Re: [PATCH v4 1/4] sparse index: enable only for git repos

> On Mon, Nov 22, 2021 at 2:42 PM Lessley Dennington via GitGitGadget
> <gitgitgadget@gmail.com> wrote:
>>
>> From: Lessley Dennington <lessleydennington@gmail.com>
>>
>> Check whether git dir exists before adding any repo settings. If it
>> does not exist, BUG with the message that one cannot add settings for an
>> uninitialized repository. If it does exist, proceed with adding repo
>> settings.
>>
>> Additionally, ensure the above BUG is not triggered when users pass the -h
>> flag by adding a check for the repository to the checkout and pack-objects
>> builtins.
> 
> Why only checkout and pack-objects?  Why don't the -h flags to all of
> the following need it as well?:
> 
> $ git grep -l prepare_repo_settings | grep builtin/
> builtin/add.c
> builtin/blame.c
> builtin/checkout.c
> builtin/commit.c
> builtin/diff.c
> builtin/fetch.c
> builtin/gc.c
> builtin/merge.c
> builtin/pack-objects.c
> builtin/rebase.c
> builtin/reset.c
> builtin/revert.c
> builtin/sparse-checkout.c
> builtin/update-index.c
> 
> If none of these need it, was it because they put
> prepare_repo_settings() calls after some other basic checks had been
> done so more do not have to be added?  If so, is there a similar place
> in checkout and pack-objects where their calls to
> prepare_repo_settings() can be moved?  (Looking ahead, it appears you
> moved some code in patch 2 to do something like this.  Are the similar
> moves that could be done here?)
> 

>> Finally, ensure the above BUG is not triggered for commit-graph by
>> returning early if the git directory does not exist.
> 
> If commit-graph needs a special case to avoid triggering the BUG,
> wouldn't several of these need it too?:
> 
> $ git grep -l prepare_repo_settings | grep -v builtin/
> commit-graph.c
> fetch-negotiator.c
> merge-recursive.c
> midx.c
> read-cache.c
> repo-settings.c
> repository.c
> repository.h
> sparse-index.c
> t/helper/test-read-cache.c
> t/helper/test-read-graph.c
> unpack-trees.c
> 
> or are their calls to prepare_repo_settings() only done after gitdir
> setup?  If the latter, perhaps the commit-graph function calls could
> be moved after gitdir setup too to avoid the need to do extra checks
> in it?
> 

>> Signed-off-by: Lessley Dennington <lessleydennington@gmail.com>
>> ---
>>   builtin/checkout.c     | 6 ++++--
>>   builtin/pack-objects.c | 9 ++++++---
>>   commit-graph.c         | 5 ++++-
>>   repo-settings.c        | 3 +++
>>   4 files changed, 17 insertions(+), 6 deletions(-)
>>
>> diff --git a/builtin/checkout.c b/builtin/checkout.c
>> index 8c69dcdf72a..31632b07888 100644
>> --- a/builtin/checkout.c
>> +++ b/builtin/checkout.c
>> @@ -1588,8 +1588,10 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
>>
>>          git_config(git_checkout_config, opts);
>>
>> -       prepare_repo_settings(the_repository);
>> -       the_repository->settings.command_requires_full_index = 0;
>> +       if (startup_info->have_repository) {
>> +               prepare_repo_settings(the_repository);
>> +               the_repository->settings.command_requires_full_index = 0;
>> +       }
>>
>>          opts->track = BRANCH_TRACK_UNSPECIFIED;
>>
>> diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
>> index 1a3dd445f83..45dc2258dc7 100644
>> --- a/builtin/pack-objects.c
>> +++ b/builtin/pack-objects.c
>> @@ -3976,9 +3976,12 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
>>          read_replace_refs = 0;
>>
>>          sparse = git_env_bool("GIT_TEST_PACK_SPARSE", -1);
>> -       prepare_repo_settings(the_repository);
>> -       if (sparse < 0)
>> -               sparse = the_repository->settings.pack_use_sparse;
>> +
>> +       if (startup_info->have_repository) {
>> +               prepare_repo_settings(the_repository);
>> +               if (sparse < 0)
>> +                       sparse = the_repository->settings.pack_use_sparse;
>> +       }
>>
>>          reset_pack_idx_option(&pack_idx_opts);
>>          git_config(git_pack_config, NULL);
>> diff --git a/commit-graph.c b/commit-graph.c
>> index 2706683acfe..265c010122e 100644
>> --- a/commit-graph.c
>> +++ b/commit-graph.c
>> @@ -632,10 +632,13 @@ static int prepare_commit_graph(struct repository *r)
>>          struct object_directory *odb;
>>
>>          /*
>> +        * Early return if there is no git dir or if the commit graph is
>> +        * disabled.
>> +        *
>>           * This must come before the "already attempted?" check below, because
>>           * we want to disable even an already-loaded graph file.
>>           */
>> -       if (r->commit_graph_disabled)
>> +       if (!r->gitdir || r->commit_graph_disabled)
>>                  return 0;
>>
>>          if (r->objects->commit_graph_attempted)
>> diff --git a/repo-settings.c b/repo-settings.c
>> index b93e91a212e..00ca5571a1a 100644
>> --- a/repo-settings.c
>> +++ b/repo-settings.c
>> @@ -17,6 +17,9 @@ void prepare_repo_settings(struct repository *r)
>>          char *strval;
>>          int manyfiles;
>>
>> +       if (!r->gitdir)
>> +               BUG("Cannot add settings for uninitialized repository");
>> +
>>          if (r->settings.initialized++)
>>                  return;
> 
> I'm not what the BUG() is trying to help us catch, but I'm worried
> that there are many additional places that now need workarounds to
> avoid triggering bugs.
>