Allow setting Gitaly's git.bin_path

Related to https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/11647

changelogs/unreleased/allow-setting-gitaly-git-bin-path.yml

+---
+title: Allow setting Gitaly's git.bin_path
+merge_request: 4668
+author:
+type: added

files/gitlab-config-template/gitlab.rb.template

@@ -1987,6 +1987,7 @@ external_url 'GENERATED_EXTERNAL_URL'
 # gitaly['auth_transitioning'] = false # When true, auth is logged to Prometheus but NOT enforced
 # gitaly['graceful_restart_timeout'] = '1m' # Grace time for a gitaly process to finish ongoing requests
 # gitaly['git_catfile_cache_size'] = 100 # Number of 'git cat-file' processes kept around for re-use
+# gitaly['git_bin_path'] = "/usr/bin/git" # A custom path for the 'git' executable
 # gitaly['open_files_ulimit'] = 15000 # Maximum number of open files allowed for the gitaly process
 # gitaly['ruby_max_rss'] = 300000000 # RSS threshold in bytes for triggering a gitaly-ruby restart
 # gitaly['ruby_graceful_restart_timeout'] = '10m' # Grace time for a gitaly-ruby process to finish ongoing requests

files/gitlab-cookbooks/gitaly/attributes/default.rb

@@ -23,6 +23,7 @@ default['gitaly']['storage'] = []
 default['gitaly']['auth_token'] = nil
 default['gitaly']['auth_transitioning'] = false
 default['gitaly']['git_catfile_cache_size'] = nil
+default['gitaly']['git_bin_path'] = nil
 default['gitaly']['open_files_ulimit'] = 15000
 default['gitaly']['ruby_max_rss'] = nil
 default['gitaly']['ruby_graceful_restart_timeout'] = nil

files/gitlab-cookbooks/gitaly/templates/default/gitaly-config.toml.erb

@@ -76,6 +76,9 @@ transitioning = <%= @auth_transitioning %>
 <% if @git_catfile_cache_size %>
 catfile_cache_size = <%= @git_catfile_cache_size %>
 <% end %>
+<% if @git_bin_path %>
+bin_path = <%= @git_bin_path %>
+<% end %>
 [gitaly-ruby]

spec/chef/recipes/gitaly_spec.rb

@@ -28,6 +28,7 @@ RSpec.describe 'gitaly' do
   let(:ruby_num_workers) { 5 }
   let(:ruby_rugged_git_config_search_path) { '/path/to/opt/gitlab/embedded/etc' }
   let(:git_catfile_cache_size) { 50 }
+  let(:git_bin_path) { '/path/to/usr/bin/git' }
   let(:open_files_ulimit) { 10000 }
   let(:default_vars) do
     {
@@ -173,6 +174,7 @@ RSpec.describe 'gitaly' do
           ruby_restart_delay: ruby_restart_delay,
           ruby_num_workers: ruby_num_workers,
           git_catfile_cache_size: git_catfile_cache_size,
+          git_bin_path: git_bin_path,
           open_files_ulimit: open_files_ulimit,
           ruby_rugged_git_config_search_path: ruby_rugged_git_config_search_path,
           daily_maintenance_start_hour: daily_maintenance_start_hour,