Optimize git library installation

src/haxelib/VersionData.hx

@@ -19,6 +19,13 @@ package haxelib;
 		else
 			throw 'Invalid VscID $s';
 	}
+
+	public function getName() {
+		return switch cast(this, VcsID) {
+			case Git: "Git";
+			case Hg: "Mercurial";
+		};
+	}
 }
 
 /** Class containing repoducible git or hg library data. **/
@@ -28,7 +35,7 @@ class VcsData {
 	var url:String;
 	/** Commit hash **/
 	@:optional
-	var ref:Null<String>;
+	var commit:Null<String>;
 	/** The git tag or mercurial revision **/
 	@:optional
 	var tag:Null<String>;
@@ -45,7 +52,7 @@ class VcsData {
 
 	public function toString(): String {
 		var qualifier =
-			if (ref != null) ref
+			if (commit != null) commit
 			else if (tag != null) tag
 			else if (branch != null) branch
 			else null;
@@ -54,6 +61,39 @@ class VcsData {
 		else
 			url;
 	}
+
+	/**
+		Returns whether this vcs data will always reproduce an identical installation
+		(i.e. the commit id is locked down)
+	**/
+	public function isReproducible() {
+		return commit != null;
+	}
+
+	/**
+		Returns an anonymous object containing only the non-null, non-empty VcsData fields,
+		excluding the null/empty ones.
+	 **/
+	public function getCleaned() {
+		var data:{
+			url:String,
+			?commit:String,
+			?tag:String,
+			?branch:String,
+			?subDir:String
+		} = { url : url };
+
+		if (commit != null)
+			data.commit = commit;
+		if (tag != null)
+			data.tag = tag;
+		if (!(branch == null || branch == ""))
+			data.branch = branch;
+		if (!(subDir == null || haxe.io.Path.normalize(subDir) == ""))
+			data.subDir = subDir;
+
+		return data;
+	}
 }
 
 /** Data required to reproduce a library version **/
@@ -89,7 +129,7 @@ class VersionDataHelper {
 			type: type,
 			data: {
 				url: vcsRegex.matched(2),
-				ref: vcsRegex.matched(3),
+				commit: vcsRegex.matched(3),
 				branch: vcsRegex.matched(4),
 				subDir: null,
 				tag: null

src/haxelib/api/FsUtils.hx

@@ -216,4 +216,21 @@ class FsUtils {
 		seek(root);
 		return ret;
 	}
+
+    /**
+        Switches to directory found at `path`, executes `f()` in this directory,
+        before switching back to the previous directory.
+    **/
+    public static function runInDirectory<T>(path:String, f:() -> T):T {
+        final oldCwd = Sys.getCwd();
+        try {
+            Sys.setCwd(path);
+            final value = f();
+            Sys.setCwd(oldCwd);
+            return value;
+        } catch (e) {
+            Sys.setCwd(oldCwd);
+            throw e;
+        }
+    }
 }

src/haxelib/api/GlobalScope.hx

@@ -59,9 +59,11 @@ class GlobalScope extends Scope {
 	}
 
 	public function setVcsVersion(library:ProjectName, vcsVersion:VcsID, ?data:VcsData):Void {
-		if (data == null) data = {url: "unknown"};
+		if (data != null) {
+			repository.setVcsData(library, vcsVersion, data);
+		}
 
-		if (data.subDir != null) {
+		if (data != null && data.subDir != "" && data.subDir != null) {
 			final devDir = repository.getValidVersionPath(library, vcsVersion) + data.subDir;
 			repository.setDevPath(library, devDir);
 		} else {
@@ -273,4 +275,15 @@ class GlobalScope extends Scope {
 		return {path: path, version: current};
 	}
 
+	public function resolve(library:ProjectName):VersionData {
+		final version = repository.getCurrentVersion(library);
+
+		return switch version {
+			case vcs if (VcsID.isValid(vcs)):
+				final vcsId = VcsID.ofString(vcs);
+				VcsInstall(vcsId, repository.getVcsData(library, vcsId));
+			case semVer:
+				Haxelib(SemVer.ofString(semVer));
+		};
+	}
 }