submodule--helper: fix initialization of warn_if_uninitialized

[git.git] / Documentation / git-sparse-checkout.txt

git-sparse-checkout(1)
======================

NAME
----
git-sparse-checkout - Reduce your working tree to a subset of tracked files


SYNOPSIS
--------
[verse]
'git sparse-checkout <subcommand> [<options>]'


DESCRIPTION
-----------

This command is used to create sparse checkouts, which means that it
changes the working tree from having all tracked files present, to only
have a subset of them.  It can also switch which subset of files are
present, or undo and go back to having all tracked files present in the
working copy.

The subset of files is chosen by providing a list of directories in
cone mode (which is recommended), or by providing a list of patterns
in non-cone mode.

When in a sparse-checkout, other Git commands behave a bit differently.
For example, switching branches will not update paths outside the
sparse-checkout directories/patterns, and `git commit -a` will not record
paths outside the sparse-checkout directories/patterns as deleted.

THIS COMMAND IS EXPERIMENTAL. ITS BEHAVIOR, AND THE BEHAVIOR OF OTHER
COMMANDS IN THE PRESENCE OF SPARSE-CHECKOUTS, WILL LIKELY CHANGE IN
THE FUTURE.


COMMANDS
--------
'list'::
        Describe the directories or patterns in the sparse-checkout file.

'set'::
        Enable the necessary sparse-checkout config settings
        (`core.sparseCheckout`, `core.sparseCheckoutCone`, and
        `index.sparse`) if they are not already set to the desired values,
        and write a set of patterns to the sparse-checkout file from the
        list of arguments following the 'set' subcommand. Update the
        working directory to match the new patterns.
+
To ensure that adjusting the sparse-checkout settings within a worktree
does not alter the sparse-checkout settings in other worktrees, the 'set'
subcommand will upgrade your repository config to use worktree-specific
config if not already present. The sparsity defined by the arguments to
the 'set' subcommand are stored in the worktree-specific sparse-checkout
file. See linkgit:git-worktree[1] and the documentation of
`extensions.worktreeConfig` in linkgit:git-config[1] for more details.
+
When the `--stdin` option is provided, the directories or patterns are
read from standard in as a newline-delimited list instead of from the
arguments.
+
When `--cone` is passed or `core.sparseCheckoutCone` is enabled, the
input list is considered a list of directories.  This allows for
better performance with a limited set of patterns (see 'CONE PATTERN
SET' below).  The input format matches the output of `git ls-tree
--name-only`.  This includes interpreting pathnames that begin with a
double quote (") as C-style quoted strings.  Note that the set command
will write patterns to the sparse-checkout file to include all files
contained in those directories (recursively) as well as files that are
siblings of ancestor directories. This may become the default in the
future; --no-cone can be passed to request non-cone mode.
+
When `--no-cone` is passed or `core.sparseCheckoutCone` is not enabled,
the input list is considered a list of patterns.  This mode is harder
to use and less performant, and is thus not recommended.  See the
"Sparse Checkout" section of linkgit:git-read-tree[1] and the "Pattern
Set" sections below for more details.
+
Use the `--[no-]sparse-index` option to use a sparse index (the
default is to not use it).  A sparse index reduces the size of the
index to be more closely aligned with your sparse-checkout
definition. This can have significant performance advantages for
commands such as `git status` or `git add`.  This feature is still
experimental. Some commands might be slower with a sparse index until
they are properly integrated with the feature.
+
**WARNING:** Using a sparse index requires modifying the index in a way
that is not completely understood by external tools. If you have trouble
with this compatibility, then run `git sparse-checkout init --no-sparse-index`
to rewrite your index to not be sparse. Older versions of Git will not
understand the sparse directory entries index extension and may fail to
interact with your repository until it is disabled.

'add'::
        Update the sparse-checkout file to include additional directories
        (in cone mode) or patterns (in non-cone mode).  By default, these
        directories or patterns are read from the command-line arguments,
        but they can be read from stdin using the `--stdin` option.

'reapply'::
        Reapply the sparsity pattern rules to paths in the working tree.
        Commands like merge or rebase can materialize paths to do their
        work (e.g. in order to show you a conflict), and other
        sparse-checkout commands might fail to sparsify an individual file
        (e.g. because it has unstaged changes or conflicts).  In such
        cases, it can make sense to run `git sparse-checkout reapply` later
        after cleaning up affected paths (e.g. resolving conflicts, undoing
        or committing changes, etc.).
+
The `reapply` command can also take `--[no-]cone` and `--[no-]sparse-index`
flags, with the same meaning as the flags from the `set` command, in order
to change which sparsity mode you are using without needing to also respecify
all sparsity paths.

'disable'::
        Disable the `core.sparseCheckout` config setting, and restore the
        working directory to include all files.

'init'::
        Deprecated command that behaves like `set` with no specified paths.
        May be removed in the future.
+
Historically, `set` did not handle all the necessary config settings,
which meant that both `init` and `set` had to be called.  Invoking
both meant the `init` step would first remove nearly all tracked files
(and in cone mode, ignored files too), then the `set` step would add
many of the tracked files (but not ignored files) back.  In addition
to the lost files, the performance and UI of this combination was
poor.
+
Also, historically, `init` would not actually initialize the
sparse-checkout file if it already existed.  This meant it was
possible to return to a sparse-checkout without remembering which
paths to pass to a subsequent 'set' or 'add' command.  However,
`--cone` and `--sparse-index` options would not be remembered across
the disable command, so the easy restore of calling a plain `init`
decreased in utility.

SPARSE CHECKOUT
---------------

"Sparse checkout" allows populating the working directory sparsely.  It
uses the skip-worktree bit (see linkgit:git-update-index[1]) to tell Git
whether a file in the working directory is worth looking at. If the
skip-worktree bit is set, and the file is not present in the working tree,
then its absence is ignored. Git will avoid populating the contents of
those files, which makes a sparse checkout helpful when working in a
repository with many files, but only a few are important to the current
user.

The `$GIT_DIR/info/sparse-checkout` file is used to define the
skip-worktree reference bitmap. When Git updates the working
directory, it updates the skip-worktree bits in the index based
on this file. The files matching the patterns in the file will
appear in the working directory, and the rest will not.

To enable the sparse-checkout feature, run `git sparse-checkout set` to
set the patterns you want to use.

To repopulate the working directory with all files, use the
`git sparse-checkout disable` command.


FULL PATTERN SET
----------------

By default, the sparse-checkout file uses the same syntax as `.gitignore`
files.

While `$GIT_DIR/info/sparse-checkout` is usually used to specify what
files are included, you can also specify what files are _not_ included,
using negative patterns. For example, to remove the file `unwanted`:

----------------
/*
!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.sparseCheckoutCone` 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."

When in cone mode, the `git sparse-checkout set` subcommand takes a list of
directories instead of a list of sparse-checkout patterns. In this mode,
the command `git sparse-checkout set A/B/C` sets the directory `A/B/C` as
a recursive pattern, the directories `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.

In the cone mode case, the `git sparse-checkout list` subcommand will list the
directories that define the recursive patterns. For the example sparse-checkout
file above, the output is as follows:

--------------------------
$ git sparse-checkout list
A/B/C
--------------------------

If `core.ignoreCase=true`, then the pattern-matching algorithm will use a
case-insensitive check. This corrects for case mismatched filenames in the
'git sparse-checkout set' command to reflect the expected cone in the working
directory.

When changing the sparse-checkout patterns in cone mode, Git will inspect each
tracked directory that is not within the sparse-checkout cone to see if it
contains any untracked files. If all of those files are ignored due to the
`.gitignore` patterns, then the directory will be deleted. If any of the
untracked files within that directory is not ignored, then no deletions will
occur within that directory and a warning message will appear. If these files
are important, then reset your sparse-checkout definition so they are included,
use `git add` and `git commit` to store them, then remove any remaining files
manually to ensure Git can behave optimally.


SUBMODULES
----------

If your repository contains one or more submodules, then submodules
are populated based on interactions with the `git submodule` command.
Specifically, `git submodule init -- <path>` will ensure the submodule
at `<path>` is present, while `git submodule deinit [-f] -- <path>`
will remove the files for the submodule at `<path>` (including any
untracked files, uncommitted changes, and unpushed history).  Similar
to how sparse-checkout removes files from the working tree but still
leaves entries in the index, deinitialized submodules are removed from
the working directory but still have an entry in the index.

Since submodules may have unpushed changes or untracked files,
removing them could result in data loss.  Thus, changing sparse
inclusion/exclusion rules will not cause an already checked out
submodule to be removed from the working copy.  Said another way, just
as `checkout` will not cause submodules to be automatically removed or
initialized even when switching between branches that remove or add
submodules, using `sparse-checkout` to reduce or expand the scope of
"interesting" files will not cause submodules to be automatically
deinitialized or initialized either.

Further, the above facts mean that there are multiple reasons that
"tracked" files might not be present in the working copy: sparsity
pattern application from sparse-checkout, and submodule initialization
state.  Thus, commands like `git grep` that work on tracked files in
the working copy may return results that are limited by either or both
of these restrictions.


SEE ALSO
--------

linkgit:git-read-tree[1]
linkgit:gitignore[5]

GIT
---
Part of the linkgit:git[1] suite