Only change file permission to default if no permission is configured

[jjohannes]

Working theory:
The documentation of FilePermissions states:

The default permissions used differ between files and directories and are as follows:
[...] FILE: [...] (0644, rw-r--r--)

It's not very clear what that means, but it may mean that if you query for the permissions of a file, but no permission was configured, you get this default.

We could use that to check if a permission was potentially not set and only set it then. This will either:

• Override an permission explicitly set to 644 with the same value (no-op)
• Set the 644 for a undefined permission (this is what we want for reproducibility)

if (file.getPermissions().toString().equals("644")) {
  file.permissions(p -> p.unix("644"));
}

For files that were alreay configured explicitly, for example by the application plugin, we will do nothing.
This would fix #7.

[britter]

Okay so your theory is:

• If the OS or file system created a file with permissions different from 644, Gradle would still report 644 if nobody else configured it.
• In this case we explicitly configure 644 to make sure the file gets this permissions.
• If getFilePermissions() returns something else, then somebody must have explicitly configured it in Gradle. In this case we don't touch it.

This would work if it's really the behavior of the file permissions API. I think we need to read the code to understand what's going on there. Also it looks like it will result in an ordering problem, because the application plugin could be applied after the reproducible builds plugin and the callback to set file permissions would be executed after the one registered by this plugin.

[jjohannes]

This would work if it's really the behavior of the file permissions API. I think we need to read the code to understand what's going on there.

Yes. We have to do that and/or run some tests.

Also it looks like it will result in an ordering problem, because the application plugin could be applied after the reproducible builds plugin and the callback to set file permissions would be executed after the one registered by this plugin.

That should not be a problem, because then the application plugin will overwrite what reproducible-builds configured. If you apply application after reproducible-builds, it should work with the current release already.

[britter]

That should not be a problem, because then the application plugin will overwrite what reproducible-builds configured. If you apply application after reproducible-builds, it should work with the current release already.

Oh yeah, that makes sense!