[update-checkout] add a README

Author: charles-zablit

utils/update_checkout/README.md

@@ -0,0 +1,99 @@
+# update-checkout
+
+`update-checkout` is Swift's multi repository management tool. It allows to clone and update all the required repositories to build the Swift toolchain based on the `update-checkout-config.json` configuration file.
+
+## Installation
+
+`update-checkout` does not have any dependencies apart from `Python 3.7` or more recent. To run it, clone the `swift` repository and run the following command to print the help output:
+
+```bash
+./swift/utils/update-checkout -h
+```
+
+## Usage
+
+The following commands assume you have a working `Python 3` installation and that you have already cloned the `swift` repository.
+
+### Cloning the repositories and checking out a specific scheme
+
+To clone the repositories for the `release/6.2` scheme, run the following command:
+
+```bash
+./swift/utils/update-checkout --clone --scheme release/6.2
+```
+
+The command above will use `HTTPS` to clone the repositories. Use `--clone-with-ssh` to clone with `SSH` instead:
+
+```bash
+./swift/utils/update-checkout --clone-with-ssh --scheme release/6.2
+```
+
+You can skip repositories by adding the `--skip-repository` argument:
+
+```bash
+./swift/utils/update-checkout --clone-with-ssh --scheme release/6.2 --skip-repository llvm-project --skip-repository swift
+```
+
+### Updating or switching between schemes
+
+To update all the repositories after they have been cloned or to switch to another scheme, run:
+
+```bash
+./swift/utils/update-checkout --scheme main
+```
+
+If you have changes in any of the repositories, you can stash or clean them before updating. Please refer to the `help` for the details as to how `--clean` and `--stash` differ.
+
+```bash
+./swift/utils/update-checkout --scheme main --clean
+```
+
+### Resetting all repositories to the remote state
+
+To reset the branches from each repositories to the state of the matching remote branch, run the following command:
+
+```bash
+./swift/utils/update-checkout --reset-to-remote --scheme release/6.2
+```
+
+To reset the branches to a tag rather than a scheme, run:
+
+```bash
+./swift/utils/update-checkout --reset-to-remote --tag swift-6.2.1-RELEASE
+```
+
+You can skip repositories by adding the `--skip-repository` argument:
+
+```bash
+./swift/utils/update-checkout --reset-to-remote --scheme release/6.2 --skip-repository llvm-project --skip-repository swift
+```
+
+### Matching timestamps
+
+To checkout the commits that most closely match the timestamp of the checked out commit of the Swift repository, run:
+
+```bash
+./swift/utils/update-checkout --scheme release/6.2 --match-timestamp
+```
+
+## Testing
+
+`update-checkout` has both unit and end to end tests located in the `tests` directory. You can run them with the following command:
+
+```bash
+python3 ./swift/utils/update_checkout/run_tests.py
+```
+
+The tests are also part of the `check-swift` target, which means they run on CI along the other Swift tests.
+
+## Contributing
+
+Before contributing, please read [our main guide](https://www.swift.org/contributing)
+
+## LICENSE
+
+See [LICENSE](../../LICENSE.txt) for license information.
+
+## Code of Conduct
+
+See [Swift.org Code of Conduct](https://swift.org/code-of-conduct/) for Code of Conduct information.

utils/update_checkout/update_checkout/cli_arguments.py

@@ -37,7 +37,7 @@ def parse_args() -> "CliArguments":
         )
         parser.add_argument(
             "--clone",
-            help="obtain sources for Swift and related projects",
+            help="Obtain sources for Swift and related projects",
             action="store_true",
         )
         parser.add_argument(