Summary

Currently CopyToOutputDirectory can only be Never, Always and PreserveNewest. (https://learn.microsoft.com/en-us/visualstudio/msbuild/common-msbuild-project-items)
This can cause problems when the content file is for some reason changed to the older copy, but still expected to be copied.

Sample scenarios when this might be needed:

• Nuget content files copy on downgrading package (NuGet package contentFiles don't get copied when downgrading package on incremental build NuGet/Home#12578)
• Decreasing the motivation to use Allways (New diagnostic proposal: erroring on CopyToOutputDirectory="Always" #7654)
• Reverting/Undeleting files via OS or 3rd pty functionality (not git - as it always updates timestamps)
• Source/Version control system that preserves timestamps (e.g. Subversion with use-commit-times=yes)

Proposed Feature

Either add IfDifferent mode, or make the Always mode behave that way (as e.g. discussed here: #7654 (comment))