Documentation/scalar.adoc

scalar(1)
=========

NAME
----
scalar - A tool for managing large Git repositories

SYNOPSIS
--------
[verse]
scalar clone [--single-branch] [--branch <main-branch>] [--full-clone]
	[--[no-]src] [--[no-]tags] [--[no-]maintenance] <url> [<enlistment>]
scalar list
scalar register [--[no-]maintenance] [<enlistment>]
scalar unregister [<enlistment>]
scalar run ( all | config | commit-graph | fetch | loose-objects | pack-files ) [<enlistment>]
scalar reconfigure [--maintenance=(enable|disable|keep)] [ --all | <enlistment> ]
scalar diagnose [<enlistment>]
scalar delete <enlistment>

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

Scalar is a repository management tool that optimizes Git for use in large
repositories. Scalar improves performance by configuring advanced Git settings,
maintaining repositories in the background, and helping to reduce data sent
across the network.

An important Scalar concept is the enlistment: this is the top-level directory
of the project. It usually contains the subdirectory `src/` which is a Git
worktree. This encourages the separation between tracked files (inside `src/`)
and untracked files, such as build artifacts (outside `src/`). When registering
an existing Git worktree with Scalar whose name is not `src`, the enlistment
will be identical to the worktree.

The `scalar` command implements various subcommands, and different options
depending on the subcommand. With the exception of `clone`, `list` and
`reconfigure --all`, all subcommands expect to be run in an enlistment.

The following options can be specified _before_ the subcommand:

-C <directory>::
	Before running the subcommand, change the working directory. This
	option imitates the same option of linkgit:git[1].

-c <key>=<value>::
	For the duration of running the specified subcommand, configure this
	setting. This option imitates the same option of linkgit:git[1].

COMMANDS
--------

Clone
~~~~~

clone [<options>] <url> [<enlistment>]::
	Clones the specified repository, similar to linkgit:git-clone[1]. By
	default, only commit and tree objects are cloned. Once finished, the
	worktree is located at `<enlistment>/src`.
+
The sparse-checkout feature is enabled (except when run with `--full-clone`)
and the only files present are those in the top-level directory. Use
`git sparse-checkout set` to expand the set of directories you want to see,
or `git sparse-checkout disable` to expand to all files (see
linkgit:git-sparse-checkout[1] for more details). You can explore the
subdirectories outside your sparse-checkout by using `git ls-tree
HEAD[:<directory>]`.

-b <name>::
--branch <name>::
	Instead of checking out the branch pointed to by the cloned
	repository's HEAD, check out the `<name>` branch instead.

--single-branch::
--no-single-branch::
	Clone only the history leading to the tip of a single branch, either
	specified by the `--branch` option or the primary branch remote's
	`HEAD` points at.
+
Further fetches into the resulting repository will only update the
remote-tracking branch for the branch this option was used for the initial
cloning. If the HEAD at the remote did not point at any branch when
`--single-branch` clone was made, no remote-tracking branch is created.

--src::
--no-src::
	By default, `scalar clone` places the cloned repository within a
	`<entlistment>/src` directory. Use `--no-src` to place the cloned
	repository directly in the `<enlistment>` directory.

--tags::
--no-tags::
	By default, `scalar clone` will fetch the tag objects advertised by
	the remote and future `git fetch` commands will do the same. Use
	`--no-tags` to avoid fetching tags in `scalar clone` and to configure
	the repository to avoid fetching tags in the future. To fetch tags after
	cloning with `--no-tags`, run `git fetch --tags`.

--full-clone::
--no-full-clone::
	A sparse-checkout is initialized by default. This behavior can be
	turned off via `--full-clone`.

--maintenance::
--no-maintenance::
	By default, `scalar clone` configures the enlistment to use Git's
	background maintenance feature. Use the `--no-maintenance` to skip
	this configuration.

List
~~~~

list::
	List enlistments that are currently registered by Scalar. This
	subcommand does not need to be run inside an enlistment.

Register
~~~~~~~~

register [<enlistment>]::
	Adds the enlistment's repository to the list of registered repositories
	and starts background maintenance. If `<enlistment>` is not provided,
	then the enlistment associated with the current working directory is
	registered.
+
Note: when this subcommand is called in a worktree that is called `src/`, its
parent directory is considered to be the Scalar enlistment. If the worktree is
_not_ called `src/`, it itself will be considered to be the Scalar enlistment.

--maintenance::
--no-maintenance::
	By default, `scalar register` configures the enlistment to use Git's
	background maintenance feature. Use the `--no-maintenance` to skip
	this configuration. This does not disable any maintenance that may
	already be enabled in other ways.

Unregister
~~~~~~~~~~

unregister [<enlistment>]::
	Remove the specified repository from the list of repositories
	registered with Scalar and stop the scheduled background maintenance.

Run
~~~

scalar run ( all | config | commit-graph | fetch | loose-objects | pack-files ) [<enlistment>]::
	Run the given maintenance task (or all tasks, if `all` was specified).
	Except for `all` and `config`, this subcommand simply hands off to
	linkgit:git-maintenance[1] (mapping `fetch` to `prefetch` and
	`pack-files` to `incremental-repack`).
+
These tasks are run automatically as part of the scheduled maintenance,
as soon as the repository is registered with Scalar. It should therefore
not be necessary to run this subcommand manually.
+
The `config` task is specific to Scalar and configures all those
opinionated default settings that make Git work more efficiently with
large repositories. As this task is run as part of `scalar clone`
automatically, explicit invocations of this task are rarely needed.

Reconfigure
~~~~~~~~~~~

After a Scalar upgrade, or when the configuration of a Scalar enlistment
was somehow corrupted or changed by mistake, this subcommand allows to
reconfigure the enlistment.

--all::
	When `--all` is specified, reconfigure all enlistments currently
	registered with Scalar by the `scalar.repo` config key. Use this
	option after each upgrade to get the latest features.

--maintenance=(enable|disable|keep)::
	By default, Scalar configures the enlistment to use Git's
	background maintenance feature; this is the same as using the
	`enable` value for this option. Use the	`disable` value to
	remove each considered enlistment from background maintenance.
	Use `keep' to leave the background maintenance configuration
	untouched for these repositories.

Diagnose
~~~~~~~~

diagnose [<enlistment>]::
    When reporting issues with Scalar, it is often helpful to provide the
    information gathered by this command, including logs and certain
    statistics describing the data shape of the current enlistment.
+
The output of this command is a `.zip` file that is written into
a directory adjacent to the worktree in the `src` directory.

Delete
~~~~~~

delete <enlistment>::
	This subcommand lets you delete an existing Scalar enlistment from your
	local file system, unregistering the repository.

RECOMMENDED CONFIG VALUES
-------------------------

As part of both `scalar clone` and `scalar register`, certain Git config
values are set to optimize for large repositories or cross-platform support.
These options are updated in new Git versions according to the best known
advice for large repositories, and users can get the latest recommendations
by running `scalar reconfigure [--all]`.

This section lists justifications for the config values that are set in the
latest version.

am.keepCR=true::
	This setting is important for cross-platform development across Windows
	and non-Windows platforms and keeping carriage return (`\r`) characters
	in certain workflows.

commitGraph.changedPaths=true::
	This setting helps the background maintenance steps that compute the
	serialized commit-graph to also store changed-path Bloom filters. This
	accelerates file history commands and allows users to automatically
	benefit without running a foreground command.

commitGraph.generationVersion=1::
	While the preferred version is 2 for performance reasons, existing users
	that had version 1 by default will need special care in upgrading to
	version 2. This is likely to change in the future as the upgrade story
	solidifies.

core.autoCRLF=false::
	This removes the transformation of worktree files to add CRLF line
	endings when only LF line endings exist. This is removed for performance
	reasons. Repositories that use tools that care about CRLF line endings
	should commit the necessary files with those line endings instead.

core.logAllRefUpdates=true::
	This enables the reflog on all branches. While this is a performance
	cost for large repositories, it is frequently an important data source
	for users to get out of bad situations or to seek support from experts.

core.safeCRLF=false::
	Similar to `core.autoCRLF=false`, this disables checks around whether
	the CRLF conversion is reversible. This is a performance improvement,
	but can be dangerous if `core.autoCRLF` is reenabled by the user.

credential.https://dev.azure.com.useHttpPath=true::
	This setting enables the `credential.useHttpPath` feature only for web
	URLs for Azure DevOps. This is important for users interacting with that
	service using multiple organizations and thus multiple credential
	tokens.

feature.experimental=false::
	This disables the "experimental" optimizations grouped under this
	feature config. The expectation is that all valuable optimizations are
	also set explicitly by Scalar config, and any differences are
	intentional. Notable differences include several bitmap-related config
	options which are disabled for client-focused Scalar repos.

feature.manyFiles=false::
	This disables the "many files" optimizations grouped under this feature
	config. The expectation is that all valuable optimizations are also set
	explicitly by Scalar config, and any differences are intentional.

fetch.showForcedUpdates=false::
	This disables the check at the end of `git fetch` that notifies the user
	if the ref update was a forced update (one where the previous position
	is not reachable from the latest position). This check can be very
	expensive in large repositories, so is disabled and replaced with an
	advice message. Set `advice.fetchShowForcedUpdates=false` to disable
	this advice message.

fetch.unpackLimit=1::
	This setting prevents Git from unpacking packfiles into loose objects
	as they are downloaded from the server. The default limit of 100 was
	intended as a way to prevent performance issues from too many packfiles,
	but Scalar uses background maintenance to group packfiles and cover them
	with a multi-pack-index, removing this issue.

fetch.writeCommitGraph=false::
	This config setting was created to help users automatically update their
	commit-graph files as they perform fetches. However, this takes time
	from foreground fetches and pulls and Scalar uses background maintenance
	for this function instead.

gc.auto=0::
	This disables automatic garbage collection, since Scalar uses background
	maintenance to keep the repository data in good shape.

gui.GCWarning=false::
	Since Scalar disables garbage collection by setting `gc.auto=0`, the
	`git-gui` tool may start to warn about this setting. Disable this
	warning as Scalar's background maintenance configuration makes the
	warning irrelevant.

index.skipHash=true::
	Disable computing the hash of the index contents as it is being written.
	This assists with performance, especially for large index files.

index.threads=true::
	This tells Git to automatically detect how many threads it should use
	when reading the index due to the default value of `core.preloadIndex`,
	which enables parallel index reads. This explicit setting also enables
	`index.recordOffsetTable=true` to speed up parallel index reads.

index.version=4::
	This index version adds compression to the path names, reducing the size
	of the index in a significant way for large repos. This is an important
	performance boost.

log.excludeDecoration=refs/prefetch/*::
	Since Scalar enables background maintenance with the `incremental`
	strategy, this setting avoids polluting `git log` output with refs
	stored by the background prefetch operations.

merge.renames=true::
	When computing merges in large repos, it is particularly important to
	detect renames to maximize the potential for a result that will validate
	correctly. Users performing merges locally are more likely to be doing
	so because a server-side merge (via pull request or similar) resulted in
	conflicts. While this is the default setting, it is set specifically to
	override a potential change to `diff.renames` which a user may set for
	performance reasons.

merge.stat=false::
	This disables a diff output after computing a merge. This improves
	performance of `git merge` for large repos while reducing noisy output.

pack.useBitmaps=false::
	This disables the use of `.bitmap` files attached to packfiles. Bitmap
	files are optimized for server-side use, not client-side use. Scalar
	disables this to avoid some performance issues that can occur if a user
	accidentally creates `.bitmap` files.

pack.usePathWalk=true::
	This enables the `--path-walk` option to `git pack-objects` by default.
	This can accelerate the computation and compression of packfiles created
	by `git push` and other repack operations.

receive.autoGC=false::
	Similar to `gc.auto`, this setting is disabled in preference of
	background maintenance.

status.aheadBehind=false::
	This disables the ahead/behind calculation that would normally happen
	during a `git status` command. This information is frequently ignored by
	users but can be expensive to calculate in large repos that receive
	thousands of commits per day. The calculation is replaced with an advice
	message that can be disabled by disabling the `advice.statusAheadBehind`
	config.

The following settings are different based on which platform is in use:

core.untrackedCache=(true|false)::
	The untracked cache feature is important for performance benefits on
	large repositories, but has demonstrated some bugs on Windows
	filesystems. Thus, this is set for other platforms but disabled on
	Windows.

http.sslBackend=schannel::
	On Windows, the `openssl` backend has some issues with certain types of
	remote providers and certificate types. Override the default setting to
	avoid these common problems.


SEE ALSO
--------
linkgit:git-clone[1], linkgit:git-maintenance[1].

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