feat: Begin working on configuration client.

Sources/CliClient/Internal/VersionStrategy+currentVersion.swift

@@ -0,0 +1,103 @@
+import Dependencies
+import FileClient
+import struct Foundation.URL
+import GitClient
+
+@_spi(Internal)
+public extension CliClient.PreReleaseStrategy {
+
+  func preReleaseString(gitDirectory: String?) async throws -> String {
+    @Dependency(\.gitClient) var gitClient
+    switch self {
+    case let .custom(string, child):
+      guard let child else { return string }
+      return try await "\(string)-\(child.preReleaseString(gitDirectory: gitDirectory))"
+    case .tag:
+      return try await gitClient.version(.init(
+        gitDirectory: gitDirectory,
+        style: .tag(exactMatch: false)
+      )).description
+    case .branchAndCommit:
+      return try await gitClient.version(.init(
+        gitDirectory: gitDirectory,
+        style: .branch(commitSha: true)
+      )).description
+    }
+  }
+}
+
+@_spi(Internal)
+public extension CliClient.VersionStrategy.SemVarOptions {
+
+  private func applyingPreRelease(_ semVar: SemVar, _ gitDirectory: String?) async throws -> SemVar {
+    guard let preReleaseStrategy else { return semVar }
+    let preRelease = try await preReleaseStrategy.preReleaseString(gitDirectory: gitDirectory)
+    return semVar.applyingPreRelease(preRelease)
+  }
+
+  func currentVersion(file: URL, gitDirectory: String? = nil) async throws -> CurrentVersionContainer.Version {
+    @Dependency(\.fileClient) var fileClient
+    @Dependency(\.gitClient) var gitClient
+
+    let fileOutput = try? await fileClient.semVar(file: file, gitDirectory: gitDirectory)
+    var semVar = fileOutput?.semVar
+    let usesOptionalType = fileOutput?.usesOptionalType
+
+    if requireExistingFile {
+      guard let semVar else {
+        throw CliClientError.fileDoesNotExist(path: file.cleanFilePath)
+      }
+      return try await .semVar(
+        applyingPreRelease(semVar, gitDirectory),
+        usesOptionalType: usesOptionalType ?? false
+      )
+    }
+
+    // Didn't have existing semVar loaded from file, so check for git-tag.
+
+    semVar = try await gitClient.version(.init(
+      gitDirectory: gitDirectory,
+      style: .tag(exactMatch: false)
+    )).semVar
+    if requireExistingSemVar {
+      guard let semVar else {
+        fatalError()
+      }
+      return try await .semVar(
+        applyingPreRelease(semVar, gitDirectory),
+        usesOptionalType: usesOptionalType ?? false
+      )
+    }
+
+    return try await .semVar(
+      applyingPreRelease(.init(), gitDirectory),
+      usesOptionalType: usesOptionalType ?? false
+    )
+  }
+}
+
+@_spi(Internal)
+public extension CliClient.VersionStrategy {
+
+  func currentVersion(file: URL, gitDirectory: String?) async throws -> CurrentVersionContainer {
+    @Dependency(\.gitClient) var gitClient
+
+    switch self {
+    case .branchAndCommit:
+      return try await .init(
+        targetUrl: file,
+        version: .string(
+          gitClient.version(.init(
+            gitDirectory: gitDirectory,
+            style: .branch(commitSha: true)
+          )).description
+        )
+      )
+    case let .semVar(options):
+      return try await .init(
+        targetUrl: file,
+        version: options.currentVersion(file: file, gitDirectory: gitDirectory)
+      )
+    }
+  }
+}