Improved Describe.String()

Signed-off-by: Eduardo Lezcano <eduardo.lezcano@be.atlascopco.com>

options.go

@@ -446,7 +446,7 @@ type DescribeOptions struct {
 	//FirstParent bool
 	// Use <Abbrev> digits to display SHA-1s
 	// By default is 8
-	//Abbrev int
+	Abbrev int
 	// Only output exact matches
 	//ExactMatch bool
 	// Consider <Candidates> most recent tags
@@ -460,4 +460,6 @@ type DescribeOptions struct {
 	Dirty string
 }
 
-func (o *DescribeOptions) Validate() error { return nil }
+func (o *DescribeOptions) Validate() error {
+	if o.Abbrev == 0 { o.Abbrev = 8 }
+	return nil }

repository.go

@@ -1233,14 +1233,25 @@ type Describe struct {
 	Distance int
 	// Dirty string to append
 	Dirty string
+	// Use <Abbrev> digits to display SHA-ls
+	Abbrev int
 }
 
 func (d *Describe) String() string {
-	return fmt.Sprintf("%v-%v-%v-%v",
-		d.Tag.Name().Short(),
-		d.Distance,
-		d.Reference.Hash().String()[0:8],
-		d.Dirty)
+	var s []string
+
+	if d.Tag != nil{
+		s = append(s, d.Tag.Name().Short())
+	}
+	if d.Distance > 0 {
+		s = append(s, fmt.Sprint(d.Distance))
+	}
+	s = append(s, d.Reference.Hash().String()[0:d.Abbrev])
+	if d.Dirty != "" {
+		s = append(s, d.Dirty)
+	}
+
+	return strings.Join(s, "-")
 }
 
 // Describe just like the `git describe` command will return a Describe struct for the hash passed.
@@ -1290,6 +1301,7 @@ func (r *Repository) Describe(ref *plumbing.Reference, opts *DescribeOptions) (*
 		tag,
 		count,
 		opts.Dirty,
+		opts.Abbrev,
 	}, nil
 
 }