Allow for alterations of URLs being purged

Could you handle this by the domain override $conf var in your settings.php file?

Chris actually has a point here, his use case won't be supported with the current code as Acquia Purge will always use and respect base_path() when purging things. Setting different domains won't make this any different as it will then be a different domain in the URL, with still the wrong base path appended to it (and prefixed to the path).

So I thought about this and decided that altering $request is too much power to be given away but that a setting could fix this easily:

[7.x-1.x 515c705] 2312117: allow site administrator to differentiate the base_path being purged.
 3 files changed, 13 insertions(+), 2 deletions(-)

This is added to README.txt as of version 7.x-1.0:

setting: acquia_purge_base_path
default: (automatic)

In some cases Drupal isn't served on the same URL as where its edited, which will cause different paths to be purged than necessary. By overriding this setting, Drupal's base_path() will no longer be used to construct purges. Use only when you know what you are doing.
$conf['acquia_purge_base_path'] = '/sub/';

So now you could do in settings.php:

$conf['acquia_purge_base_path'] = '/foo/';

$ drush --uri=http://mysite.com/ ap-purge '/ bar'

# 6 items left...
Purged: http://mysite.com/foo/
Purged: http://mysite.com/foo/index.php
Purged: http://mysite.com/foo/index.php/
Purged: http://mysite.com/foo/bar
Purged: http://mysite.com/foo/bar/
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