Update manifest.Fetch to also parse "tag" from repo strings

manifest/fetch.go

@@ -2,11 +2,12 @@ package manifest
 
 import (
 	"fmt"
-	"os"
 	"net/http"
 	"net/url"
+	"os"
 	"path"
 	"path/filepath"
+	"strings"
 )
 
 // "dir" is the default "library directory"
@@ -14,19 +15,26 @@ import (
 //   if "repo" is a URL, the remote contents of that URL
 //   the file "repo"
 //   the file "dir/repo"
-func Fetch(dir, repo string) (string, *Manifest2822, error) {
+// (repoName, tagName, man, err)
+func Fetch(dir, repo string) (string, string, *Manifest2822, error) {
 	repoName := path.Base(repo)
+	tagName := ""
+	if tagIndex := strings.IndexRune(repoName, ':'); tagIndex > 0 {
+		tagName = repoName[tagIndex+1:]
+		repoName = repoName[:tagIndex]
+		repo = strings.TrimSuffix(repo, ":"+tagName)
+	}
 
 	u, err := url.Parse(repo)
 	if err == nil && u.IsAbs() {
 		// must be remote URL!
 		resp, err := http.Get(repo)
 		if err != nil {
-			return repoName, nil, err
+			return repoName, tagName, nil, err
 		}
 		defer resp.Body.Close()
 		man, err := Parse(resp.Body)
-		return repoName, man, err
+		return repoName, tagName, man, err
 	}
 
 	// try file paths
@@ -36,14 +44,14 @@ func Fetch(dir, repo string) (string, *Manifest2822, error) {
 	} {
 		f, err := os.Open(fileName)
 		if err != nil && !os.IsNotExist(err) {
-			return repoName, nil, err
+			return repoName, tagName, nil, err
 		}
 		if err == nil {
 			defer f.Close()
 			man, err := Parse(f)
-			return repoName, man, err
+			return repoName, tagName, man, err
 		}
 	}
 
-	return repoName, nil, fmt.Errorf("unable to find a manifest named %q (in %q or as a remote URL)", repo, dir)
+	return repoName, tagName, nil, fmt.Errorf("unable to find a manifest named %q (in %q or as a remote URL)", repo, dir)
 }