Document per-version branch model on main README

With the scoutfs-build multi-version pipeline landing, each
supported scoutfs version (v1.28, v1.29, v1.30) has its own
long-lived branch here.  The tag history section is replaced by a
table showing which branch targets which scoutfs version, and the
rebase-for-new-upstream walkthrough is updated to describe creating
a new branch rather than overwriting main.

README.md

@@ -2,12 +2,12 @@
 
 Observer-only file access notifications for [ScoutFS](https://github.com/versity/scoutfs),
 distributed as a rebasable `git format-patch` series plus a small Go
-userspace relay daemon.  Layers onto each upstream release with minimal
-maintenance.
+userspace relay daemon.  Maintained as one long-lived branch per
+currently-supported upstream scoutfs version.
 
 ## What the series adds
 
-Three patches against the scoutfs source tree:
+Three patches against each supported scoutfs release:
 
 1. **Kmod core** — a per-mount 64 KiB ring of 64-byte notification records and
    a single-reader drain ioctl (`SCOUTFS_IOC_READ_NOTIFY`, nr 25).  Emit is
@@ -25,58 +25,67 @@ Three patches against the scoutfs source tree:
    clients.  Pure-stdlib Go; no external module dependencies.  Shipped
    with a systemd template unit `scoutfs-notifyd@<mountpoint>.service`.
 
-## Base
+The notify ABI (`SCOUTFS_IOC_READ_NOTIFY` nr 25, 64-byte event record) is
+identical across all three supported scoutfs versions, so consumers and
+the daemon do not need per-version branching in their own code.
 
-Currently rebased against:
+## Repository layout
 
-    scoutfs v1.30
+Each supported scoutfs version lives on its own long-lived branch.  The
+patches in each branch are tuned for that specific scoutfs tree; they do
+NOT apply cross-version without rebasing.
 
-See [base.txt](./base.txt).
+| Branch         | Targets scoutfs | Tag              |
+|----------------|-----------------|------------------|
+| `v1.28`        | `v1.28`         | `v1.28-notify-1` |
+| `v1.29`        | `v1.29`         | `v1.29-notify-1` |
+| `main` / `v1.30` | `v1.30`       | `v1.30-notify-1` |
 
-## Build dependencies added
-
-On top of the stock scoutfs build requirements, patch 3 adds:
-
-* `golang >= 1.26` on the build host (fetched from go.dev by the CI; no distro currently packages 1.26).
-  
-
-The Go build is offline (`GOPROXY=off`) — no network access required at
-build time.  `CGO_ENABLED=0` so the produced binary is a pure-Go static
-ELF.
+`main` tracks the newest supported scoutfs version.  When a new scoutfs
+release ships, a new branch is created and the patches are rebased onto
+it; when a scoutfs version ages out of support, its branch stays in the
+repo for historical builds but is no longer maintained.
 
 ## Applying
 
+Against a scoutfs git working tree at the matching upstream tag:
+
 ```sh
-./apply.sh /path/to/scoutfs
+git clone -b v1.29 https://git.anomalous.dev/alphacentri/scoutfs-notify.git /tmp/notify
+/tmp/notify/apply.sh /path/to/scoutfs-v1.29-checkout
 ```
 
-Runs `git am --3way` on each patch.  For a tarball instead of a git tree,
-loop `patch -p1 < patches/*.patch`.
+The script runs `git am --3way` on each patch in order.
 
 ## Rebasing onto a new upstream release
 
 ```sh
-git fetch --tags
-git checkout -B notify v1.30
-git am --3way patches/*.patch
-# resolve any conflicts, git am --continue
-git format-patch v1.30..notify -o patches/
-# update base.txt and commit
+# In a fresh scoutfs checkout:
+git checkout v1.31
+git checkout -b notify-v1.31
+
+# Apply the previous branch's patches (usually clean; resolve any
+# conflicts, git am --continue).
+git am --3way /path/to/scoutfs-notify-v1.30/patches/*.patch
+git format-patch v1.31..notify-v1.31 -o /tmp/new-patches/
+
+# Push a new branch + tag in this repo:
+cd /path/to/scoutfs-notify
+git checkout -b v1.31 main
+rm patches/*.patch
+cp /tmp/new-patches/*.patch patches/
+echo v1.31 > base.txt
+git commit -am 'v1.31-notify-1: rebase onto scoutfs v1.31'
+git push -u origin v1.31
+git tag v1.31-notify-1 && git push origin v1.31-notify-1
+# Fast-forward main to the new tip once you're ready to promote it.
 ```
 
-## Tag history
-
-    v1.30-notify-1   (current — rebased onto scoutfs v1.30, no code changes)
-v1.29-notify-4   (retired — last v1.29-base release)
-v1.29-notify-3   (retired — Go 1.21 toolchain)
-    v1.29-notify-2   (retired — C daemon; had latent ring-size compile bug)
-    v1.29-notify-1   (retired — shipped mount options)
-
 ## Quick smoke test after installation
 
 ```sh
 systemctl enable --now scoutfs-notifyd@mnt-scoutfs.service
-FSID=$(stat -f -c %i /mnt/scoutfs)   # or use your scoutfs cli
+FSID=$(scoutfs stat /mnt/scoutfs | awk '/fsid/ { print $2 }')
 socat - UNIX-CONNECT:/run/scoutfs/${FSID}/notify.sock | xxd | head
 # touch some files in /mnt/scoutfs in another terminal
 ```