a feature.

I found an issue described like this:

    The blame information can be completely wrong when fetching it from
    a shallow clone, without errors or warnings. When the outcome is invalid
    data, it's extremely difficult to diagnose that it comes from a shallow clone.
    If a line in a file was not changed in the commits that were downloaded as
    part of the shallow fetch, git will report the first known commit as the author.
    This has a big impact on the auto-assignment of new issues.

It looks like this is another scenario that can prove this feature is necessary.

Show 19 quoted lines

>
>> of repository, and want to exit the process immediately without creating
>> any unnecessary files.
>
>"clients don't know it's a shallow repository until they download"
>leading to "so let's reject immediately upon finding out that they
>are shallow" does make sense as a flow of thought, though.
>
>> +--no-shallow::
>> +	Don't clone a shallow source repository. In some scenariors, clients
>
>"scenarios" (no 'r').
>
>> diff --git a/builtin/clone.c b/builtin/clone.c
>> old mode 100644
>> new mode 100755
>
>Unwarranted "chmod +x"; accidents do happen, but please be careful
>before making what you did public ;-)

Oops, this happened when I edited it in VS Code, it noticed me 'permission denied' when I want to save the file.

Show 35 quoted lines

>
>> @@ -90,6 +91,7 @@ static struct option builtin_clone_options[] = {
>>  OPT__VERBOSITY(&option_verbosity),
>>  OPT_BOOL(0, "progress", &option_progress,
>>  N_("force progress reporting")),
>> +	OPT_BOOL(0, "no-shallow", &option_no_shallow, N_("don't clone shallow repository")),
>>  OPT_BOOL('n', "no-checkout", &option_no_checkout,
>>  N_("don't create a checkout")),
>>  OPT_BOOL(0, "bare", &option_bare, N_("create a bare repository")),
>
>It is a bad idea to give a name that begins with "no-" to an option
>whose default can be tweaked by a configuration variable [*].  If
>the configuration is named "rejectshallow", perhaps it is better to
>call it "--reject-shallow" instead. 
>
>This is because configured default must be overridable from the
>command line.  I.e. even if you have in your ~/.gitconfig this:
>
>    [clone]
>        rejectshallow = true
>
>you should be able to say "allow it only this time", with
>
> $ git clone --no-reject-shallow http://github.com/git/git/ git
>
>and you do not want to have to say "--no-no-shallow", which sounds
>just silly.
>
>	Side note. it is a bad idea in general, even if the option
>	does not have corresponding configuration variable.  The
>	existing "no-checkout" is a historical accident that
>	happened long time ago and cannot be removed due to
>	compatibility.  Let's not introduce a new option that
>	follows such a bad pattern. 
>

You're right, "--reject-shallow" is much better. I didn't realize that bool options have default [no-] option.

Show 38 quoted lines

>> @@ -963,6 +968,7 @@ static int path_exists(const char *path)
>>  int cmd_clone(int argc, const char **argv, const char *prefix)
>>  {
>>  int is_bundle = 0, is_local;
>> +	int is_shallow = 0;
>>  const char *repo_name, *repo, *work_tree, *git_dir;
>>  char *path, *dir, *display_repo = NULL;
>>  int dest_exists, real_dest_exists = 0;
>> @@ -1215,6 +1221,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
>>  if (filter_options.choice)
>>  warning(_("--filter is ignored in local clones; use file:// instead."));
>>  if (!access(mkpath("%s/shallow", path), F_OK)) {
>> +	is_shallow = 1;
>>  if (option_local > 0)
>>  warning(_("source repository is shallow, ignoring --local"));
>>  is_local = 0;
>
>This change is to the local clone codepath.  Cloning over the wire
>would not go through this part.  And throughout the patch, this is
>the only place that sets is_shallow to 1.
>
>Also let's note that this is after we called parse_options(), so the
>value of option_no_shallow is known at this point.
>
>So, this patch does not even *need* to introduce a new "is_shallow"
>variable at all.  It only needs to add
>
>                        if (option_no_shallow)
>                                die(...);
>
>instead of adding "is_shallow = 1" to the above hunk.
>
>I somehow think that this is only half a feature---wouldn't it be
>more useful if we also rejected a non-local clone from a shallow
>repository? 
>
>And for that ...
>

  
After I applied your review suggestions above, then we can reject a 
non-local clone from shallow repo. For now, it will clone a empty 
repo with --no-local option.

Show 73 quoted lines

>
>> diff --git a/t/t5606-clone-options.sh b/t/t5606-clone-options.sh
>> index 7f082fb23b6a..9d310dbb158a 100755
>> --- a/t/t5606-clone-options.sh
>> +++ b/t/t5606-clone-options.sh
>> @@ -42,6 +42,13 @@ test_expect_success 'disallows --bare with --separate-git-dir' '
>> 
>>  '
>> 
>> +test_expect_success 'reject clone shallow repository' '
>> +	git clone --depth=1 --no-local parent shallow-repo &&
>> +	test_must_fail git clone --no-shallow shallow-repo out 2>err &&
>> +	test_i18ngrep -e "source repository is shallow, reject to clone." err
>> +
>> +'
>> +
>
>... in addition to the test for a local clone above, you'd also want
>to test a non-local clone, perhaps like so:
>
>test_expect_success 'reject clone shallow repository' '
>	rm -fr shallow-repo &&
>	git clone --depth=1 --no-local parent shallow-repo &&
>	test_must_fail git clone --no-shallow --no-local shallow-repo out 2>err &&
>	test_i18ngrep -e "source repository is shallow, reject to clone." err
>
>' 
>
>Ditto for the other test script.
>
>Also, you would want to make sure that the command line overrides
>the configured default.  I.e.
>
>	git -c clone.rejectshallow=false clone --reject-shallow
>
>should refuse to clone from a shallow one, while there should be a
>way to countermand a configured "I always refuse to clone from a
>shallow repository" with "but let's allow it only this time", i.e.
>
>	git -c clone.rejectshallow=true clone --no-reject-shallow
>
>or something along the line.
>
>
>> diff --git a/t/t5611-clone-config.sh b/t/t5611-clone-config.sh
>> index 8e0fd398236b..3aab86ad4def 100755
>> --- a/t/t5611-clone-config.sh
>> +++ b/t/t5611-clone-config.sh
>> @@ -92,6 +92,13 @@ test_expect_success 'clone -c remote.<remote>.fetch=<refspec> --origin=<name>' '
>>  test_cmp expect actual
>>  '
>> 
>> +test_expect_success 'clone -c clone.rejectshallow' '
>> +	rm -rf child &&
>> +	git clone --depth=1 --no-local . child &&
>> +	test_must_fail git clone -c clone.rejectshallow child out 2>err &&
>
>This is not quite right, even though it may happen to work.  The
>"clone.rejectshallow" variable is a configuration about what should
>happen when creating a new repository by cloning, so letting "git
>clone -c var[=val]" to set the variable _in_ the resulting repository
>would not make much sense.  Even if the clone succeeded, nobody would
>look at that particular configuration variable that is set in the
>resulting repository.
>
>I think it would communicate to the readers better what we are
>trying to do, if we write
>
>	test_must_fail git -c clone.rejectshallow=true clone child out
>
>instead.
> 
>Thanks.

Thank you for so many effective suggestions, I will write test case more carefully :)