Fix XMP files updating needlessly

[wpferguson]

src/common/image.c - don't force XMP writes

Fixes #18138

[jenshannoschwalm]

On first-sight this looked wrong to me :-) But indeed this just enforces the g_compute_checksum_for_data check in dt_exif_xmp_write to be taken into account so indeed it's right :-)

I think the force_write flag is somewhat misleading as we now always call dt_exif_xmp_write with FALSE. Wouldn't it be better to simplify code and api and remove that flag?

[wpferguson]

Force write also forces all the darktable tags to be written to the XMP file, which is why I changed it to TRUE in image.c. What I didn't know/realize was that it would cause the XMP to be written every time the image was closed from darkroom.

For 5.0.1 I think we should just revert my earlier change.

For 5.2 we can look at the whole function and decide what needs to happen , i.e. should all darktable tags be preset in the XMP and/or how do we do it if we decide they don't? IMO if we are using the XMP files as the database backup of last resort, then all of the darktable tags should be present. If some of the darktable tags don't need to be present in the XMP, then why are we using them in the first place.

[TurboGit]

Thanks!

[TurboGit]

Merged in master and 5.0.x branch.