Update README.md to reflect the current feature set (#90)

Xcode 12 warning is removed as 5.3 SwiftWasm snapshots that became the default are compatible with Xcode 12.

Closes #65.
Closes #81.

README.md

@@ -5,7 +5,7 @@
 The main goal of `carton` is to provide a smooth zero-config experience when developing for WebAssembly.
 It is still in development, but it aims to support these features (🐥 means "ready to use"):
 
-- 🥚 Creating basic package boilerplate for apps built with SwiftWasm with `carton init`.
+- 🐥 Creating basic package boilerplate for apps built with SwiftWasm with `carton init`.
 - 🐥 Watching the app for source code changes and reloading it in your browser with `carton dev`.
 - 🐣 Running your XCTest suite in the full JavaScript/DOM environment with `carton test`.
 - 🥚 Optimizing and packaging the app for distribution with `carton bundle`.
@@ -21,15 +21,14 @@ trying to make its config file work, looking for appropriate plugins. I'm convin
 you can avoid using `webpack` altogether. `carton` also simplifies a few other things in your SwiftWasm
 development workflow such as toolchain and SDK installations.
 
-## Requirements
+## Getting started
 
-- macOS 10.15 and Xcode 11.4/11.5/11.6 for macOS. Xcode betas are currently not supported. You can have
-  those installed, but please make sure you use
-  [`xcode-select`](https://developer.apple.com/library/archive/technotes/tn2339/_index.html#//apple_ref/doc/uid/DTS40014588-CH1-HOW_DO_I_SELECT_THE_DEFAULT_VERSION_OF_XCODE_TO_USE_FOR_MY_COMMAND_LINE_TOOLS_)
-  to point it to a release version of Xcode.
+### Requirements
+
+- macOS 10.15 and Xcode 11.4 or later.
 - [Swift 5.2 or later](https://swift.org/download/) for Linux users.
 
-## Installation
+### Installation
 
 On macOS `carton` can be installed with [Homebrew](https://brew.sh/). Make sure you have Homebrew
 installed and then run:
@@ -42,12 +41,38 @@ You'll have to build `carton` from sources on Linux. Clone the repository and ru
 `swift build -c release`, the `carton` binary will be located in the `.build/release/carton`
 directory after that.
 
-`carton` automatically installs the required SwiftWasm toolchain and SDK when you build
-your project with `carton dev`. You can however install SwiftWasm separately if needed,
-either by passing an archive URL to `carton sdk install` directly, or just specifying the snapshot
-version, like `carton sdk install wasm-5.3-SNAPSHOT-2020-08-15-a`. `carton dev` can
-also detect existing installations of `swiftenv`, so if you already have SwiftWasm installed
-via `swiftenv`, you don't have to do anything on top of that to start using `carton`.
+### Usage
+
+The `carton init` command initializes a new SwiftWasm project for you (similarly to `swift package init`) with multiple templates available at your choice. `carton init --template tokamak` creates a
+new [Tokamak](https://tokamak.dev/) project, while `carton init --template basic` (equivalent to
+`carton init`) creates an empty SwiftWasm project with no dependencies. Also, `carton init list-templates` provides a complete list of templates (with only `basic` and `tokamak` available
+currently).
+
+The `carton dev` command builds your project with the SwiftWasm toolchain and starts an HTTP server
+that hosts your WebAssembly executable and a corresponding JavaScript entrypoint that loads it. Open
+[http://127.0.0.1:8080/](http://127.0.0.1:8080/) in your browser to see the app running. You can
+edit the app source code in your favorite editor and save it, `carton` will immediately rebuild the
+app and reload all browser tabs that have the app open. You can also pass a `--verbose` flag to
+keep the build process output available, otherwise stale output is cleaned up from your terminal
+screen by default.
+
+The `carton test` command runs your test suite in the [`wasmer`](https://wasmer.io/) environment.
+Unfortunately, this currently requires a presence of `LinuxMain.swift` file and explicit test
+manifests, `--enable-test-discovery` flag is not supported yet. Projects that can build their test
+suite on macOS can use `swift test --generate-linuxmain` command to generate this file.
+
+The `carton sdk` command and its subcommands allow you to manage installed SwiftWasm toolchains, but
+is rarely needed, as `carton dev` install the recommended version of SwiftWasm automatically.
+`carton sdk versions` lists all installed versions, and `carton sdk local` prints the version
+specified for the current project in the `.swift-version` file. You can however install SwiftWasm
+separately if needed, either by passing an archive URL to `carton sdk install` directly, or just
+specifying the snapshot version, like `carton sdk install wasm-DEVELOPMENT-SNAPSHOT-2020-06-07-a`.
+
+`carton dev` can also detect existing installations of `swiftenv`, so if you already have SwiftWasm
+installed via `swiftenv`, you don't have to do anything on top of that to start using `carton`.
+
+All of these commands and subcommands can be passed a `--help` flag that prints usage info and
+information about all available options.
 
 ## How does it work?
 
@@ -80,12 +105,9 @@ browsers and receiving test results back to the HTTP server, so that test result
 This was blocked by [`XCTest` not allowing customized test report formats](https://bugs.swift.org/browse/SR-8436),
 which is now partially resolved with [a new argument available on
 `XCTMain`](https://github.com/apple/swift-corelibs-xctest/pull/306) and a custom [JSON test
-reporter](https://github.com/MaxDesiatov/XCTestJSONObserver/). After [a few other
-issues](https://github.com/swiftwasm/swift/pull/1233) are resolved with the SwiftWasm toolchain, I'll get
-`carton test` fully working with XCTest.
+reporter](https://github.com/MaxDesiatov/XCTestJSONObserver/).
 
-There are a few more commands on the roadmap to be implemented, such as `carton init` for initializing
-basic SwiftWasm projects (potentially with configurable templates), `carton bundle` to produce an
+There are a few more commands on the roadmap to be implemented, such as `carton bundle` to produce an
 optimized production deployment bundle, SwiftPM resources support for bundled assets, and much more.
 
 As cross-compiling to WebAssembly and running apps and tests remotely is not too dissimilar to Android