Testing: Allow newer components for local tests

Rebuilding Gitaly is done for a Gitaly version that mismatches the
GITALY_SERVER_VERSION. Due to a continuous deployment, these rebuilds
are quite frequent and thus triggered a lot.

This change allows a newer Gitaly to be used, locally, for these tests.
Which in practice will decrease the number of rebuilds.

This achieved by running `git merge-base --is-ancestor` in the tmp
component directory, and depends on the HEAD being the same as the built
assets.

The other option was to parse `gitaly -version`, but this wouldn't have
worked for `gitlab-shell` etc, and thus using HEAD as heuristic was
chosen.

spec/support/helpers/test_env.rb

@@ -517,6 +517,8 @@ module TestEnv
 
     return false if component_matches_git_sha?(component_folder, expected_version)
 
+    return false if component_ahead_of_target?(component_folder, expected_version)
+
     version = File.read(File.join(component_folder, 'VERSION')).strip
 
     # Notice that this will always yield true when using branch versions
@@ -527,6 +529,20 @@ module TestEnv
     true
   end
 
+  def component_ahead_of_target?(component_folder, expected_version)
+    # The HEAD of the component_folder will be used as heuristic for the version
+    # of the binaries, allowing to use Git to determine if HEAD is later than
+    # the expected version. Note: Git considers HEAD to be an anchestor of HEAD.
+    _out, exit_status = Gitlab::Popen.popen(%W[
+      #{Gitlab.config.git.bin_path}
+      -C #{component_folder}
+      merge-base --is-ancestor
+      #{expected_version} HEAD
+])
+
+    exit_status == 0
+  end
+
   def component_matches_git_sha?(component_folder, expected_version)
     # Not a git SHA, so return early
     return false unless expected_version =~ ::Gitlab::Git::COMMIT_ID