git/Documentation/config/extensions.txt

extensions.objectFormat::
	Specify the hash algorithm to use.  The acceptable values are `sha1` and
	`sha256`.  If not specified, `sha1` is assumed.  It is an error to specify
	this key unless `core.repositoryFormatVersion` is 1.
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Note that this setting should only be set by linkgit:git-init[1] or
linkgit:git-clone[1].  Trying to change it after initialization will not
work and will produce hard-to-diagnose issues.

extensions.compatObjectFormat::

	Specify a compatitbility hash algorithm to use.  The acceptable values
	are `sha1` and `sha256`.  The value specified must be different from the
	value of extensions.objectFormat.  This allows client level
	interoperability between git repositories whose objectFormat matches
	this compatObjectFormat.  In particular when fully implemented the
	pushes and pulls from a repository in whose objectFormat matches
	compatObjectFormat.  As well as being able to use oids encoded in
	compatObjectFormat in addition to oids encoded with objectFormat to
	locally specify objects.

extensions.refStorage::
	Specify the ref storage format to use. The acceptable values are:
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include::../ref-storage-format.txt[]
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It is an error to specify this key unless `core.repositoryFormatVersion` is 1.
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Note that this setting should only be set by linkgit:git-init[1] or
linkgit:git-clone[1]. Trying to change it after initialization will not
work and will produce hard-to-diagnose issues.

extensions.worktreeConfig::
	If enabled, then worktrees will load config settings from the
	`$GIT_DIR/config.worktree` file in addition to the
	`$GIT_COMMON_DIR/config` file. Note that `$GIT_COMMON_DIR` and
	`$GIT_DIR` are the same for the main working tree, while other
	working trees have `$GIT_DIR` equal to
	`$GIT_COMMON_DIR/worktrees/<id>/`. The settings in the
	`config.worktree` file will override settings from any other
	config files.
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When enabling `extensions.worktreeConfig`, you must be careful to move
certain values from the common config file to the main working tree's
`config.worktree` file, if present:
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* `core.worktree` must be moved from `$GIT_COMMON_DIR/config` to
  `$GIT_COMMON_DIR/config.worktree`.
* If `core.bare` is true, then it must be moved from `$GIT_COMMON_DIR/config`
  to `$GIT_COMMON_DIR/config.worktree`.
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It may also be beneficial to adjust the locations of `core.sparseCheckout`
and `core.sparseCheckoutCone` depending on your desire for customizable
sparse-checkout settings for each worktree. By default, the `git
sparse-checkout` builtin enables `extensions.worktreeConfig`, assigns
these config values on a per-worktree basis, and uses the
`$GIT_DIR/info/sparse-checkout` file to specify the sparsity for each
worktree independently. See linkgit:git-sparse-checkout[1] for more
details.
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For historical reasons, `extensions.worktreeConfig` is respected
regardless of the `core.repositoryFormatVersion` setting.