What happens to podman import if reference is not present?

Documentation for podman import:

reference, if present, is a tag to assign to the image.

What happens to podman import if reference is not present?

Does podman save imported content from a tarball as a filesystem image? With what tag?

Here is an example:

$ podman import 758f677cf339-backup.tar
Getting image source signatures
Copying blob f49f459e4c71 done
Copying config 5bb687b1cc done
Writing manifest to image destination
Storing signatures
sha256:5bb687b1cc904a19a34bf8e63e2b1b5cc0d8400b0f2c6709ff44222176234369

Here we see that in podman import the reference is not present. How to find the tag (if any) assigned to the image?

No tag is used. For details see the following example with podman 5.1.1

Create /tmp/backup.tar

useradd test1
machinectl shell --uid test1
podman pull docker.io/library/alpine
ctr=$(podman create docker.io/library/alpine)
podman export $ctr > /tmp/backup.tar
exit

Import /tmp/backup.tar

useradd test2
machinectl shell --uid test2
img=$(podman import --quiet /tmp/backup.tar)

Inspect the image before and after tagging the image

podman image inspect $img > inspect1.json
podman image tag $img mytag
podman image inspect $img > inspect2.json
diff -u inspect1.json inspect2.json

The diff command produces this output

--- inspect1.json   2024-07-28 18:54:50.744204231 +0000
+++ inspect2.json   2024-07-28 18:56:18.719279791 +0000
@@ -2,8 +2,12 @@
      {
           "Id": "ee85a64cca8fc2eae7360f325b1d8dd32f09b408f8da5b6879c50ee6c9008e16",
           "Digest": "sha256:b4cad880b9456ed7b8dda95b5b9502e6ee59d7469f4de463fb075bb238054e6f",
-          "RepoTags": [],
-          "RepoDigests": [],
+          "RepoTags": [
+               "localhost/mytag:latest"
+          ],
+          "RepoDigests": [
+               "localhost/mytag@sha256:b4cad880b9456ed7b8dda95b5b9502e6ee59d7469f4de463fb075bb238054e6f"
+          ],
           "Parent": "",
           "Comment": "imported from tarball",
           "Created": "2024-07-28T18:54:24.838732101Z",
@@ -38,6 +42,8 @@
                     "comment": "imported from tarball"
                }
           ],
-          "NamesHistory": null
+          "NamesHistory": [
+               "localhost/mytag:latest"
+          ]
      }
 ]