Previously, any comments inside the required provider configuration for
a given provider would be wiped out upon rerunning the 0.13upgrade
command. This commit attempts to preserve those comments if the existing
entry is semantically equivalent to the entry we are about to write.
This commit implements most of the intended functionality of the upgrade
command for rewriting configurations.
For a given module, it makes a list of all providers in use. Then it
attempts to detect the source address for providers without an explicit
source.
Once this step is complete, the tool rewrites the relevant configuration
files. This results in a single "required_providers" block for the
module, with a source for each provider.
Any providers for which the source cannot be detected (for example,
unofficial providers) will need a source to be defined by the user. The
tool writes an explanatory comment to the configuration to help with
this.
Alisdair McDiarmid