more portable symlink awareness for START_CTX[:cwd]

`sh -c pwd` doesn't reliably read ENV["PWD"] on all platforms,
this means that directories that are symlinks may be ignored
and the real path is resolved.  This can be problematic when
doing upgrades for common deployment systems such as Capistrano
which rely on the working directory being a symlink.

1 files changed, 11 insertions, 3 deletions

diff --git a/lib/unicorn.rb b/lib/unicorn.rb
index ae1de59..de46c9e 100644
--- a/lib/unicorn.rb
+++ b/lib/unicorn.rb
@@ -92,9 +92,17 @@ module Unicorn
     #   Unicorn::HttpServer::START_CTX[0] = "/home/bofh/1.9.2/bin/unicorn"
     START_CTX = {
       :argv => ARGV.map { |arg| arg.dup },
-      # don't rely on Dir.pwd here since it's not symlink-aware, and
-      # symlink dirs are the default with Capistrano...
-      :cwd => `/bin/sh -c pwd`.chomp("\n"),
+      :cwd => lambda {
+          # favor ENV['PWD'] since it is (usually) symlink aware for
+          # Capistrano and like systems
+          begin
+            a = File.stat(pwd = ENV['PWD'])
+            b = File.stat(Dir.pwd)
+            a.ino == b.ino && a.dev == b.dev ? pwd : Dir.pwd
+          rescue
+            Dir.pwd
+          end
+        }.call,
       0 => $0.dup,
     }