Problem: omnigres packages occassionally conflicting

This happens because `pgpm` calls them in parallel threads and they
attempt to clone the same Omnigres revision into the same directory at
the same time.

Solution: punt it with a mutex
(and make sure `pgpm` uses threads)

Author: yrashk

exe/pgpm

@@ -5,6 +5,7 @@ require "bundler/setup"
 require "pgpm"
 require "dry/cli"
 require "parallel"
+require "etc"
 
 module Pgpm
   module CLI
@@ -48,7 +49,7 @@ module Pgpm
 
           # puts "There is no build support for OS distribution `#{os}`"
           # exit(1)
-          pkgs = Parallel.flat_map(packages) do |package|
+          pkgs = Parallel.flat_map(packages, in_threads: Etc.nprocessors) do |package|
             name, version = package.split("@")
             version ||= :latest
             p = Pgpm::Package[name]
@@ -122,7 +123,7 @@ module Pgpm
           Pgpm.load_packages(pkgdir)
 
           query_regexp = Regexp.new(query, "i")
-          Parallel.filter_map(Pgpm::Package) do |p|
+          Parallel.filter_map(Pgpm::Package, in_threads: Etc.nprocessors) do |p|
             next if p.contrib?
 
             matches = p.all_searchable_texts.any? do |t|

packages/omnigres/extension_discovery.rb

@@ -7,20 +7,27 @@ module Omnigres
   class ExtensionDiscovery
     @@extensions = {}
     @@git_revisions = {}
+    @mutex = Mutex.new
+
+    class << self
+      attr_reader :mutex # Expose a class-level reader for the mutex
+    end
 
     def initialize(revision: nil, path: nil)
       return if @@extensions[revision]
 
       suffix = revision ? "-#{revision}" : nil
       path ||= Pgpm::Cache.directory.join("omnigres#{suffix}")
-      git =
-        if File.directory?(path)
-          ::Git.open(path)
-        else
-          ::Git.clone("https://github.com/omnigres/omnigres", path)
-        end
-      git.checkout(revision) if revision
-      @git = git
+      self.class.mutex.synchronize do
+        git =
+          if File.directory?(path)
+            ::Git.open(path)
+          else
+            ::Git.clone("https://github.com/omnigres/omnigres", path)
+          end
+        git.checkout(revision) if revision
+        @git = git
+      end
     end
 
     attr_reader :git