Unity 2018.3.02f
upm-git-extension 0.9.1
git-dependency-resolver 1.1.0

GUID [06608ad179f2043e5a26ec668de262d6] for asset 'Packages/com.coffee.git-dependency-resolver/CHANGELOG.md' conflicts with:
'Packages/com.coffee.upm-git-extension/CHANGELOG.md'
We can't assign a new GUID because the asset is in an immutable folder. The asset will be ignored.

Examining CHANGELOG.md.meta (using the github interface) on both the git-depency-resolver and the upm-git-extension repositories shows that they have the same GUID:

guid: 06608ad179f2043e5a26ec668de262d6

Normally Unity would generate a new meta file but because the packages are in the PackageCache, they are immutable.

This error occurs for many files.