fix: major version revving in go modules

`gotagger` was filtering out all tags that didn't match the major
ersion of the module. This changes the logic to only filter out tags
whose major version is greater than the module version.

Fixes #17

Author: wfscheper

.stentor.d/17-fix-major-versioning.md

@@ -0,0 +1,6 @@
+Fixed a bug where `gotagger` calculated the wrong major version for go modules.
+
+When finding the latest tag for a go module,
+`gotagger` was only considering tags that matched the major version of the module.
+This caused `gotagger` to essentially always calculate the version as `v1.0.0`.
+The filtering was changed to only filter out tags whose major version are greater than the module version.

gotagger.go

@@ -45,7 +45,7 @@ type Config struct {
 	ExcludeModules []string
 
 	// IgnoreModules controls whether gotagger will ignore the existence of
-	// go.mod files when determinging how to version a project.
+	// go.mod files when determining how to version a project.
 	IgnoreModules bool
 
 	// RemoteName represents the name of the remote repository. Defaults to origin.
@@ -118,7 +118,7 @@ func (g *Gotagger) ModuleVersions(names ...string) ([]string, error) {
 	return g.versions(modules, nil)
 }
 
-// TagRepo determines the curent version of the repository by parsing the commit
+// TagRepo determines the current version of the repository by parsing the commit
 // history since the previous release and returns that version. Depending
 // on the CreateTag and PushTag configuration options tags may be created and
 // pushed.
@@ -351,12 +351,25 @@ func (g *Gotagger) latest(tags []string) (latest *semver.Version, hash string, e
 	return
 }
 
-func (g *Gotagger) latestModule(m module, tags []string) (*semver.Version, string, error) {
-	var hash string
-	latest := &semver.Version{}
+// latestModule returns the latest version of m and the hash of the commit
+// tagged with that version.
+func (g *Gotagger) latestModule(m module, tags []string) (latest *semver.Version, hash string, err error) {
+	majorVersion := strings.TrimPrefix(versionRegex.FindString(m.name), goModSep)
+	if majorVersion == "" {
+		majorVersion = "v1"
+	}
+	moduleVersion, err := semver.NewVersion(majorVersion + ".0.0")
+	if err != nil {
+		return nil, "", err
+	}
+
+	maximumVersion := moduleVersion.IncMajor()
+	latest = new(semver.Version)
 	for _, tag := range tags {
+		// strip the module prefix from the tag so we can parse it as a semver
 		tagName := strings.TrimPrefix(tag, m.prefix)
-		if tver, err := semver.NewVersion(tagName); err == nil && latest.LessThan(tver) {
+		// we want the highest version that is less than the next major version
+		if tver, err := semver.NewVersion(tagName); err == nil && tver.LessThan(&maximumVersion) && tver.GreaterThan(latest) {
 			hash, err = g.repo.RevParse(tag + "^{commit}")
 			if err != nil {
 				return nil, "", err
@@ -435,16 +448,13 @@ func (g *Gotagger) versionsModules(modules []module, commitModules []module) ([]
 		// version prefix, and the major version of this module.
 		// the major version is the version part of the module name
 		// (foo/v2, foo/v3) normalized to 'X.'
-		var prefixes []string
-		if major := strings.TrimPrefix(versionRegex.FindString(mod.name), goModSep); major == "" {
-			// no major version in module name, so v0.x and v1.x are allowed
-			prefixes = []string{mod.prefix + "v0.*", mod.prefix + "v1.*"}
-		} else {
-			prefixes = []string{mod.prefix + major + ".*"}
+		prefix := g.Config.VersionPrefix
+		if mod.prefix != "" {
+			prefix = mod.prefix + prefix
 		}
 
 		// get tags that match the prefixes
-		tags, err := g.repo.Tags(head, prefixes...)
+		tags, err := g.repo.Tags(head, prefix)
 		if err != nil {
 			return nil, err
 		}
@@ -669,7 +679,7 @@ func validateCommitModules(commitModules, changedModules []module) (err error) {
 	return
 }
 
-// TagRepo determines what the curent version of the repository is by parsing the commit
+// TagRepo determines what the current version of the repository is by parsing the commit
 // history since previous release and returns that version. Depending on the state of
 // the Config passed it, it may also create the tag and push it.
 //