Support for specifying a branch for a dependency.

Sources/Get/Fetchable.swift

@@ -12,7 +12,7 @@ import struct PackageDescription.Version
 
 protocol Fetchable {
     var version: Version { get }
-    var children: [(String, Range<Version>)] { get }
+    var children: [(String, String, Range<Version>)] { get }
 
     /**
      This should be a separate protocol. But Swift 2 was not happy

Sources/Get/Fetcher.swift

@@ -18,10 +18,10 @@ protocol Fetcher {
     associatedtype T: Fetchable
 
     func find(url url: String) throws -> Fetchable?
-    func fetch(url url: String) throws -> Fetchable
+	func fetch(url url: String, branch: String) throws -> Fetchable
     func finalize(fetchable: Fetchable) throws -> T
 
-    func recursivelyFetch(urls: [(String, Range<Version>)]) throws -> [T]
+    func recursivelyFetch(urls: [(String, String, Range<Version>)]) throws -> [T]
 }
 
 extension Fetcher {
@@ -30,13 +30,13 @@ extension Fetcher {
 
      This is our standard implementation that we override when testing.
      */
-    func recursivelyFetch(urls: [(String, Range<Version>)]) throws -> [T] {
+    func recursivelyFetch(urls: [(String, String, Range<Version>)]) throws -> [T] {
 
         var graph = [String: (Fetchable, Range<Version>)]()
 
-        func recurse(urls: [(String, Range<Version>)]) throws -> [String] {
+        func recurse(urls: [(String, String, Range<Version>)]) throws -> [String] {
 
-            return try urls.flatMap { url, specifiedVersionRange -> [String] in
+            return try urls.flatMap { url, branch, specifiedVersionRange -> [String] in
 
                 func adjust(pkg: Fetchable, _ versionRange: Range<Version>) throws {
                     guard let v = pkg.constrain(to: versionRange) else {
@@ -89,7 +89,7 @@ extension Fetcher {
 
                     // clone the package
 
-                    let clone = try self.fetch(url: url)
+					let clone = try self.fetch(url: url, branch: branch)
                     try adjust(clone, specifiedVersionRange)
                     graph[url] = (clone, specifiedVersionRange)
                     return try recurse(clone.children) + [url]

Sources/Get/Git.swift

@@ -15,7 +15,7 @@ import enum POSIX.Error
 import Utility
 
 extension Git {
-    class func clone(url: String, to dstdir: String) throws -> Repo {
+	class func clone(url: String, branch: String, to dstdir: String) throws -> Repo {
         // canonicalize URL
         var url = url
         if URL.scheme(url) == nil {
@@ -34,7 +34,10 @@ extension Git {
             try system(Git.tool, "clone",
                        "--recursive",   // get submodules too so that developers can use these if they so choose
                 "--depth", "10",
-                url, dstdir, environment: environment, message: "Cloning \(url)")
+                "--branch", branch, "--single-branch",
+                url, dstdir,
+                environment: environment,
+                message: "Cloning \(url)" + (branch == "master" ? "" : " \(branch)"))
         } catch POSIX.Error.ExitStatus {
             // Git 2.0 or higher is required
             if Git.majorVersionNumber < 2 {

Sources/Get/Package.swift

@@ -25,8 +25,8 @@ extension Package {
 }
 
 extension Package: Fetchable {
-    var children: [(String, Range<Version>)] {
-        return manifest.package.dependencies.map{ ($0.url, $0.versionRange) }
+    var children: [(String, String, Range<Version>)] {
+		return manifest.package.dependencies.map{ ($0.url, $0.branch, $0.versionRange) }
     }
 
     private var versionString: String.CharacterView {

Sources/Get/PackagesDirectory.swift

@@ -39,15 +39,15 @@ extension PackagesDirectory: Fetcher {
         return nil
     }
 
-    func fetch(url url: String) throws -> Fetchable {
+	func fetch(url url: String, branch: String) throws -> Fetchable {
         let dstdir = Path.join(prefix, Package.nameForURL(url))
         if let repo = Git.Repo(path: dstdir) where repo.origin == url {
             //TODO need to canonicalize the URL need URL struct
             return try RawClone(path: dstdir, manifestParser: manifestParser)
         }
 
         // fetch as well, clone does not fetch all tags, only tags on the master branch
-        try Git.clone(url, to: dstdir).fetch()
+		try Git.clone(url, branch: branch, to: dstdir).fetch()
 
         return try RawClone(path: dstdir, manifestParser: manifestParser)
     }

Sources/Get/RawClone.swift

@@ -83,7 +83,7 @@ class RawClone: Fetchable {
         }.last
     }
 
-    var children: [(String, Range<Version>)] {
+    var children: [(String, String, Range<Version>)] {
         guard manifest != nil else {
             // manifest may not exist, if so the package is BAD,
             // still: we should not crash. Build failure will occur

Sources/Get/get().swift

@@ -43,7 +43,7 @@ public func get(manifest: Manifest, manifestParser: (path: String, url: String)
 import PackageDescription
 
 extension Manifest {
-    var dependencies: [(String, Range<Version>)] {
-        return package.dependencies.map{ ($0.url, $0.versionRange) }
+    var dependencies: [(String, String, Range<Version>)] {
+        return package.dependencies.map{ ($0.url, $0.branch, $0.versionRange) }
     }
 }

Sources/ManifestParser/fromTOML().swift

@@ -62,12 +62,13 @@ extension PackageDescription.Package {
 
 extension PackageDescription.Package.Dependency {
     public static func fromTOML(item: TOMLItem, baseURL: String?) -> PackageDescription.Package.Dependency {
-        guard case .Array(let array) = item where array.items.count == 3 else {
+        guard case .Array(let array) = item where array.items.count == 4 else {
             fatalError("Unexpected TOMLItem")
         }
         guard case .String(let url) = array.items[0],
-              case .String(let vv1) = array.items[1],
-              case .String(let vv2) = array.items[2],
+		      case .String(let branch) = array.items[1],
+              case .String(let vv1) = array.items[2],
+              case .String(let vv2) = array.items[3],
               let v1 = Version(vv1), v2 = Version(vv2)
         else {
             fatalError("Unexpected TOMLItem")
@@ -81,7 +82,7 @@ extension PackageDescription.Package.Dependency {
             }
         }
 
-        return PackageDescription.Package.Dependency.Package(url: fixURL(), versions: v1..<v2)
+		return PackageDescription.Package.Dependency.Package(url: fixURL(), branch: branch, versions: v1..<v2)
     }
 }
 

Sources/PackageDescription/Package.swift

@@ -20,23 +20,25 @@ public final class Package {
     public class Dependency {
         public let versionRange: Range<Version>
         public let url: String
+		public let branch: String
 
-        init(_ url: String, _ versionRange: Range<Version>) {
+		init(_ url: String, _ branch: String, _ versionRange: Range<Version>) {
             self.url = url
+			self.branch = branch
             self.versionRange = versionRange
         }
 
-        public class func Package(url url: String, versions: Range<Version>) -> Dependency {
-            return Dependency(url, versions)
+		public class func Package(url url: String, branch: String = "master", versions: Range<Version>) -> Dependency {
+            return Dependency(url, branch, versions)
         }
-        public class func Package(url url: String, majorVersion: Int) -> Dependency {
-            return Dependency(url, Version(majorVersion, 0, 0)..<Version(majorVersion, .max, .max))
+        public class func Package(url url: String, branch: String = "master", majorVersion: Int) -> Dependency {
+            return Dependency(url, branch, Version(majorVersion, 0, 0)..<Version(majorVersion, .max, .max))
         }
-        public class func Package(url url: String, majorVersion: Int, minor: Int) -> Dependency {
-            return Dependency(url, Version(majorVersion, minor, 0)..<Version(majorVersion, minor, .max))
+        public class func Package(url url: String, branch: String = "master", majorVersion: Int, minor: Int) -> Dependency {
+            return Dependency(url, branch, Version(majorVersion, minor, 0)..<Version(majorVersion, minor, .max))
         }
-        public class func Package(url url: String, _ version: Version) -> Dependency {
-            return Dependency(url, version...version)
+        public class func Package(url url: String, branch: String = "master", _ version: Version) -> Dependency {
+            return Dependency(url, branch, version...version)
         }
     }
 
@@ -80,7 +82,7 @@ public final class Package {
 
 extension Package.Dependency: TOMLConvertible {
     public func toTOML() -> String {
-        return "[\"\(url)\", \"\(versionRange.startIndex)\", \"\(versionRange.endIndex)\"],"
+        return "[\"\(url)\", \"\(branch)\", \"\(versionRange.startIndex)\", \"\(versionRange.endIndex)\"],"
     }
 }