config: RefSpec.Validate returning errors and doc (Fixes #232)

1 files changed, 16 insertions, 6 deletions

diff --git a/config/refspec.go b/config/refspec.go
index dca0d82..dd68edc 100644
--- a/config/refspec.go
+++ b/config/refspec.go
@@ -1,6 +1,7 @@
 package config
 
 import (
+	"errors"
 	"strings"
 
 	"srcd.works/go-git.v4/plumbing"
@@ -12,6 +13,11 @@ const (
 	refSpecSeparator = ":"
 )
 
+var (
+	ErrRefSpecMalformedSeparator = errors.New("malformed refspec, separators are wrong")
+	ErrRefSpecMalformedWildcard  = errors.New("malformed refspec, missmatched number of wildcards")
+)
+
 // RefSpec is a mapping from local branches to remote references
 // The format of the refspec is an optional +, followed by <src>:<dst>, where
 // <src> is the pattern for references on the remote side and <dst> is where
@@ -22,21 +28,25 @@ const (
 // https://git-scm.com/book/es/v2/Git-Internals-The-Refspec
 type RefSpec string
 
-// IsValid validates the RefSpec
-func (s RefSpec) IsValid() bool {
+// Validate validates the RefSpec
+func (s RefSpec) Validate() error {
 	spec := string(s)
 	if strings.Count(spec, refSpecSeparator) != 1 {
-		return false
+		return ErrRefSpecMalformedSeparator
 	}
 
 	sep := strings.Index(spec, refSpecSeparator)
-	if sep == len(spec) {
-		return false
+	if sep == len(spec)-1 {
+		return ErrRefSpecMalformedSeparator
 	}
 
 	ws := strings.Count(spec[0:sep], refSpecWildcard)
 	wd := strings.Count(spec[sep+1:], refSpecWildcard)
-	return ws == wd && ws < 2 && wd < 2
+	if ws == wd && ws < 2 && wd < 2 {
+		return nil
+	}
+
+	return ErrRefSpecMalformedWildcard
 }
 
 // IsForceUpdate returns if update is allowed in non fast-forward merges