Introduce version package

version/go.mod

@@ -0,0 +1,5 @@
+module github.com/fluxcd/pkg/version
+
+go 1.15
+
+require github.com/Masterminds/semver/v3 v3.1.0

version/go.sum

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+github.com/Masterminds/semver/v3 v3.1.0 h1:Y2lUDsFKVRSYGojLJ1yLxSXdMmMYTYls0rCvoqmMUQk=
+github.com/Masterminds/semver/v3 v3.1.0/go.mod h1:VPu/7SZ7ePZ3QOrcuXROw5FAcLl4a0cBrbBpGY/8hQs=

version/version.go

@@ -0,0 +1,33 @@
+/*
+Copyright 2020 The Flux CD contributors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package version
+
+import (
+	"strings"
+
+	"github.com/Masterminds/semver/v3"
+)
+
+// ParseVersion behaves as semver.StrictNewVersion, with as sole exception
+// that it allows versions with a preceding "v" (i.e. v1.2.3).
+func ParseVersion(v string) (*semver.Version, error) {
+	vLessV := strings.TrimPrefix(v, "v")
+	if _, err := semver.StrictNewVersion(vLessV); err != nil {
+		return nil, err
+	}
+	return semver.NewVersion(v)
+}

version/version_test.go

@@ -0,0 +1,49 @@
+/*
+Copyright 2020 The Flux CD contributors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package version
+
+import (
+	"testing"
+)
+
+func TestParseVersion(t *testing.T) {
+	tests := []struct {
+		version string
+		err     bool
+	}{
+		{"v1.2.3", false},
+		{"v1.0", true},
+		{"v1", true},
+		{"v1.2.beta", true},
+		{"v1.2-5", true},
+		{"v1.2-beta.5", true},
+		{"\nv1.2", true},
+		{"v1.2.0-x.Y.0+metadata", false},
+		{"v1.2.0-x.Y.0+metadata-width-hypen", false},
+		{"v1.2.3-rc1-with-hypen", false},
+		{"v1.2.3.4", true},
+	}
+
+	for _, tc := range tests {
+		_, err := ParseVersion(tc.version)
+		if tc.err && err == nil {
+			t.Fatalf("expected error for version: %s", tc.version)
+		} else if !tc.err && err != nil {
+			t.Fatalf("error for version %s: %s", tc.version, err)
+		}
+	}
+}