✨ Allow for seamless upgrade to PHP 8.3

The older version (8.2 in most cases) that becomes obsolete will also
be reinstalled and the app will attempt to switch to the last active
version as well. It is likely that PHP Monitor will have to repair
your older PHP installations after upgrading the `php` formula, but
this too should be a seamless process.

phpmon/Common/PHP/PHP Version/PhpEnvironments.swift

@@ -29,7 +29,7 @@ class PhpEnvironments {
     /**
      Determine which PHP version the `php` formula is aliased to.
      */
-    func determinePhpAlias() async {
+    @MainActor func determinePhpAlias() async {
         let brewPhpAlias = await Shell.pipe("\(Paths.brew) info php --json").out
 
         self.homebrewPackage = try! JSONDecoder().decode(

phpmon/Domain/Integrations/Homebrew/BrewFormula.swift

@@ -54,6 +54,19 @@ struct BrewFormula: Equatable {
             && PhpEnvironments.homebrewBrewPhpAlias != PhpEnvironments.brewPhpAlias
     }
 
+    var unavailableAfterUpgrade: Bool {
+        if (installedVersion == nil || upgradeVersion == nil) {
+            return false
+        }
+
+        if let installed = try? VersionNumber.parse(self.installedVersion!),
+           let upgrade = try? VersionNumber.parse(self.upgradeVersion!) {
+            return upgrade.short != installed.short
+        }
+
+        return false
+    }
+
     /// The associated Homebrew folder with this PHP formula.
     var homebrewFolder: String {
         let resolved = name

phpmon/Domain/Integrations/Homebrew/Commands/InstallAndUpgradeCommand.swift

@@ -41,12 +41,22 @@ class InstallAndUpgradeCommand: BrewCommand {
             description: "PHP Monitor is preparing Homebrew..."
         ))
 
+        let unavailable = upgrading.first(where: { formula in
+            formula.unavailableAfterUpgrade
+        })
+
         // Make sure the tap is installed
         try await self.checkPhpTap(onProgress)
 
-        // Try to run all upgrade and installation operations
-        try await self.upgradePackages(onProgress)
-        try await self.installPackages(onProgress)
+        if unavailable == nil {
+            // Try to run all upgrade and installation operations
+            try await self.upgradePackages(onProgress)
+            try await self.installPackages(onProgress)
+        } else {
+            // Simply upgrade `php` to the latest version
+            try await self.upgradeMainPhpFormula(unavailable!, onProgress)
+            await PhpEnvironments.shared.determinePhpAlias()
+        }
 
         // Re-check the installed versions
         await PhpEnvironments.detectPhpVersions()
@@ -58,6 +68,27 @@ class InstallAndUpgradeCommand: BrewCommand {
         await self.completedOperations(onProgress)
     }
 
+    private func upgradeMainPhpFormula(
+        _ unavailable: BrewFormula,
+        _ onProgress: @escaping (BrewCommandProgress) -> Void
+    ) async throws {
+        // Determine which version was previously available (that will become unavailable)
+        guard let short = try? VersionNumber
+            .parse(unavailable.installedVersion!).short else {
+            return
+        }
+
+        // Upgrade the main formula
+        let command = """
+            export HOMEBREW_NO_INSTALL_CLEANUP=true; \
+            \(Paths.brew) upgrade php;
+            \(Paths.brew) install php@\(short);
+            """
+
+        // Run the upgrade command
+        try await run(command, onProgress)
+    }
+
     private func checkPhpTap(_ onProgress: @escaping (BrewCommandProgress) -> Void) async throws {
         if !BrewDiagnostics.installedTaps.contains("shivammathur/php") {
             let command = "brew tap shivammathur/php"