Implement blackbox in Golang (#250)

* Initial release

models/vcs.go

@@ -0,0 +1,30 @@
+package models
+
+import "github.com/StackExchange/blackbox/v2/pkg/commitlater"
+
+// Vcs is git/hg/etc.
+type Vcs interface {
+	// Name returns the plug-in's canonical name.
+	Name() string
+	// Discover returns true if we are a repo of this type; along with the Abs path to the repo root (or "" if we don't know).
+	Discover() (bool, string)
+
+	// SetFileTypeUnix informs the VCS that files should maintain unix-style line endings.
+	SetFileTypeUnix(repobasedir string, files ...string) error
+	// IgnoreAnywhere tells the VCS to ignore these files anywhere in the repo.
+	IgnoreAnywhere(repobasedir string, files []string) error
+	// IgnoreAnywhere tells the VCS to ignore these files, rooted in the base of the repo.
+	IgnoreFiles(repobasedir string, files []string) error
+
+	// CommitTitle sets the title of the next commit.
+	CommitTitle(title string)
+	// NeedsCommit queues up commits for later execution.
+	NeedsCommit(message string, repobasedir string, names []string)
+	// DebugCommits dumps a list of future commits.
+	DebugCommits() commitlater.List
+	// FlushCommits informs the VCS to do queued up commits.
+	FlushCommits() error
+
+	// TestingInitRepo initializes a repo of this type (for use by integration tests)
+	TestingInitRepo() error
+}