How to deal with files that are relevant to version control, but that frequently change in irrelevant ways?

In our case, it's rare for a developer to make a meaningful change to the .bdsproj, .dpr, .res files. So we reject the commit (pre-commit hook in subversion) unless special tags: [add project file] or [add res file] are present in the commit comment. This prevents "frivilous" changes to those files.

SVN/git cannot "know" which bits of the file are important, and translating what is important for you to commit or not into file "bits" would be difficult (especially when you don't know exactly how the information is structured within it). The most practical solution is to check the changes that have been made to the file and decide whether to commit them or not to the repository.

You can decide which bits of the file you want to commit with git. This is not, however, the automated process you seem to be looking for.

For the specific case of startparameters: the DDevExtentions plugin of the well known Andreas Hausladen allow for the start parameters be stored separetely of dproj file. See more details about DDevExtensions on his site.

EDIT: If I remember correctly, this feature was created just because he had that exact problem with start parameters and version control.