Add max length option to BranchNamer

common/lib/dependabot/pull_request_creator.rb

@@ -48,7 +48,7 @@ def initialize(cause, pull_request)
                 :custom_labels, :author_details, :signature_key,
                 :commit_message_options, :vulnerabilities_fixed,
                 :reviewers, :assignees, :milestone, :branch_name_separator,
-                :branch_name_prefix, :github_redirection_service,
+                :branch_name_prefix, :branch_name_max_length, :github_redirection_service,
                 :custom_headers, :provider_metadata
 
     def initialize(source:, base_commit:, dependencies:, files:, credentials:,
@@ -57,7 +57,8 @@ def initialize(source:, base_commit:, dependencies:, files:, credentials:,
                    commit_message_options: {}, vulnerabilities_fixed: {},
                    reviewers: nil, assignees: nil, milestone: nil,
                    branch_name_separator: "/", branch_name_prefix: "dependabot",
-                   label_language: false, automerge_candidate: false,
+                   branch_name_max_length: nil, label_language: false,
+                   automerge_candidate: false,
                    github_redirection_service: DEFAULT_GITHUB_REDIRECTION_SERVICE,
                    custom_headers: nil, require_up_to_date_base: false,
                    provider_metadata: {}, message: nil)
@@ -78,6 +79,7 @@ def initialize(source:, base_commit:, dependencies:, files:, credentials:,
       @vulnerabilities_fixed      = vulnerabilities_fixed
       @branch_name_separator      = branch_name_separator
       @branch_name_prefix         = branch_name_prefix
+      @branch_name_max_length     = branch_name_max_length
       @label_language             = label_language
       @automerge_candidate        = automerge_candidate
       @github_redirection_service = github_redirection_service
@@ -232,7 +234,8 @@ def branch_namer
           files: files,
           target_branch: source.branch,
           separator: branch_name_separator,
-          prefix: branch_name_prefix
+          prefix: branch_name_prefix,
+          max_length: branch_name_max_length
         )
     end
 

common/lib/dependabot/pull_request_creator/branch_namer.rb

@@ -1,20 +1,23 @@
 # frozen_string_literal: true
 
+require "digest"
+
 require "dependabot/metadata_finders"
 require "dependabot/pull_request_creator"
 
 module Dependabot
   class PullRequestCreator
     class BranchNamer
-      attr_reader :dependencies, :files, :target_branch, :separator, :prefix
+      attr_reader :dependencies, :files, :target_branch, :separator, :prefix, :max_length
 
       def initialize(dependencies:, files:, target_branch:, separator: "/",
-                     prefix: "dependabot")
+                     prefix: "dependabot", max_length: nil)
         @dependencies  = dependencies
         @files         = files
         @target_branch = target_branch
         @separator     = separator
         @prefix        = prefix
+        @max_length    = max_length
       end
 
       def new_branch_name
@@ -37,7 +40,15 @@ def new_branch_name
           end
 
         # Some users need branch names without slashes
-        sanitize_ref(File.join(prefixes, @name).gsub("/", separator))
+        sanitized_name = sanitize_ref(File.join(prefixes, @name).gsub("/", separator))
+
+        # Shorten the ref in case users refs have length limits
+        if @max_length && (sanitized_name.length > @max_length)
+          sha = Digest::SHA1.hexdigest(sanitized_name)[0, @max_length]
+          sanitized_name[[@max_length - sha.size, 0].max..] = sha
+        end
+
+        sanitized_name
       end
 
       private
@@ -181,7 +192,7 @@ def requirements_changed?(dependency)
 
       def sanitize_ref(ref)
         # This isn't a complete implementation of git's ref validation, but it
-        # covers most cases that crop up. Its list of allowed charactersr is a
+        # covers most cases that crop up. Its list of allowed characters is a
         # bit stricter than git's, but that's for cosmetic reasons.
         ref.
           # Remove forbidden characters (those not already replaced elsewhere)

common/spec/dependabot/pull_request_creator/branch_namer_spec.rb

@@ -104,6 +104,49 @@
       it { is_expected.to eq("dependabot-dummy-business-1.5.0") }
     end
 
+    context "with a maximum length" do
+      let(:namer) do
+        described_class.new(
+          dependencies: dependencies,
+          files: files,
+          target_branch: target_branch,
+          max_length: max_length
+        )
+      end
+
+      context "with a maximum length longer than branch name" do
+        let(:max_length) { 35 }
+
+        it { is_expected.to eq("dependabot/dummy/business-1.5.0") }
+        its(:length) { is_expected.to eq(31) }
+      end
+
+      context "with a maximum length shorter than branch name" do
+        let(:dependency_name) { "business-and-work-and-desks-and-tables-and-chairs-and-lunch" }
+
+        context "with a maximum length longer than sha1 length" do
+          let(:max_length) { 50 }
+
+          it { is_expected.to eq("dependabot#{Digest::SHA1.hexdigest("dependabot/dummy/#{dependency_name}-1.5.0")}") }
+          its(:length) { is_expected.to eq(50) }
+        end
+
+        context "with a maximum length equal than sha1 length" do
+          let(:max_length) { 40 }
+
+          it { is_expected.to eq(Digest::SHA1.hexdigest("dependabot/dummy/#{dependency_name}-1.5.0")) }
+          its(:length) { is_expected.to eq(40) }
+        end
+
+        context "with a maximum length shorter than sha1 length" do
+          let(:max_length) { 20 }
+
+          it { is_expected.to eq(Digest::SHA1.hexdigest("dependabot/dummy/#{dependency_name}-1.5.0")[0...20]) }
+          its(:length) { is_expected.to eq(20) }
+        end
+      end
+    end
+
     context "with multiple dependencies" do
       let(:dependencies) { [dependency, dep2] }
       let(:dep2) do