Support wildcard matches for protected branches at the model level.

1. The main implementation is in the `ProtectedBranch` model. The
   wildcard is converted to a Regex and compared. This has been tested
   thoroughly.

    - While `Project#protected_branch?` is the main entry point,
      `project#open_branches` and
      `project#developers_can_push_to_protected_branch?`
      have also been modified to work with wildcard protected branches.

    - The regex is memoized (within the `ProtectedBranch` instance)

2. Improve the performance of `Project#protected_branch?`

    -  This method is called from `Project#open_branches` once _per branch_
       in the project, to check if that branch is protected or not.

    -  Before, `#protected_branch?` was making a database call every
       time it was invoked (in the above case, that amounts to once
       per branch), which is expensive.

    -  This commit caches the list of protected branches in memory, which
       reduces the number of database calls down to 1.

    -  A downside to this approach is that `#protected_branch?` _could_
       return a stale value (due to the caching), but this is
       an acceptable tradeoff.

3. Remove the (now) unused `Project#protected_branch_names` method.

    - This was previously used to check for protected branch status.

1 files changed, 125 insertions, 0 deletions

diff --git a/spec/models/protected_branch_spec.rb b/spec/models/protected_branch_spec.rb
index b523834c6e9..8bf0d24a128 100644
--- a/spec/models/protected_branch_spec.rb
+++ b/spec/models/protected_branch_spec.rb
@@ -1,6 +1,8 @@
 require 'spec_helper'
 
 describe ProtectedBranch, models: true do
+  subject { build_stubbed(:protected_branch) }
+
   describe 'Associations' do
     it { is_expected.to belong_to(:project) }
   end
@@ -12,4 +14,127 @@ describe ProtectedBranch, models: true do
     it { is_expected.to validate_presence_of(:project) }
     it { is_expected.to validate_presence_of(:name) }
   end
+
+  describe "#matches?" do
+    context "when the protected branch setting is not a wildcard" do
+      let(:protected_branch) { build(:protected_branch, name: "production/some-branch") }
+
+      it "returns true for branch names that are an exact match" do
+        expect(protected_branch.matches?("production/some-branch")).to be true
+      end
+
+      it "returns false for branch names that are not an exact match" do
+        expect(protected_branch.matches?("staging/some-branch")).to be false
+      end
+    end
+
+    context "when the protected branch name contains wildcard(s)" do
+      context "when there is a single '*'" do
+        let(:protected_branch) { build(:protected_branch, name: "production/*") }
+
+        it "returns true for branch names matching the wildcard" do
+          expect(protected_branch.matches?("production/some-branch")).to be true
+          expect(protected_branch.matches?("production/")).to be true
+        end
+
+        it "returns false for branch names not matching the wildcard" do
+          expect(protected_branch.matches?("staging/some-branch")).to be false
+          expect(protected_branch.matches?("production")).to be false
+        end
+      end
+
+      context "when the wildcard contains regex symbols other than a '*'" do
+        let(:protected_branch) { build(:protected_branch, name: "pro.duc.tion/*") }
+
+        it "returns true for branch names matching the wildcard" do
+          expect(protected_branch.matches?("pro.duc.tion/some-branch")).to be true
+        end
+
+        it "returns false for branch names not matching the wildcard" do
+          expect(protected_branch.matches?("production/some-branch")).to be false
+          expect(protected_branch.matches?("proXducYtion/some-branch")).to be false
+        end
+      end
+
+      context "when there are '*'s at either end" do
+        let(:protected_branch) { build(:protected_branch, name: "*/production/*") }
+
+        it "returns true for branch names matching the wildcard" do
+          expect(protected_branch.matches?("gitlab/production/some-branch")).to be true
+          expect(protected_branch.matches?("/production/some-branch")).to be true
+          expect(protected_branch.matches?("gitlab/production/")).to be true
+          expect(protected_branch.matches?("/production/")).to be true
+        end
+
+        it "returns false for branch names not matching the wildcard" do
+          expect(protected_branch.matches?("gitlabproductionsome-branch")).to be false
+          expect(protected_branch.matches?("production/some-branch")).to be false
+          expect(protected_branch.matches?("gitlab/production")).to be false
+          expect(protected_branch.matches?("production")).to be false
+        end
+      end
+
+      context "when there are arbitrarily placed '*'s" do
+        let(:protected_branch) { build(:protected_branch, name: "pro*duction/*/gitlab/*") }
+
+        it "returns true for branch names matching the wildcard" do
+          expect(protected_branch.matches?("production/some-branch/gitlab/second-branch")).to be true
+          expect(protected_branch.matches?("proXYZduction/some-branch/gitlab/second-branch")).to be true
+          expect(protected_branch.matches?("proXYZduction/gitlab/gitlab/gitlab")).to be true
+          expect(protected_branch.matches?("proXYZduction//gitlab/")).to be true
+          expect(protected_branch.matches?("proXYZduction/some-branch/gitlab/")).to be true
+          expect(protected_branch.matches?("proXYZduction//gitlab/some-branch")).to be true
+        end
+
+        it "returns false for branch names not matching the wildcard" do
+          expect(protected_branch.matches?("production/some-branch/not-gitlab/second-branch")).to be false
+          expect(protected_branch.matches?("prodXYZuction/some-branch/gitlab/second-branch")).to be false
+          expect(protected_branch.matches?("proXYZduction/gitlab/some-branch/gitlab")).to be false
+          expect(protected_branch.matches?("proXYZduction/gitlab//")).to be false
+          expect(protected_branch.matches?("proXYZduction/gitlab/")).to be false
+          expect(protected_branch.matches?("proXYZduction//some-branch/gitlab")).to be false
+        end
+      end
+    end
+  end
+
+  describe "#matching" do
+    context "for direct matches" do
+      it "returns a list of protected branches matching the given branch name" do
+        production = create(:protected_branch, name: "production")
+        staging = create(:protected_branch, name: "staging")
+
+        expect(ProtectedBranch.matching("production")).to include(production)
+        expect(ProtectedBranch.matching("production")).not_to include(staging)
+      end
+
+      it "accepts a list of protected branches to search from, so as to avoid a DB call" do
+        production = build(:protected_branch, name: "production")
+        staging = build(:protected_branch, name: "staging")
+
+        expect(ProtectedBranch.matching("production")).to be_empty
+        expect(ProtectedBranch.matching("production", protected_branches: [production, staging])).to include(production)
+        expect(ProtectedBranch.matching("production", protected_branches: [production, staging])).not_to include(staging)
+      end
+    end
+
+    context "for wildcard matches" do
+      it "returns a list of protected branches matching the given branch name" do
+        production = create(:protected_branch, name: "production/*")
+        staging = create(:protected_branch, name: "staging/*")
+
+        expect(ProtectedBranch.matching("production/some-branch")).to include(production)
+        expect(ProtectedBranch.matching("production/some-branch")).not_to include(staging)
+      end
+
+      it "accepts a list of protected branches to search from, so as to avoid a DB call" do
+        production = build(:protected_branch, name: "production/*")
+        staging = build(:protected_branch, name: "staging/*")
+
+        expect(ProtectedBranch.matching("production/some-branch")).to be_empty
+        expect(ProtectedBranch.matching("production/some-branch", protected_branches: [production, staging])).to include(production)
+        expect(ProtectedBranch.matching("production/some-branch", protected_branches: [production, staging])).not_to include(staging)
+      end
+    end
+  end
 end