Run exec() checking when module is installed as it would not work at all without it

At least for the purposes of Upgrade Status, we can disable the version checking feature if you don't allow exec or return an unknown version number. Git deploy could resolve that by itself anyway, as it needs some fallback for when it cannot work. So moving to that queue.

Well, git deploy attempts to augment the project info from packages. If it cannot exec() it should "fail silently" at least when it works. I can produce a status report warning that it is uselessly installed, but it would need to deal with this itself IMHO. Modules depending it cannot really tell what is the internal architecture of the module.

Git Deploy displays an error on the Drupal status page if it is installed on a site with exec disabled.

Git Deploy should be uninstalled if exec is disabled.

Displaying an error on the status report page is not really helpful especially when using other projects that depend on git_deploy. Also uninstalling git_deploy in this case would not be useful for eg. upgrade_status which would also need to be uninstalled, even though it could do useful things without git_deploy, just not that useful. Git_deploy should by itself have a fail condition for when exec() is not enabled.

Git Deploy should not be installed at all if git is not executable, because it cannot do anything. Projects that don’t require Git Deploy to work should not depend on it. Upgrade Status should implement its own message for the status page to notify admins of reduced functionality without Git Deploy.

I have provided a patch that clarifies the error message and prevents Git Deploy from being installed when the git binary is missing or not executable.

Thanks @Darren Oh! Worked further from your patch to include specific messaging as to what the problem is so people have an easier time to debug / fix.