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, 36 insertions, 0 deletions

diff --git a/app/models/protected_branch.rb b/app/models/protected_branch.rb
index 33cf046fa75..3db1ab0e5f9 100644
--- a/app/models/protected_branch.rb
+++ b/app/models/protected_branch.rb
@@ -8,4 +8,40 @@ class ProtectedBranch < ActiveRecord::Base
   def commit
     project.commit(self.name)
   end
+
+  # Returns all protected branches that match the given branch name.
+  # This realizes all records from the scope built up so far, and does
+  # _not_ return a relation.
+  #
+  # This method optionally takes in a list of `protected_branches` to search
+  # through, to avoid calling out to the database.
+  def self.matching(branch_name, protected_branches: nil)
+    (protected_branches || all).select { |protected_branch| protected_branch.matches?(branch_name) }
+  end
+
+  # Checks if the protected branch matches the given branch name.
+  def matches?(branch_name)
+    return false if self.name.blank?
+
+    exact_match?(branch_name) || wildcard_match?(branch_name)
+  end
+
+  protected
+
+  def exact_match?(branch_name)
+    self.name == branch_name
+  end
+
+  def wildcard_match?(branch_name)
+    wildcard_regex === branch_name
+  end
+
+  def wildcard_regex
+    @wildcard_regex ||= begin
+      name = self.name.gsub('*', 'STAR_DONT_ESCAPE')
+      quoted_name = Regexp.quote(name)
+      regex_string = quoted_name.gsub('STAR_DONT_ESCAPE', '.*?')
+      /\A#{regex_string}\z/
+    end
+  end
 end