When attempting to export an image without providing a specific platform(s)( eg: ctr i export <output.tar> <image_ref>) , ctr returns an error: ctr: content digest sha256:<hash>: not found . ctr exports default matcher platforms.Default() , uses the Only() match comparer which matches for a single platform and all its variants (IE linux/amd64 and linux/386). The index/manifest list that is pulled when using ctr i pull <image_ref>( without providing --all-platforms or --platform options) only pulls the platform that is relevant to the users machine(eg: only linux/amd64). Although the manifest contains references to different platforms only the default(host machines platform) content is pulled. The export function matches loosely against the different platformed manifests and as a result fails when attempting to retrieve manifest content that does not exist (eg: for an amd/64 machine the manifest for 386 does not exist for an image pulled, at least, without specifying it explicitly when pulling/using the all platforms option).

This commit changes the behavior to adopt strictly matching platform using platforms.DefaultStrict() which would match only with a single type of a platform (eg: only amd/64) using the OnlyStrict() match comparer when exporting without the --platform or --all-platform options. This change is similar to that introduced in this PR- #6906 which addresses a similar bug for ctr import - #6441.

Fixes: #5895

Signed-off-by: Yasin Turan [email protected]