Closes #43: Detect when tool not installed

Author: mattfarina

bzr.go

@@ -16,6 +16,10 @@ var bzrDetectURL = regexp.MustCompile("parent branch: (?P<foo>.+)\n")
 // NewBzrRepo creates a new instance of BzrRepo. The remote and local directories
 // need to be passed in.
 func NewBzrRepo(remote, local string) (*BzrRepo, error) {
+	ins := depInstalled("bzr")
+	if !ins {
+		return nil, NewLocalError("bzr is not installed", nil, "")
+	}
 	ltype, err := DetectVcsFromFS(local)
 
 	// Found a VCS other than Bzr. Need to report an error.

git.go

@@ -14,6 +14,10 @@ import (
 // NewGitRepo creates a new instance of GitRepo. The remote and local directories
 // need to be passed in.
 func NewGitRepo(remote, local string) (*GitRepo, error) {
+	ins := depInstalled("git")
+	if !ins {
+		return nil, NewLocalError("git is not installed", nil, "")
+	}
 	ltype, err := DetectVcsFromFS(local)
 
 	// Found a VCS other than Git. Need to report an error.

hg.go

@@ -14,6 +14,10 @@ var hgDetectURL = regexp.MustCompile("default = (?P<foo>.+)\n")
 // NewHgRepo creates a new instance of HgRepo. The remote and local directories
 // need to be passed in.
 func NewHgRepo(remote, local string) (*HgRepo, error) {
+	ins := depInstalled("hg")
+	if !ins {
+		return nil, NewLocalError("hg is not installed", nil, "")
+	}
 	ltype, err := DetectVcsFromFS(local)
 
 	// Found a VCS other than Hg. Need to report an error.

repo.go

@@ -257,3 +257,11 @@ NextVar:
 	}
 	return out
 }
+
+func depInstalled(name string) bool {
+	if _, err := exec.LookPath(name); err != nil {
+		return false
+	}
+
+	return true
+}

repo_test.go

@@ -60,3 +60,15 @@ func TestTypeSwitch(t *testing.T) {
 		t.Errorf("Not detecting repo switch from SVN to Git")
 	}
 }
+
+func TestDepInstalled(t *testing.T) {
+	i := depInstalled("git")
+	if i != true {
+		t.Error("depInstalled not finding installed dep.")
+	}
+
+	i = depInstalled("thisreallyisntinstalled")
+	if i != false {
+		t.Error("depInstalled finding not installed dep.")
+	}
+}

svn.go

@@ -15,6 +15,10 @@ import (
 // For example, if the package is https://github.com/Masterminds/cookoo/ the remote
 // should be https://github.com/Masterminds/cookoo/trunk for the trunk branch.
 func NewSvnRepo(remote, local string) (*SvnRepo, error) {
+	ins := depInstalled("svn")
+	if !ins {
+		return nil, NewLocalError("svn is not installed", nil, "")
+	}
 	ltype, err := DetectVcsFromFS(local)
 
 	// Found a VCS other than Svn. Need to report an error.