When Drush Make fails to apply patches...
These last few days, I had noticed a problem with Drush Make and patches: some patches, be they rolled by our team or from elsewhere, would apply without a glitch, but some others, which worked normally according to the test bot on Drupal.org, would fail to apply without any obvious reason.
I had mostly put it out of my list of pressing issues when I really had to use an old version of OpenLayers, 7.x-2.0-alpha2 to be specific, AND apply a patch fixing one of the bugs in that module: behaviors plugin not being located correctly (http://drupal.org/node/1898662 if you want details). So I rolled the patch, tested it locally, the qa.d.o bot applied it and did not report more errors than expected for that old version.... and my Drush Make install refused to apply it.
Here was the relevant excerpt:
projects[domain] = 3.7
projects[domain][patch] = "http://drupal.org/files/domain-foreach_argument-1879502-1.patch"
projects[openlayers] = 2.0-alpha2
projects[openlayers][patch] = "http://drupal.org/files/0001-Fix-the-path-file-declaration-for-behaviors.patch"
The Domain patch applied normally, but the OpenLayers patch would't apply. What could be wrong ?