*: prepping for checking a diff

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

git/commits.go

@@ -58,6 +58,19 @@ var FieldNames = map[string]string{
 	"%G?": "verification_flag",
 }
 
+// Show returns the diff of a commit.
+//
+// NOTE: This could be expensive for very large commits.
+func Show(commit string) ([]byte, error) {
+	cmd := exec.Command("git", "show", commit)
+	cmd.Stderr = os.Stderr
+	out, err := cmd.Output()
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
 // CommitEntry represents a single commit's information from `git`.
 // See also FieldNames
 type CommitEntry map[string]string

rules/danglingwhitespace/rule.go

@@ -0,0 +1,26 @@
+package danglingwhitespace
+
+import (
+	"github.com/vbatts/git-validation/git"
+	"github.com/vbatts/git-validation/validate"
+)
+
+var (
+	// DanglingWhitespace is the rule for checking the presence of dangling
+	// whitespaces on line endings.
+	DanglingWhitespace = validate.Rule{
+		Name:        "dangling-whitespace",
+		Description: "checking the presence of dangling whitespaces on line endings",
+		Run:         ValidateDanglingWhitespace,
+	}
+)
+
+func init() {
+	validate.RegisterRule(DanglingWhitespace)
+}
+
+func ValidateDanglingWhitespace(c git.CommitEntry) (vr validate.Result) {
+	diff, err := git.Show(c["commit"])
+
+	return
+}