ruby: Read `HEAD` via Ruggedpks-ruby-reduce-usage-of-git

The `#head_symbolic_ref` function is using git-symbolic-ref(1) to read
the repo's `HEAD` symbolic reference. We're slowly phasing out all
executions of the Git command line though, and we can easily implement
it via Rugged.

Convert the function to use Rugged to read the reference. This allows us
to get rid of the now-unused `#run_git` function, and furthermore we
don't have to inject configuration for git-symbolic-ref(1) into the
sidecar anymore.

2 files changed, 6 insertions, 17 deletions

diff --git a/internal/git/command_factory.go b/internal/git/command_factory.go
index 653bde385..9f9cb5c81 100644
--- a/internal/git/command_factory.go
+++ b/internal/git/command_factory.go
@@ -533,10 +533,9 @@ func (cf *ExecCommandFactory) SidecarGitConfiguration(ctx context.Context) ([]Co
 	}
 
 	// ... as well as all configuration that exists for specific Git subcommands. The sidecar
-	// only executes git-symbolic-ref(1) and git-update-ref(1) nowadays, and this set of
-	// commands is not expected to grow anymore. So while really intimate with how the sidecar
-	// does this, it is good enough until we finally remove it.
-	options = append(options, commandDescriptions["symbolic-ref"].opts...)
+	// only executes git-update-ref(1) nowadays, and this set of commands is not expected to
+	// grow anymore. So while really intimate with how the sidecar does this, it is good enough
+	// until we finally remove it.
 	options = append(options, commandDescriptions["update-ref"].opts...)
 
 	// Convert the `GlobalOption`s into `ConfigPair`s.
diff --git a/ruby/lib/gitlab/git/repository.rb b/ruby/lib/gitlab/git/repository.rb
index b2b0c1fb9..cbe5bde19 100644
--- a/ruby/lib/gitlab/git/repository.rb
+++ b/ruby/lib/gitlab/git/repository.rb
@@ -250,25 +250,15 @@ module Gitlab
       end
 
       def head_symbolic_ref
-        message, status = run_git(%w[symbolic-ref HEAD])
+        head = rugged.ref('HEAD')
 
-        return 'main' if status.nonzero?
+        return 'main' if head.type != :symbolic
 
-        Ref.extract_branch_name(message.squish)
+        Ref.extract_branch_name(head.target_id)
       end
 
       private
 
-      def run_git(args, chdir: path, env: {}, nice: false, include_stderr: false, lazy_block: nil, &block)
-        cmd = [Gitlab.config.git.bin_path, *args]
-        cmd.unshift("nice") if nice
-
-        object_directories = alternate_object_directories
-        env['GIT_ALTERNATE_OBJECT_DIRECTORIES'] = object_directories.join(File::PATH_SEPARATOR) if object_directories.any?
-
-        popen(cmd, chdir, env, include_stderr: include_stderr, lazy_block: lazy_block, &block)
-      end
-
       def branches_filter(filter: nil, sort_by: nil)
         branches = rugged.branches.each(filter).map do |rugged_ref|
           begin