This is the Linux kernel part of the EPIC Linux project, serving as upstream for ia64 Linux kernels since its deletion in Linus' tree in 6.7.
To distinguish from Linus' mainline, releases have an additional suffix of -epic[n]. Usually, the first RC is tagged with -epic1, and further versions are tagged with -epic2, -epic3 and so on. Both directly commited ia64 chages and merges from other trees bump up the epic number when tagged.
We try to merge any substantial changes from a separate branch. For efficiency purposes, this excludes simple replays and reverts after merges from Linus' tree. Any merge conflicts are described in the merge commit.
Usually, two merges from Linus' tree are done in a release cycle: one early (usualy -rc1, sometimes later RC) - most breaking changes needing replays, reverts, and sometimes migration to new APIs happen there, and one for the final tagged release.
The following distributions take this kernel tree in one form or another:
Up to 6.12, the tree was rebased on top of Linus' tree every once in a while (not every release), which meant rewriting history and the ia64 patches changing commit IDs every release, at the benefit of having a linear history with respect to Linus' tree.
Starting with 6.16, this model was replaced by a regular merge model, where Linus' tree is treated as just another downstream repo from where merges are done. That means that the history is clean since the 6.12 rebase.
Up to 7.1, merges did not have a full description (inclusion of downstream tree link and conflicts).