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scalar: add docs from microsoft/scalar
These docs have been altered to fit the version implemented in C within microsoft/git. This means in particular that the advanced.md file no longer applied at all. Some other areas were removed or significantly edited. Signed-off-by: Derrick Stolee <[email protected]>
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‎contrib/scalar/docs/faq.md‎

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Frequently Asked Questions
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==========================
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Using Scalar
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------------
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### I don't want a sparse clone, I want every file after I clone!
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Run `scalar clone --full-clone <url>` to initialize your repo to include
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every file. You can switch to a sparse-checkout later by running
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`git sparse-checkout init --cone`.
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### I already cloned without `--full-clone`. How do I get everything?
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Run `git sparse-checkout disable`.
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Scalar Design Decisions
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-----------------------
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There may be many design decisions within Scalar that are confusing at first
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glance. Some of them may cause friction when you use Scalar with your existing
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repos and existing habits.
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> Scalar has the most benefit when users design repositories
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> with efficient patterns.
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For example: Scalar uses the sparse-checkout feature to limit the size of the
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working directory within a large monorepo. It is designed to work efficiently
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with monorepos that are highly componentized, allowing most developers to
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need many fewer files in their daily work.
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### Why does `scalar clone` create a `<repo>/src` folder?
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Scalar uses a file system watcher to keep track of changes under this `src` folder.
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Any activity in this folder is assumed to be important to Git operations. By
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creating the `src` folder, we are making it easy for your build system to
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create output folders outside the `src` directory. We commonly see systems
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create folders for build outputs and package downloads. Scalar itself creates
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these folders during its builds.
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Your build system may create build artifacts such as `.obj` or `.lib` files
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next to your source code. These are commonly "hidden" from Git using
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`.gitignore` files. Having such artifacts in your source tree creates
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additional work for Git because it needs to look at these files and match them
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against the `.gitignore` patterns.
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By following the `src` pattern Scalar tries to establish and placing your build
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intermediates and outputs parallel with the `src` folder and not inside it,
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you can help optimize Git command performance for developers in the repository
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by limiting the number of files Git needs to consider for many common
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operations.

‎contrib/scalar/docs/getting-started.md‎

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Getting Started
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===============
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Registering existing Git repos
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------------------------------
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To add a repository to the list of registered repos, run `scalar register [<path>]`.
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If `<path>` is not provided, then the "current repository" is discovered from
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the working directory by scanning the parent paths for a path containing a `.git`
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folder, possibly inside a `src` folder.
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To see which repositories are currently tracked by the service, run
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`scalar list`.
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Run `scalar unregister [<path>]` to remove the repo from this list.
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Creating a new Scalar clone
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---------------------------------------------------
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The `clone` verb creates a local enlistment of a remote repository using the
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partial clone feature available e.g. on GitHub.
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```
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scalar clone [options] <url> [<dir>]
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```
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Create a local copy of the repository at `<url>`. If specified, create the `<dir>`
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directory and place the repository there. Otherwise, the last section of the `<url>`
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will be used for `<dir>`.
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At the end, the repo is located at `<dir>/src`. By default, the sparse-checkout
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feature is enabled and the only files present are those in the root of your
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Git repository. Use `git sparse-checkout set` to expand the set of directories
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you want to see, or `git sparse-checkout disable` to expand to all files. You
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can explore the subdirectories outside your sparse-checkout specification using
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`git ls-tree HEAD`.
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### Sparse Repo Mode
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By default, Scalar reduces your working directory to only the files at the
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root of the repository. You need to add the folders you care about to build up
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to your working set.
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* `scalar clone <url>`
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* Please choose the **Clone with HTTPS** option in the `Clone Repository` dialog in Azure Repos, not **Clone with SSH**.
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* `cd <root>\src`
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* At this point, your `src` directory only contains files that appear in your root
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tree. No folders are populated.
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* Set the directory list for your sparse-checkout using:
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1. `git sparse-checkout set <dir1> <dir2> ...`
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2. `git sparse-checkout set --stdin < dir-list.txt`
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* Run git commands as you normally would.
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* To fully populate your working directory, run `git sparse-checkout disable`.
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If instead you want to start with all files on-disk, you can clone with the
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`--full-clone` option. To enable sparse-checkout after the fact, run
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`git sparse-checkout init --cone`. This will initialize your sparse-checkout
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patterns to only match the files at root.
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If you are unfamiliar with what directories are available in the repository,
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then you can run `git ls-tree -d --name-only HEAD` to discover the directories
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at root, or `git ls-tree -d --name-only HEAD <path>` to discover the directories
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in `<path>`.
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### Options
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These options allow a user to customize their initial enlistment.
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* `--full-clone`: If specified, do not initialize the sparse-checkout feature.
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All files will be present in your `src` directory. This uses a Git partial
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clone: blobs are downloaded on demand.
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* `--branch=<ref>`: Specify the branch to checkout after clone.
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### Advanced Options
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The options below are not intended for use by a typical user. These are
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usually used by build machines to create a temporary enlistment that
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operates on a single commit.
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* `--single-branch`: Use this option to only download metadata for the branch
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that will be checked out. This is helpful for build machines that target
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a remote with many branches. Any `git fetch` commands after the clone will
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still ask for all branches.
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Removing a Scalar Clone
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-----------------------
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Since the `scalar clone` command sets up a file-system watcher (when available),
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that watcher could prevent deleting the enlistment. Run `scalar delete <path>`
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from outside of your enlistment to unregister the enlistment from the filesystem
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watcher and delete the enlistment at `<path>`.

‎contrib/scalar/docs/index.md‎

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Scalar: Enabling Git at Scale
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=============================
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Scalar is a tool that helps Git scale to some of the largest Git repositories.
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It achieves this by enabling some advanced Git features, such as:
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* *Partial clone:* reduces time to get a working repository by not
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downloading all Git objects right away.
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* *Background prefetch:* downloads Git object data from all remotes every
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hour, reducing the amount of time for foreground `git fetch` calls.
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* *Sparse-checkout:* limits the size of your working directory.
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* *File system monitor:* tracks the recently modified files and eliminates
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the need for Git to scan the entire worktree.
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* *Commit-graph:* accelerates commit walks and reachability calculations,
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speeding up commands like `git log`.
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* *Multi-pack-index:* enables fast object lookups across many pack-files.
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* *Incremental repack:* Repacks the packed Git data into fewer pack-file
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without disrupting concurrent commands by using the multi-pack-index.
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By running `scalar register` in any Git repo, Scalar will automatically enable
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these features for that repo (except partial clone) and start running suggested
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maintenance in the background using
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[the `git maintenance` feature](https://git-scm.com/docs/git-maintenance).
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Repos cloned with the `scalar clone` command use partial clone to significantly
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reduce the amount of data required to get started using a repository. By
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delaying all blob downloads until they are required, Scalar allows you to work
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with very large repositories quickly.
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Documentation
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-------------
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* [Getting Started](getting-started.md): Get started with Scalar.
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Includes `scalar register`, `scalar unregister`, `scalar clone`, and
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`scalar delete`.
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* [Troubleshooting](troubleshooting.md):
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Collect diagnostic information or update custom settings. Includes
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`scalar diagnose`.
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* [The Philosophy of Scalar](philosophy.md): Why does Scalar work the way
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it does, and how do we make decisions about its future?
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* [Frequently Asked Questions](faq.md)

‎contrib/scalar/docs/philosophy.md‎

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The Philosophy of Scalar
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========================
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The team building Scalar has **opinions** about Git performance. Scalar
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takes out the guesswork by automatically configuring your Git repositories
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to take advantage of the latest and greatest features. It is difficult to
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say that these are the absolute best settings for every repository, but
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these settings do work for some of the largest repositories in the world.
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Scalar intends to do very little more than the standard Git client. We
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actively implement new features into Git instead of Scalar, then update
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Scalar only to configure those new settings. In particular, we ported
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features like background maintenance to Git to make Scalar simpler and
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make Git more powerful.
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Services such as GitHub support partial clone , a standard adopted by the Git
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project to download only part of the Git objects when cloning, and fetching
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further objects on demand. If your hosting service supports partial clone, then
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we absolutely recommend it as a way to greatly speed up your clone and fetch
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times and to reduce how much disk space your Git repository requires. Scalar
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will help with this!
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Most of the value of Scalar can be found in the core Git client. However, most
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of the advanced features that really optimize Git's performance are off by
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default for compatibility reasons. To really take advantage of Git's latest and
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greatest features, you either need to study the [`git config`
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documentation](https://git-scm.com/docs/git-config) and regularly read [the Git
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release notes](https://github.com/git/git/tree/master/Documentation/RelNotes).
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Even if you do all that work and customize your Git settings on your machines,
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you likely will want to share those settings with other team members. Or, you
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can just use Scalar!
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Using `scalar register` on an existing Git repository will give you these
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benefits:
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* Additional compression of your `.git/index` file.
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* Hourly background `git fetch` operations, keeping you in-sync with your
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remotes.
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* Advanced data structures, such as the `commit-graph` and `multi-pack-index`
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are updated automatically in the background.
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* If using macOS or Windows, then Scalar configures Git's builtin File System
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Monitor, providing faster commands such as `git status` or `git add`.
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Additionally, if you use `scalar clone` to create a new repository, then
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you will automatically get these benefits:
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* Use Git's partial clone feature to only download the files you need for
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your current checkout.
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* Use Git's [sparse-checkout feature][sparse-checkout] to minimize the
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number of files required in your working directory.
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[Read more about sparse-checkout here.][sparse-checkout-blog]
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* Create the Git repository inside `<repo-name>/src` to make it easy to
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place build artifacts outside of the Git repository, such as in
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`<repo-name>/bin` or `<repo-name>/packages`.
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We also admit that these **opinions** can always be improved! If you have
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an idea of how to improve our setup, consider
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[creating an issue](https://github.com/microsoft/scalar/issues/new) or
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contributing a pull request! Some [existing](https://github.com/microsoft/scalar/issues/382)
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[issues](https://github.com/microsoft/scalar/issues/388) have already
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improved our configuration settings and roadmap!
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[gvfs-protocol]: https://github.com/microsoft/VFSForGit/blob/HEAD/Protocol.md
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[microsoft-git]: https://github.com/microsoft/git
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[sparse-checkout]: https://git-scm.com/docs/git-sparse-checkout
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[sparse-checkout-blog]: https://github.blog/2020-01-17-bring-your-monorepo-down-to-size-with-sparse-checkout/

‎contrib/scalar/docs/troubleshooting.md‎

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Troubleshooting
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===============
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Diagnosing Issues
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-----------------
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The `scalar diagnose` command collects logs and config details for the current
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repository. The resulting zip file helps root-cause issues.
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When run inside your repository, creates a zip file containing several important
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files for that repository. This includes:
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* Configuration files from your `.git` folder, such as the `config` file,
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`index`, `hooks`, and `refs`.
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* A summary of your Git object database, including the number of loose objects
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and the names and sizes of pack-files.
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As the `diagnose` command completes, it provides the path of the resulting
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zip file. This zip can be attached to bug reports to make the analysis easier.

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