Add options for specifying specific package versions

Here is the patch.

The updated help explains basic usage.

I try not to get too clever with parsing major/minor version numbers etc - the update service provides an exhaustive list of possibilities, so we let that do the work. Basically we detect the version number as either -HEAD, or -[number].[number or x]*. Then we try and match this exactly with the options provided by the service. If that doesn't match we also test matching with the Drupal version branch prepended, so that you can actually leave this out if you like, as a shortcut.

If you specify the major Drupal version different from the one you are running, it will actually install that version - however I think this functionality is for advanced users, so it is easier to give them that power (sometimes you do actually want to do that - e.g. with Drupal-HEAD right now). Drupal 6 prevents you activating a module with the wrong Drupal major version (without hacking the .info first), which is a safeguard too.

Project name/version strings that should be accepted:
project
project-5.x-1.0
project-5.x-1.x-dev
project-1.0
project-1.x-dev
project-1.1-rc1

I took another look at the update issue, and as far as I can tell this is really a cvs_deploy issue, rather than a drush_pm issue. Specifically I get this problem with modules marked with "Invalid info" on the update status page - if cvs_deploy is not inserting a (correct) module version to the info array then drush ignores any potential upgrades (and returns "ignored: Invalid info"), which is the existing and I think probably the safest drush behavior in this case.

If I fetch a module with wget, then the version info is returned correctly, and I have tested that I can upgrade the module with either drush_pm_cvs or drush_pm_wget.

Here is a patch that fixes the existing module check regression that we identified on IRC.

I figured out the update problem by the way - you need the latest update_status 2.2 to work with cvs_deploy - once I had corrected that versions were correctly detected and updates installed.

It should be noted that this patch currently only allows you to install specific versions, and not update to specific versions (i.e. it will only update to the latest stable version). If we want to be able to drush pm update to an arbitrary version then this will take some work refactoring drush_pm_update().

Fixes bug with reporting project name in error/success messages

Here ya go - this also removes a print_r() I found in update (from another patch, I guess)

Thanks Moshe :)