Prepare for the 0.4.0 release (#214)

Bump version to the 0.4.0 release and add upgrade routine from 0.4.0-dev.
Upate the github workflow default for making a release from main branch.

.github/workflows/build_release.yml

@@ -7,7 +7,7 @@ on:
         description: "Version of swiftly to build release artifacts"
         required: true
         type: string
-        default: "0.4.0-dev"
+        default: "0.4.0"
       skip:
         description: "Perform release checks, such as the git tag, and swift version, or '--skip' to skip that."
         required: true

Sources/Swiftly/Init.swift

@@ -37,8 +37,22 @@ internal struct Init: SwiftlyCommand {
 
         var config = try? Config.load()
 
+        if var config, !overwrite && config.version == SwiftlyVersion(major: 0, minor: 4, patch: 0, suffix: "dev") {
+            // This is a simple upgrade from the 0.4.0-dev pre-release
+
+            // Move our executable over to the correct place
+            try Swiftly.currentPlatform.installSwiftlyBin()
+
+            // Update and save the version
+            config.version = SwiftlyCore.version
+
+            try config.save()
+
+            return
+        }
+
         if let config, !overwrite && config.version != SwiftlyCore.version {
-            // We don't support downgrades, and we don't yet support upgrades
+            // We don't support downgrades, and versions prior to 0.4.0-dev
             throw SwiftlyError(message: "An existing swiftly installation was detected. You can try again with '--overwrite' to overwrite it.")
         }
 

Sources/SwiftlyCore/SwiftlyCore.swift

@@ -1,6 +1,6 @@
 import Foundation
 
-public let version = SwiftlyVersion(major: 0, minor: 4, patch: 0, suffix: "dev")
+public let version = SwiftlyVersion(major: 0, minor: 4, patch: 0)
 
 /// A separate home directory to use for testing purposes. This overrides swiftly's default
 /// home directory location logic.