I have merged a fix for this particular problem. However, its probably not going to give you everything that you want. Let me document exactly what the fix was:

1. Passing a standard "refs/tags/tag" or "refs/heads/branch" will continue to work as before.
2. Passing a commitId in will show the list from that commit.
3. Passing a non standard like "refs/subgit/unsynced" will show the list at that commit. However, it will be shown as if the user had unreferenced the commit . For example this is what the UI looks like when I pass commits?until=refs/random/ref and refs/random/ref == 7288382abb721
   

Stash only really handles refs for branches, tags, PRs correctly from the UI to the backend. When you pass in another REF we decided to resolve it to a commit to make this change small. If you need the UI to display your ref as a ref rather than a commit then it will probably have to be raised as a suggestion.

One more thing to add is that ultimately we'd like to create (or let user create) pull request for the commit referenced by refs/subgit/unsynced/x reference.
These references are unique for the lifetime of the mirror.

Thank you for your question.

When handling "out-of-sync" mirror state (new changes has been added to SVN while mirror was disabled and those changes conflicts with new Git commits), our add-on creates "refs/subgit/unsynced" references for existing Git branches or tags that are about to be replaced by those from SVN.

Each "unsynced" reference refers to a commit and we'd like to let user navigate to that reference (so, that reference name is visible)

Each "unsynced" reference refers to a particular history of commits that, at certain point originates from the "standard" branch or tag. We'd like to let user navigate to that particular commit.

I.e., if there are two branches (one refers to A (refs/heads/x), and second refers to F (unsynced)):

A F < /refs/subgit/unsynced/x
|  |
B E
|  /
C 
|
D

We then would like to let user navigate to C (E's parent) and to F.

So an option to navigate to the history of a particular commit is vital and an option to navigate to the history of a particular reference is important.

Thank you very much for working on that feature, I'd be glad to provide more information if necessary.

For that to work smoothly we need two improvements - first is the one above (show history starting from a particular commit or from non refs/heads references) and second is ....

kitaev Will your needs be met if Stash only allows seeing the history of a particular commit? Its not 100% clear to me if you need both the commit and the ref to work or if you are trying to say you only need one to work.