[GEOS-11332] Renaming style with uppercase/downcase empty the sld file

[aaime]

Nasty little bug that causes "data loss" (as in, stylesheet loss)

Checklist

• I have read the contribution guidelines.
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For core and extension modules:

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[aaime]

@jodygarnett do you have 5 minutes for a review? It's loosely in Resource area, while it does not change it directly, the method is being used by it to handle renames. The original code was written with case-insensitive file systems in mind, and causes data loss on Linux (style body is lost, at least from the UI, takes a little digging into the data dir to recover it).

[jodygarnett]

Wow the is a challenge, there is no way I know in java to detect if a file system is case sensitive.

[aaime]

Yes, neither do I. But Files.move should figure it out by itself