feat(helm): add support for repo alias

support repo alias in requirements.yaml
The syntax should be like: "alias:reponame" or "@reponame".

closes: #1985

docs/chart_best_practices/requirements.md

@@ -16,6 +16,8 @@ This will match version 1.2.0 and any patches to that release (1.2.1, 1.2.999, a
 
 Where possible, use `https://` repository URLs, followed by `http://` URLs.
 
+If the repository has been added to the repository index file, the repository name can be used as an alias of URL. Use `alias:` or `@` followed by repository names.
+
 File URLs (`file://...`) are considered a "special case" for charts that are assembled by a fixed deployment pipeline. Charts that use `file://` in a `requirements.yaml` file are not allowed in the official Helm repository.
 
 ## Conditions and Tags

docs/helm/helm_dependency.md

@@ -36,8 +36,20 @@ The 'version' field should contain a semantic version or version range.
 
 The 'repository' URL should point to a Chart Repository. Helm expects that by
 appending '/index.yaml' to the URL, it should be able to retrieve the chart
-repository's index. Note: 'repository' cannot be a repository alias. It must be
-a URL.
+repository's index.
+
+A repository can also be represented by a repository name defined in the index file
+in lieu of a repository URL. If a repository alias is used, it is expected to start with
+'alias:' or '@', followed by a repository name. For example,
+    # requirements.yaml
+    dependencies:
+    - name: nginx
+      version: "1.2.3"
+      repository: "alias:stable"
+
+Note: In the above example, if the '@' syntax is used, the repository alias '@stable'
+must be quoted, as YAML requires to use quotes if the value includes a special character
+like '@'.
 
 Starting from 2.2.0, repository can be defined as the path to the directory of
 the dependency charts stored locally. The path should start with a prefix of
@@ -53,7 +65,6 @@ If the dependency chart is retrieved locally, it is not required to have the
 repository added to helm by "helm add repo". Version matching is also supported
 for this case.
 
-
 ### Options inherited from parent commands
 
 ```

pkg/downloader/manager.go

@@ -124,6 +124,13 @@ func (m *Manager) Update() error {
 		}
 		return err
 	}
+
+	// Hash requirements.yaml
+	hash, err := resolver.HashReq(req)
+	if err != nil {
+		return err
+	}
+
 	// Check that all of the repos we're dependent on actually exist and
 	// the repo index names.
 	repoNames, err := m.getRepoNames(req.Dependencies)
@@ -140,7 +147,7 @@ func (m *Manager) Update() error {
 
 	// Now we need to find out which version of a chart best satisfies the
 	// requirements the requirements.yaml
-	lock, err := m.resolve(req, repoNames)
+	lock, err := m.resolve(req, repoNames, hash)
 	if err != nil {
 		return err
 	}
@@ -172,9 +179,9 @@ func (m *Manager) loadChartDir() (*chart.Chart, error) {
 // resolve takes a list of requirements and translates them into an exact version to download.
 //
 // This returns a lock file, which has all of the requirements normalized to a specific version.
-func (m *Manager) resolve(req *chartutil.Requirements, repoNames map[string]string) (*chartutil.RequirementsLock, error) {
+func (m *Manager) resolve(req *chartutil.Requirements, repoNames map[string]string, hash string) (*chartutil.RequirementsLock, error) {
 	res := resolver.New(m.ChartPath, m.HelmHome)
-	return res.Resolve(req, repoNames)
+	return res.Resolve(req, repoNames, hash)
 }
 
 // downloadAll takes a list of dependencies and downloads them into charts/
@@ -346,7 +353,13 @@ func (m *Manager) getRepoNames(deps []*chartutil.Dependency) (map[string]string,
 		found := false
 
 		for _, repo := range repos {
-			if urlutil.Equal(repo.URL, dd.Repository) {
+			if (strings.HasPrefix(dd.Repository, "@") && strings.TrimPrefix(dd.Repository, "@") == repo.Name) ||
+				(strings.HasPrefix(dd.Repository, "alias:") && strings.TrimPrefix(dd.Repository, "alias:") == repo.Name) {
+				found = true
+				dd.Repository = repo.URL
+				reposMap[dd.Name] = repo.Name
+				break
+			} else if urlutil.Equal(repo.URL, dd.Repository) {
 				found = true
 				reposMap[dd.Name] = repo.Name
 				break

pkg/downloader/manager_test.go

@@ -120,6 +120,20 @@ func TestGetRepoNames(t *testing.T) {
 			},
 			expect: map[string]string{"local-dep": "file://./testdata/signtest"},
 		},
+		{
+			name: "repo alias (alias:)",
+			req: []*chartutil.Dependency{
+				{Name: "oedipus-rex", Repository: "alias:testing"},
+			},
+			expect: map[string]string{"oedipus-rex": "testing"},
+		},
+		{
+			name: "repo alias (@)",
+			req: []*chartutil.Dependency{
+				{Name: "oedipus-rex", Repository: "@testing"},
+			},
+			expect: map[string]string{"oedipus-rex": "testing"},
+		},
 	}
 
 	for _, tt := range tests {

pkg/resolver/resolver.go

@@ -47,11 +47,7 @@ func New(chartpath string, helmhome helmpath.Home) *Resolver {
 }
 
 // Resolve resolves dependencies and returns a lock file with the resolution.
-func (r *Resolver) Resolve(reqs *chartutil.Requirements, repoNames map[string]string) (*chartutil.RequirementsLock, error) {
-	d, err := HashReq(reqs)
-	if err != nil {
-		return nil, err
-	}
+func (r *Resolver) Resolve(reqs *chartutil.Requirements, repoNames map[string]string, d string) (*chartutil.RequirementsLock, error) {
 
 	// Now we clone the dependencies, locking as we go.
 	locked := make([]*chartutil.Dependency, len(reqs.Dependencies))

pkg/resolver/resolver_test.go

@@ -104,7 +104,12 @@ func TestResolve(t *testing.T) {
 	repoNames := map[string]string{"alpine": "kubernetes-charts", "redis": "kubernetes-charts"}
 	r := New("testdata/chartpath", "testdata/helmhome")
 	for _, tt := range tests {
-		l, err := r.Resolve(tt.req, repoNames)
+		hash, err := HashReq(tt.req)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		l, err := r.Resolve(tt.req, repoNames, hash)
 		if err != nil {
 			if tt.err {
 				continue