Update Package: Git-LFS (#1769)

* Fixed a few small bugs in the 'git-lfs' install script.

* Fixed a bug in the '(go|go-bootstrap)@1.4.2+test' install scripts.

* Fixing a minor style issue in the 'git-lfs' install script.

var/spack/repos/builtin/packages/git-lfs/package.py

@@ -26,17 +26,28 @@
 
 
 class GitLfs(Package):
-    """Tool for managing large files with Git."""
+    """Git LFS is a system for managing and versioning large files in
+       association with a Git repository.  Instead of storing the large files
+       within the Git repository as blobs, Git LFS stores special "pointer
+       files" in the repository, while storing the actual file contents on a
+       Git LFS server."""
 
     homepage = "https://git-lfs.github.com"
-    url      = "https://github.com/github/git-lfs/archive/v1.4.1.tar.gz"
+    git_url  = "https://github.com/github/git-lfs.git"
 
-    version('1.4.1', 'c62a314d96d3a30af4d98fa3305ad317')
+    version('1.4.1', git=git_url, tag='v1.4.1')
+    version('1.3.1', git=git_url, tag='v1.3.1')
+
+    # TODO: Implement this by following the instructions at this location:
+    # https://github.com/github/git-lfs/blob/master/CONTRIBUTING.md#building
+    # variant('test', default=True, description='Build and run tests as part of the build.')  # NOQA: E501
 
     depends_on('go@1.5:', type='build')
     depends_on('git@1.8.2:', type='run')
 
     def install(self, spec, prefix):
-        bootstrap = Executable('./scripts/bootstrap')
-        bootstrap()
-        install('bin/git-lfs', prefix.bin)
+        bootstrap_script = Executable(join_path('script', 'bootstrap'))
+        bootstrap_script()
+
+        mkdirp(prefix.bin)
+        install(join_path('bin', 'git-lfs'), prefix.bin)