Optimize performance for scanning trees in partial clones #5699
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In two of our test repositories in this file, we never commit the `.gitattributes` file and instead rely on the fact that `git lfs clone` sometimes processes all files in the working tree to determine which are pointer files. This is inefficient and we don't want to rely on this behaviour, especially since it differs from that of `git clone`, so fix our tests so that we explicitly commit the `.gitattributes` file.
Right now, if the user is using partial clone, our call to `git ls-tree` against HEAD is expensive because `git ls-tree` needs to download each blob, which it does incrementally instead of all at once. If we're scanning the tree from HEAD, then we can avoid the expense of doing this by running `git ls-files` with a pattern that matches only LFS files, which makes the operation much cheaper, since we avoid needing to download blobs for many of those objects. We can format the data such that it matches the pattern we expect for `git ls-tree` so that we can avoid modifying most of the calls and continue to let things function in the same way. Do so, but limit our changes to Git 2.42.0 and newer, since the `objecttype` argument is new in that version.
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chrisd8088
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Apr 17, 2024
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Right now, if the user is using partial clone, our call to
git ls-treeagainst HEAD is expensive becausegit ls-treeneeds to download each blob, which it does incrementally instead of all at once.If we're scanning the tree from HEAD, then we can avoid the expense of doing this by running
git ls-fileswith a pattern that matches only LFS files, which makes the operation much cheaper, since we avoid needing to download blobs for many of those objects. We can format the data such that it matches the pattern we expect forgit ls-treeso that we can avoid modifying most of the calls and continue to let things function in the same way. Do so, but limit our changes to Git 2.42.0 and newer, since theobjecttypeargument is new in that version.In addition, let's fix some tests which rely on an invalid assumption about how we discover and process LFS files.