On 10/6/2019 12:22 AM, Elijah Newren wrote:
> On Thu, Sep 19, 2019 at 1:45 PM Derrick Stolee via GitGitGadget
> <gitgitgad...@gmail.com> wrote:
>>
>> From: Derrick Stolee <dsto...@microsoft.com>
>>
>> The sparse-checkout feature can have quadratic performance as
>> the number of patterns and number of entries in the index grow.
>> If there are 1,000 patterns and 1,000,000 entries, this time can
>> be very significant.
>>
>> Create a new Boolean config option, core.sparseCheckoutCone, to
>> indicate that we expect the sparse-checkout file to contain a
>> more limited set of patterns. This is a separate config setting
>> from core.sparseCheckout to avoid breaking older clients by
>> introcuding a tri-state option.
>
> s/introcuding/introducing/
>
>> The config option does nothing right now, but will be expanded
>> upon in a later commit.
>>
>> Signed-off-by: Derrick Stolee <dsto...@microsoft.com>
>> ---
>> Documentation/config/core.txt | 7 ++--
>> Documentation/git-sparse-checkout.txt | 50 +++++++++++++++++++++++++++
>> cache.h | 4 ++-
>> config.c | 5 +++
>> environment.c | 1 +
>> t/t1091-sparse-checkout-builtin.sh | 14 ++++++++
>> 6 files changed, 78 insertions(+), 3 deletions(-)
>>
>> diff --git a/Documentation/config/core.txt b/Documentation/config/core.txt
>> index 75538d27e7..9b8ab2a6d4 100644
>> --- a/Documentation/config/core.txt
>> +++ b/Documentation/config/core.txt
>> @@ -591,8 +591,11 @@ core.multiPackIndex::
>> multi-pack-index design document].
>>
>> core.sparseCheckout::
>> - Enable "sparse checkout" feature. See section "Sparse checkout" in
>> - linkgit:git-read-tree[1] for more information.
>> + Enable "sparse checkout" feature. If "false", then sparse-checkout
>> + is disabled. If "true", then sparse-checkout is enabled with the full
>> + .gitignore pattern set. If "cone", then sparse-checkout is enabled
>> with
>> + a restricted pattern set. See linkgit:git-sparse-checkout[1] for more
>> + information.
>
> This isn't consistent with the commit message that suggests it's a new
> option rather than a new possible value for an old option.
Thanks for the catch. I forgot to update the docs. Fixed for v3.
>> core.abbrev::
>> Set the length object names are abbreviated to. If
>> diff --git a/Documentation/git-sparse-checkout.txt
>> b/Documentation/git-sparse-checkout.txt
>> index da95b28b1c..757326618d 100644
>> --- a/Documentation/git-sparse-checkout.txt
>> +++ b/Documentation/git-sparse-checkout.txt
>> @@ -87,6 +87,56 @@ using negative patterns. For example, to remove the file
>> `unwanted`:
>> ----------------
>>
>>
>> +## CONE PATTERN SET
>> +
>> +The full pattern set allows for arbitrary pattern matches and complicated
>> +inclusion/exclusion rules. These can result in O(N*M) pattern matches when
>> +updating the index, where N is the number of patterns and M is the number
>> +of paths in the index. To combat this performance issue, a more restricted
>> +pattern set is allowed when `core.spareCheckoutCone` is enabled.
>> +
>> +The accepted patterns in the cone pattern set are:
>> +
>> +1. *Recursive:* All paths inside a directory are included.
>> +
>> +2. *Parent:* All files immediately inside a directory are included.
>> +
>> +In addition to the above two patterns, we also expect that all files in the
>> +root directory are included. If a recursive pattern is added, then all
>> +leading directories are added as parent patterns.
>> +
>> +By default, when running `git sparse-checkout init`, the root directory is
>> +added as a parent pattern. At this point, the sparse-checkout file contains
>> +the following patterns:
>> +
>> +```
>> +/*
>> +!/*/
>> +```
>> +
>> +This says "include everything in root, but nothing two levels below root."
>> +If we then add the folder `A/B/C` as a recursive pattern, the folders `A`
>> and
>> +`A/B` are added as parent patterns. The resulting sparse-checkout file is
>> +now
>> +
>> +```
>> +/*
>> +!/*/
>> +/A/
>> +!/A/*/
>> +/A/B/
>> +!/A/B/*/
>> +/A/B/C/
>> +```
>> +
>> +Here, order matters, so the negative patterns are overridden by the positive
>> +patterns that appear lower in the file.
>> +
>> +If `core.sparseCheckoutCone=true`, then Git will parse the sparse-checkout
>> file
>> +expecting patterns of these types. Git will warn if the patterns do not
>> match.
>> +If the patterns do match the expected format, then Git will use faster hash-
>> +based algorithms to compute inclusion in the sparse-checkout.
>> +
>> SEE ALSO
>> --------
>>
>> diff --git a/cache.h b/cache.h
>> index cf5d70c196..8e8ea67efa 100644
>> --- a/cache.h
>> +++ b/cache.h
>> @@ -911,12 +911,14 @@ extern char *git_replace_ref_base;
>>
>> extern int fsync_object_files;
>> extern int core_preload_index;
>> -extern int core_apply_sparse_checkout;
>> extern int precomposed_unicode;
>> extern int protect_hfs;
>> extern int protect_ntfs;
>> extern const char *core_fsmonitor;
>>
>> +int core_apply_sparse_checkout;
>> +int core_sparse_checkout_cone;
>> +
>> /*
>> * Include broken refs in all ref iterations, which will
>> * generally choke dangerous operations rather than letting
>> diff --git a/config.c b/config.c
>> index 296a6d9cc4..f65c74f5b7 100644
>> --- a/config.c
>> +++ b/config.c
>> @@ -1329,6 +1329,11 @@ static int git_default_core_config(const char *var,
>> const char *value, void *cb)
>> return 0;
>> }
>>
>> + if (!strcmp(var, "core.sparsecheckoutcone")) {
>> + core_sparse_checkout_cone = git_config_bool(var, value);
>> + return 0;
>> + }
>> +
>> if (!strcmp(var, "core.precomposeunicode")) {
>> precomposed_unicode = git_config_bool(var, value);
>> return 0;
>> diff --git a/environment.c b/environment.c
>> index 89af47cb85..670d92bcc0 100644
>> --- a/environment.c
>> +++ b/environment.c
>> @@ -69,6 +69,7 @@ enum object_creation_mode object_creation_mode =
>> OBJECT_CREATION_MODE;
>> char *notes_ref_name;
>> int grafts_replace_parents = 1;
>> int core_apply_sparse_checkout;
>> +int core_sparse_checkout_cone;
>> int merge_log_config = -1;
>> int precomposed_unicode = -1; /* see probe_utf8_pathname_composition() */
>> unsigned long pack_size_limit_cfg;
>> diff --git a/t/t1091-sparse-checkout-builtin.sh
>> b/t/t1091-sparse-checkout-builtin.sh
>> index 22fa032d6d..9b089c98c4 100755
>> --- a/t/t1091-sparse-checkout-builtin.sh
>> +++ b/t/t1091-sparse-checkout-builtin.sh
>> @@ -140,6 +140,20 @@ test_expect_success 'set sparse-checkout using --stdin'
>> '
>> test_cmp expect dir
>> '
>>
>> +test_expect_success 'cone mode: match patterns' '
>> + git -C repo config --worktree core.sparseCheckoutCone true &&
>> + rm -rf repo/a repo/folder1 repo/folder2 &&
>> + git -C repo read-tree -mu HEAD &&
>> + git -C repo reset --hard &&
>> + ls repo >dir &&
>> + cat >expect <<-EOF &&
>> + a
>> + folder1
>> + folder2
>> + EOF
>> + test_cmp expect dir
>> +'
>> +
>> test_expect_success 'sparse-checkout disable' '
>> git -C repo sparse-checkout disable &&
>> test_path_is_missing repo/.git/info/sparse-checkout &&
>> --
>> gitgitgadget
>
> What if core.sparseCheckoutCone is true but core.sparseCheckout is
> false? Is that an error case we warn the user about, or do we make
> sense of it somehow?
`core.sparseCheckoutCone` means "when you are doing sparse-checkout things,
try to use the fast logic assuming you have the cone patterns." It does not
enable the sparse-checkout on its own. It only changes run-time performance.
This is important for compatibility with other clients that will only look
at `core.sparseCheckout`.
Thanks,
-Stolee
