Re: Re* [RFH] adding test coverage for contrib/ in CI jobs

Junio C Hamano [off-list ref] writes:

Unfortunately, this seems to reveal existing other problems with
subtree tests (t7900), in addition to diff-highlight tests (t9400)
in various configurations.

https://github.com/git/git/actions/runs/21617099884

This Ci run is near the tip of 'seen', so there may be breakages
attributable to new topics in flight

At least some of the subtree failures on linux-reftable, such as

<https://github.com/git/git/actions/runs/21617099884/job/62298228602#step:10:421>

are actually due to a bug in ubuntu:rolling's "dirname" implementation. 
This was fixed upstream in late January [1].

bug behavior demo:

     podman run --rm -it -q docker.io/library/ubuntu:questing-20251217 \
       dirname whatever/.

outputs "whatever"

     podman run --rm -it -q docker.io/library/ubuntu:25.10 \
       dirname whatever/.

outputs "."


subtree has an up-front call to

     dir="$(dirname "$arg_prefix/.")"

which encounters the defect. It then attempts to do things like

     git read-tree --prefix=. $someref

that error out with messages like "error: invalid path './sub1'"


[1]: https://github.com/uutils/coreutils/issues/10508