Fix symlink issue. See https://drupal.org/node/1372442#comment-6099598
describing new "shallow-copy" option
implementing "shallow-copy" option for git downloads
shallow-clone and working-copy don''t making sense together
#924: Return an array from drush_invoke_process when executed in interactive mode.
Fix invalidation of update caches in Drupal 8.
Add --check-disabled option to pm-updatestatus.
#899: Improve escaping options for core-exec: allow --escape=0 to disable argument escaping. Suppress shell escaping for shell aliases in the usual case, when arguements are provided as a string.
Add tests for --check-disabled option pf pm-updatestatus.
Merge pull request #953 from jonhattan/update_status-check-disabled

Add --check-disabled option to pm-updatestatus.
Added path-aliases option %env-vars for adding environmental variables to generated Drush commands.
Moved %env-vars to the top-level of site record as #env-vars.
Set 'drush' as the default backend in update_status engine.
Parts of Drupal still require a global user object.

- Fixes issue #957.
- Increases bootstrap level of the `user-cancel` command
Adjust update_status drush backend to match output of update.module.
Adding links to core issue.
Fix #936. Global option for skipping cache-clear during updb
Merge pull request #958 from drush-ops/user-cancel

Parts of Drupal still require a global user object.
Merge pull request #955 from mortenson/master

Added %env-vars for adding environmental variables to Drush commands
Merge pull request #952 from greg-1-anderson/interactive-fix

#924: Return an array from drush_invoke_process