Default empty constraints to any, not the default branch

Author: carolynvs

internal/gps/source_manager.go

@@ -502,6 +502,10 @@ func (sm *SourceMgr) DeduceProjectRoot(ip string) (ProjectRoot, error) {
 // string. Preference is given first for revisions, then branches, then semver
 // constraints, and then plain tags.
 func (sm *SourceMgr) InferConstraint(s string, pi ProjectIdentifier) (Constraint, error) {
+	if s == "" {
+		return Any(), nil
+	}
+
 	slen := len(s)
 	if slen == 40 {
 		if _, err := hex.DecodeString(s); err == nil {
@@ -539,8 +543,7 @@ func (sm *SourceMgr) InferConstraint(s string, pi ProjectIdentifier) (Constraint
 	}
 	SortPairedForUpgrade(versions)
 	for _, v := range versions {
-		// Pick the default branch if no constraint is given
-		if s == "" || s == v.String() {
+		if s == v.String() {
 			version = v
 			break
 		}

internal/gps/source_manager_test.go

@@ -30,6 +30,7 @@ func TestSourceManager_InferConstraint(t *testing.T) {
 	}
 
 	constraints := map[string]Constraint{
+		"":       Any(),
 		"v0.8.1": sv,
 		"v2":     NewBranch("v2"),
 		"v0.12.0-12-de4dcafe0": svs,