Removes old Sparkle updates that weren't removed properly.

SparkleCleanup.swift

import Foundation

struct SparkleCleanup {

    private static let oldDownloadAge: TimeInterval = 86400 // 24 hours

    /// The location where Sparkle caches file downloads.
    private static var cacheURL: URL {
        guard let bundleIdentifier = Bundle.main.bundleIdentifier else {
            fatalError("Unable to get bundle identifier.")
        }

        let path = "\(NSHomeDirectory())/Library/Caches/\(bundleIdentifier)/Sparkle"
        return URL(fileURLWithPath: path)
    }

    /// Downloaded updates that Sparkle failed to trash.
    private static var filesToRemove: [URL] {
        let toRemove = try? FileManager.default.contentsOfDirectory(
            at: cacheURL,
            includingPropertiesForKeys: [URLResourceKey.creationDateKey],
            options: [.skipsHiddenFiles]
        ).filter { url in
            let resourceValues = try? (url as NSURL).resourceValues(forKeys: [URLResourceKey.creationDateKey])

            guard let creationDate = resourceValues?[URLResourceKey.creationDateKey] as? NSDate else {
                // Leave the file alone if it lacks a creation date.
                return false
            }

            // Skip versions created in last 24 hours.
            return creationDate.timeIntervalSinceNow < -oldDownloadAge
        }

        return toRemove ?? []
    }

    /// Removes old versions that are kept around for whatever reason.
    static func removeOldVersions() {
        // Run task in the background so that it doesn't hold up the program.
        DispatchQueue.global(qos: .background).async {
            for url in self.filesToRemove {
                _ = try? FileManager.default.removeItem(at: url)
            }
        }
    }
}

No longer necessary as of Sparkle v1.15.0.