Prefer github remote over origin for coverage baseline

bake.rb

@@ -10,6 +10,7 @@ $LOAD_PATH.unshift(LIB_PATH) unless $LOAD_PATH.include?(LIB_PATH)
 require "pressa/drafts"
 require "pressa/coverage"
 require "pressa/publish"
+require "pressa/git"
 
 DRAFTS_DIR = "public/drafts".freeze
 PUBLISH_HOST = "mudge".freeze
@@ -272,12 +273,11 @@ end
 def preferred_remote
   upstream = capture_command_optional("git", "rev-parse", "--abbrev-ref", "--symbolic-full-name", "@{upstream}").strip
   upstream_remote = upstream.split("/").first unless upstream.empty?
-  return upstream_remote if upstream_remote && !upstream_remote.empty?
-
   remotes = capture_command("git", "remote").lines.map(&:strip).reject(&:empty?)
-  abort "Error: no git remotes configured; pass baseline=<ref>." if remotes.empty?
 
-  remotes.include?("origin") ? "origin" : remotes.first
+  Pressa::Git.choose_remote(remotes:, upstream_remote:)
+rescue Pressa::Git::Error => e
+  abort "Error: #{e.message}"
 end
 
 def remote_default_branch_ref(remote)

lib/pressa.rb

@@ -9,6 +9,7 @@ require "pressa/config/loader"
 require "pressa/drafts"
 require "pressa/coverage"
 require "pressa/publish"
+require "pressa/git"
 
 module Pressa
   def self.create_site(source_path: ".", url_override: nil, output_format: "html")

lib/pressa/git.rb

@@ -0,0 +1,23 @@
+module Pressa
+  # Pure git-related decisions for the coverage tasks. The actual git commands
+  # run in bake.rb; this just decides which remote to treat as canonical.
+  module Git
+    class Error < StandardError; end
+
+    # Remotes are preferred in this order when nothing else picks one.
+    DEFAULT_REMOTE_PREFERENCE = %w[github origin].freeze
+
+    module_function
+
+    # Pick the remote to resolve the coverage baseline against. An explicit
+    # upstream wins; otherwise fall back through the preference list, then to
+    # the first configured remote.
+    def choose_remote(remotes:, upstream_remote: nil, preference: DEFAULT_REMOTE_PREFERENCE)
+      return upstream_remote unless upstream_remote.to_s.empty?
+
+      raise Error, "no git remotes configured; pass baseline=<ref>." if remotes.empty?
+
+      preference.find { |name| remotes.include?(name) } || remotes.first
+    end
+  end
+end

test/git_test.rb

@@ -0,0 +1,32 @@
+require "test_helper"
+
+class Pressa::GitTest < Minitest::Test
+  def test_choose_remote_prefers_github_over_origin
+    assert_equal("github", Pressa::Git.choose_remote(remotes: ["origin", "github"]))
+  end
+
+  def test_choose_remote_falls_back_to_origin_when_no_github
+    assert_equal("origin", Pressa::Git.choose_remote(remotes: ["origin", "mirror"]))
+  end
+
+  def test_choose_remote_falls_back_to_first_remote_when_neither_preferred
+    assert_equal("mirror", Pressa::Git.choose_remote(remotes: ["mirror", "backup"]))
+  end
+
+  def test_choose_remote_honours_an_explicit_upstream_remote
+    assert_equal("fork", Pressa::Git.choose_remote(remotes: ["origin", "github"], upstream_remote: "fork"))
+  end
+
+  def test_choose_remote_returns_upstream_even_without_other_remotes
+    assert_equal("fork", Pressa::Git.choose_remote(remotes: [], upstream_remote: "fork"))
+  end
+
+  def test_choose_remote_raises_when_no_remotes_and_no_upstream
+    error = assert_raises(Pressa::Git::Error) { Pressa::Git.choose_remote(remotes: []) }
+    assert_match(/no git remotes/, error.message)
+  end
+
+  def test_choose_remote_accepts_a_custom_preference_order
+    assert_equal("upstream", Pressa::Git.choose_remote(remotes: ["origin", "upstream"], preference: ["upstream"]))
+  end
+end