Changes since 6.0.0, in reverse chrono order:
6ce93a6 #132: Avoid calling pm-updatecode-postupdate in pm-update.
7e28c04 Support 0 in addition to 'no' as value of --sanitize-password|email options.
538b615 Fix #109. drush status's 'PHP configuration' should reflect the setting of the DRUSH_INI environment variable.
67372ba Add --field-labels option, so that users may omit field labels from command output if they do not want them.
17bc29b Add CONTRIBUTING.md from the master branch.
3a1620b README.md changes from the master branch: support section, notes on assigning issues, moving usage up, add links to old drupal.org issues.
91bc8e4 Split table list returned by _drush_sql_get_db_table_list() correctly when on windows. Exploding the newline-seperated string of table names only on newline characters (\n) leaves all corresponding carriage return (\r) chars behind. confusing all checks performed directly on the array, such as in_array. As e.g "sessions" != "sessions\r", $skip_tables oder $structure_tables will only contain the respective setting's last element.
aed5d04 Fixing cygwin path conversion (See https://drupal.org/node/2036001)
e8951d7 #86: Include database name in confirmation message for sql-drop.
7c46e66 #48: Fix broken --exclude-other-sites option.
2c08439 Affiliate cron help topic to core-cron command.
4ba6ffe use drush_op() instead of call_user_func()
20ba347 Fix bug in drush_tarball_extract that caused the wrong thing to be returned in the file list if $destination was specified when a zip file was extracted.
5309a69 Make _drush_add_commandfiles() more robust at detecting and avoiding double-loading Drush commandfiles.
6c4beb1 Refactor drush_valid_drupal_root() to avoid a second function with checks.
6c1b2f2 drush_valid_drupal_root() requires only a file called includes/common.inc to match a Drupal directory, which causes problems when this file pattern appears elsewhere, in non-Drupal root contexts (e.g. in module_builder module).
bff8961 #52: Simplify code to automatically set the label separator.
f94f3c3 #52: Automatically set the label separator to the list separator when csv, etc. is selected with @sites (or other multi-site commands)
86259c5 Call drush_set_error so that an error status result code will be set when attempting to download a project that does not exist.
1d0107a Fix a couple of undefined offset warnings when running --version with a remote site alias.
e81b76c Remove Drupal 8 specific files from 6.x branch as they can't be run.
5f94226 Update docs to reflect var_export outputformat name.
3d3d428 Avoid bootstrap when --db-spec is sent.
327a8d3 Don't call drush_set_error in API function _drush_sql_query(); call it in command callback, drush_sql_query().
252771a Change travis to test 6.x and 5.x branches.
633eac4 backport docs enhancements to site-set.
31a28ed Hide site-reset command as it is removed in Drush 7 and now deprecated in Drush6. Use site-set without an argument.
9bc7b65 Fix #40. Added commented out shell alias as discussed. I also fixed a nasty shell alias bug which this revealed. It had been previously reported at https://drupal.org/node/1967346. I used str_getcsv() to fix it and that function is not available in php 5.2 so backport to 5.x needs work.
c85ec9f Add config link for modules in output of pm-info command
b18d46f Fix command name typo - usage-view should be usage-show
a9cf2ae Insure that Drush will set an error status code from sql-query if the query fails for any reason. Fixes #34.
9e4c033 #8: Insure that cache-get and config-get help only shows output formats that are usable by these commands.
9f93502 #8: If a field's human-readable name differs from its machine name, then show both in the help text output
6450b61 If a Drush command returns a string value, then print it, even if the command does not define an outputformat record in its command definition.
a65f369 This fixes #7. Use array_merge_recursive to combine metadata in outputformat process() function instead of array += operator, which can cause sections of the metadata to be lost. This was breaking drush_format in some instances, which broke the outputformat topic (e.g. for csv)
451ab38 Avoid '--invoke is an unrecognized option' error when Drush6 receives a backend request from a prior version of Drush.
d9e8ebc Merge pull request #13 from cyberwolf/test-result-xml-escaping
38d04ef Ensure system-err and system-out contents are properly escaped.
3fcef17 Stop spewing status info during archive-dump.