Update Git type for ProcessEnvironmentBlock (#470)

Previous implementation did not account for case insensitivity on Windows and made it hard to remove deprecation warnings in clients of TSC.

Author: MaxDesiatov

Sources/TSCUtility/Git.swift

@@ -11,51 +11,7 @@
 import class Foundation.ProcessInfo
 import TSCBasic
 
-extension Version {
-    // FIXME: deprecate 2/2021 (used below), remove once clients transitioned
-    @available(*, deprecated, message: "moved to SwiftPM")
-    init?(tag: String) {
-        if tag.first == "v" {
-            self.init(string: String(tag.dropFirst()))
-        } else {
-            self.init(string: tag)
-        }
-    }
-}
-
 public enum Git {
-    // FIXME: deprecate 2/2021, remove once clients transitioned
-    @available(*, deprecated, message: "moved to SwiftPM")
-    public static func convertTagsToVersionMap(_ tags: [String]) -> [Version: [String]] {
-        // First, check if we need to restrict the tag set to version-specific tags.
-        var knownVersions: [Version: [String]] = [:]
-        var versionSpecificKnownVersions: [Version: [String]] = [:]
-
-        for tag in tags {
-            for versionSpecificKey in Versioning.currentVersionSpecificKeys {
-                if tag.hasSuffix(versionSpecificKey) {
-                    let trimmedTag = String(tag.dropLast(versionSpecificKey.count))
-                    if let version = Version(tag: trimmedTag) {
-                        versionSpecificKnownVersions[version, default: []].append(tag)
-                    }
-                    break
-                }
-            }
-            
-            if let version = Version(tag: tag) {
-                knownVersions[version, default: []].append(tag)
-            }
-        }
-        // Check if any version specific tags were found.
-        // If true, then return the version specific tags,
-        // or else return the version independent tags.
-        if !versionSpecificKnownVersions.isEmpty {
-            return versionSpecificKnownVersions
-        } else {
-            return knownVersions
-        }
-    }
-
     /// A shell command to run for Git. Can be either a name or a path.
     ///  - Note: modification is not thread safe, designed for testing only
     public static var tool: String = "git\(executableFileSuffix)"
@@ -70,20 +26,55 @@ public enum Git {
         }
     }
 
-    private static var _gitEnvironment = ProcessInfo.processInfo.environment
+    private static var _gitEnvironment = ProcessEnv.block
+
+    @available(*,
+        deprecated,
+        renamed: "environmentBlock",
+        message: "Previous `[String: String]` representation did not account for case insensitivity on Windows."
+    )
+    public static var environment: [String: String] {
+        get {
+            var env = Self._gitEnvironment
+
+            // These variables are inserted into the environment when shelling out
+            // to git if not already present.
+            let underrideVariables: ProcessEnvironmentBlock =  [
+                // Disable terminal prompts in git. This will make git error out and return
+                // when it needs a user/pass etc instead of hanging the terminal (SR-3981).
+                "GIT_TERMINAL_PROMPT": "0",
+
+                // The above is env variable is not enough. However, ssh_config's batch
+                // mode is made for this purpose. see: https://linux.die.net/man/5/ssh_config
+                "GIT_SSH_COMMAND": "ssh -oBatchMode=yes",
+            ]
+
+            for (key, value) in underrideVariables {
+                // Skip this key is already present in the env.
+                if env.keys.contains(key) { continue }
+
+                env[key] = value
+            }
+
+            return Dictionary(env.map { ($0.value, $1) }, uniquingKeysWith: { $1 })
+        }
+        set {
+            Self._gitEnvironment = .init(newValue)
+        }
+    }
 
     /// Returns the environment variables for launching the git subprocess.
     ///
     /// This contains the current environment with custom overrides for using
     /// git from swift build.
     ///  - Note: modification is not thread safe, designed for testing only
-    public static var environment: [String: String] {
+    public static var environmentBlock: ProcessEnvironmentBlock {
         get {
             var env = Self._gitEnvironment
 
             // These variables are inserted into the environment when shelling out
             // to git if not already present.
-            let underrideVariables =  [
+            let underrideVariables: ProcessEnvironmentBlock =  [
                 // Disable terminal prompts in git. This will make git error out and return
                 // when it needs a user/pass etc instead of hanging the terminal (SR-3981).
                 "GIT_TERMINAL_PROMPT": "0",