This hack did not work in fact

Tweaks

.github/deploy

@@ -114,8 +114,10 @@ var defaultSwiftVersion: String {
 
 func podspec(repo: Repo, user: User, pkg: Package) -> (Substring, String) {
     let (owner, name) = { ($0[0], $0[1]) }(slug.split(separator: "/"))
-    let swiftVersion = pkg.swiftLanguageVersions.max() ?? defaultSwiftVersion
+    let swiftVersion = pkg.swiftLanguageVersions.min() ?? defaultSwiftVersion
-    let sources = pkg.targets.filter{ $0.type == .regular }.compactMap{ $0.path }.first!
+    let targets = pkg.targets.filter{ $0.type == .regular }
+    guard targets.count == 1 else { fatal(message: "Too many targets for this script!") }
+    guard let sources = targets[0].path else { fatal(message: "Target has no path!") }
     return (name, """
     Pod::Spec.new do |s|
       s.name = '\(name)'

.travis.yml

@@ -80,4 +80,4 @@ jobs:
       install: brew install mxcl/made/swift-sh
       before_script: .github/deploy generate-podspec
       script: pod trunk push
-      after_success: .github/deploy post-release
+      after_success: .github/deploy publish-release

Package.swift

@@ -1,7 +1,7 @@
 // swift-tools-version:4.2
 import PackageDescription
 
-let package = Package(
+let pkg = Package(
     name: "Path.swift",
     products: [
         .library(name: "Path", targets: ["Path"]),
@@ -9,5 +9,6 @@ let package = Package(
     targets: [
         .target(name: "Path", path: "Sources"),
         .testTarget(name: "PathTests", dependencies: ["Path"]),
-    ]
+    ],
+    swiftLanguageVersions: [.v4, .v4_2]
 )

Package@swift-5.0.swift

@@ -9,9 +9,6 @@ let pkg = Package(
     targets: [
         .target(name: "Path", path: "Sources"),
         .testTarget(name: "PathTests", dependencies: ["Path"]),
-    ]
+    ],
+    swiftLanguageVersions: [.v4, .v4_2, .v5]
 )
-
-pkg.swiftLanguageVersions = [
-    .v4_2, .v5
-]