git/Documentation/config/sparse.txt

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repo_read_index: add config to expect files outside sparse patterns Typically with sparse checkouts, we expect files outside the sparsity patterns to be marked as SKIP_WORKTREE and be missing from the working tree. Sometimes this expectation would be violated however; including in cases such as: * users grabbing files from elsewhere and writing them to the worktree (perhaps by editing a cached copy in an editor, copying/renaming, or even untarring) * various git commands having incomplete or no support for the SKIP_WORKTREE bit[1,2] * users attempting to "abort" a sparse-checkout operation with a not-so-early Ctrl+C (updating $GIT_DIR/info/sparse-checkout and the working tree is not atomic)[3]. When the SKIP_WORKTREE bit in the index did not reflect the presence of the file in the working tree, it traditionally caused confusion and was difficult to detect and recover from. So, in a sparse checkout, since af6a51875a (repo_read_index: clear SKIP_WORKTREE bit from files present in worktree, 2022-01-14), Git automatically clears the SKIP_WORKTREE bit at index read time for entries corresponding to files that are present in the working tree. There is another workflow, however, where it is expected that paths outside the sparsity patterns appear to exist in the working tree and that they do not lose the SKIP_WORKTREE bit, at least until they get modified. A Git-aware virtual file system[4] takes advantage of its position as a file system driver to expose all files in the working tree, fetch them on demand using partial clone on access, and tell Git to pay attention to them on demand by updating the sparse checkout pattern on writes. This means that commands like "git status" only have to examine files that have potentially been modified, whereas commands like "ls" are able to show the entire codebase without requiring manual updates to the sparse checkout pattern. Thus since af6a51875a, Git with such Git-aware virtual file systems unsets the SKIP_WORKTREE bit for all files and commands like "git status" have to fetch and examine them all. Introduce a configuration setting sparse.expectFilesOutsideOfPatterns to allow limiting the tracked set of files to a small set once again. A Git-aware virtual file system or other application that wants to maintain files outside of the sparse checkout can set this in a repository to instruct Git not to check for the presence of SKIP_WORKTREE files. The setting defaults to false, so most users of sparse checkout will still get the benefit of an automatically updating index to recover from the variety of difficult issues detailed in af6a51875a for paths with SKIP_WORKTREE set despite the path being present. [1] https://lore.kernel.org/git/xmqqbmb1a7ga.fsf@gitster-ct.c.googlers.com/ [2] The three long paragraphs in the middle of https://lore.kernel.org/git/CABPp-BH9tju7WVm=QZDOvaMDdZbpNXrVWQdN-jmfN8wC6YVhmw@mail.gmail.com/ [3] https://lore.kernel.org/git/CABPp-BFnFpzwGC11TLoLs8YK5yiisA5D5-fFjXnJsbESVDwZsA@mail.gmail.com/ [4] such as the vfsd described in https://lore.kernel.org/git/20220207190320.2960362-1-jonathantanmy@google.com/ Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Elijah Newren <newren@gmail.com> Reviewed-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-02-26 14:12:22 +08:00
sparse.expectFilesOutsideOfPatterns::
Typically with sparse checkouts, files not matching any
sparsity patterns are marked with a SKIP_WORKTREE bit in the
index and are missing from the working tree. Accordingly, Git
will ordinarily check whether files with the SKIP_WORKTREE bit
are in fact present in the working tree contrary to
expectations. If Git finds any, it marks those paths as
present by clearing the relevant SKIP_WORKTREE bits. This
option can be used to tell Git that such
present-despite-skipped files are expected and to stop
checking for them.
+
The default is `false`, which allows Git to automatically recover
from the list of files in the index and working tree falling out of
sync.
+
Set this to `true` if you are in a setup where some external factor
relieves Git of the responsibility for maintaining the consistency
between the presence of working tree files and sparsity patterns. For
example, if you have a Git-aware virtual file system that has a robust
mechanism for keeping the working tree and the sparsity patterns up to
date based on access patterns.
+
Regardless of this setting, Git does not check for
present-despite-skipped files unless sparse checkout is enabled, so
this config option has no effect unless `core.sparseCheckout` is
`true`.