feat(save): add an atomic conflict gate for enum and relation fields

The text conflict gate (pearl--resolve-conflict) is built for mergeable text — it can open an smerge buffer, stash to the kill ring, and advance a SHA hash. None of that fits a state, priority, assignee, or label conflict, where the value is a single id or scalar that can't be combined.

pearl--resolve-atomic-conflict is the sibling for those fields: it prompts use-local / use-remote / cancel (no merge option), and delegates the actual push and the baseline advance to the caller's two callbacks, so it stays free of any field-specific mechanics. It maps to the same outcome contract as the text gate — cancel to conflict/cancelled, use-local to pushed or failed/push-failed, use-remote to resolved-remote.

It's not wired into a saver yet — the per-field savers in the next commit call it.

2 files changed, 102 insertions, 0 deletions

diff --git a/pearl.el b/pearl.el
index abd0166..7d2210e 100644
--- a/pearl.el
+++ b/pearl.el
@@ -2081,6 +2081,52 @@ push-failed), `rewrite' abort -> (conflict aborted)."
                      (when outcome-cb (funcall outcome-cb 'failed 'push-failed))))))
       (lambda () (when outcome-cb (funcall outcome-cb 'conflict 'aborted)))))))
 
+(defun pearl--read-atomic-conflict-resolution (label)
+  "Prompt for resolving an atomic-field conflict on LABEL, returning a symbol.
+One of `use-local' (push mine, overwrite Linear), `use-remote' (take Linear's),
+or `cancel'.  There is no merge option -- an enum or relation value can't be
+combined.  A bare RET defaults to `cancel'."
+  (let* ((choices '(("cancel -- leave the field in conflict" . cancel)
+                    ("use local -- push my value, overwrite Linear" . use-local)
+                    ("use remote -- take Linear's value" . use-remote)))
+         (default (caar choices))
+         (pick (completing-read
+                (format "Conflict on %s (RET cancels): " label)
+                (mapcar #'car choices) nil t nil nil default)))
+    (cdr (assoc pick choices))))
+
+(defun pearl--resolve-atomic-conflict
+    (label local-display remote-display push-local-fn take-remote-fn outcome-cb)
+  "Resolve an atomic-field (enum/relation) conflict on LABEL interactively.
+The sibling of `pearl--resolve-conflict' for fields whose value is a single
+id or scalar, not mergeable text -- so there is no smerge/rewrite branch and no
+SHA hash is written.
+
+LOCAL-DISPLAY and REMOTE-DISPLAY are human-readable values for the prompt.
+PUSH-LOCAL-FN takes a callback invoked with non-nil on a successful push of the
+local value (the caller advances the baseline on success).  TAKE-REMOTE-FN
+adopts Linear's value locally and advances the baseline, with no push.
+OUTCOME-CB is called once with (STATUS REASON): `cancel' -> (conflict
+cancelled); `use-local' -> (pushed nil) or (failed push-failed); `use-remote'
+-> (resolved-remote nil)."
+  (pcase (pearl--read-atomic-conflict-resolution label)
+    ('cancel
+     (message "Left %s in conflict (refresh to see Linear's %s)" label remote-display)
+     (funcall outcome-cb 'conflict 'cancelled))
+    ('use-local
+     (funcall push-local-fn
+              (lambda (ok)
+                (if ok
+                    (progn
+                      (message "Pushed your %s (%s) to Linear" label local-display)
+                      (funcall outcome-cb 'pushed nil))
+                  (message "Failed to push %s" label)
+                  (funcall outcome-cb 'failed 'push-failed)))))
+    ('use-remote
+     (funcall take-remote-fn)
+     (message "Took Linear's %s (%s)" label remote-display)
+     (funcall outcome-cb 'resolved-remote nil))))
+
 ;;; Compose Buffer
 ;;
 ;; A focused Org buffer for composing multi-line text (comments, descriptions)
diff --git a/tests/test-pearl-conflict.el b/tests/test-pearl-conflict.el
index 138e622..56d3c84 100644
--- a/tests/test-pearl-conflict.el
+++ b/tests/test-pearl-conflict.el
@@ -224,6 +224,62 @@
           (should (string= (secure-hash 'sha256 "merged text")
                            (org-entry-get marker "LINEAR-DESC-SHA256"))))))))
 
+;;; --resolve-atomic-conflict (enum/relation fields, no merge)
+
+(ert-deftest test-pearl-resolve-atomic-conflict-cancel ()
+  "Cancel pushes nothing, takes nothing, and reports conflict/cancelled."
+  (let (pushed took outcome)
+    (cl-letf (((symbol-function 'pearl--read-atomic-conflict-resolution)
+               (lambda (_) 'cancel)))
+      (pearl--resolve-atomic-conflict
+       "ENG-1 state" "In Progress" "Done"
+       (lambda (cb) (setq pushed t) (funcall cb t))
+       (lambda () (setq took t))
+       (lambda (status reason) (setq outcome (list status reason))))
+      (should-not pushed)
+      (should-not took)
+      (should (equal '(conflict cancelled) outcome)))))
+
+(ert-deftest test-pearl-resolve-atomic-conflict-use-local-pushes ()
+  "Use-local runs the push; on success reports pushed."
+  (let (pushed took outcome)
+    (cl-letf (((symbol-function 'pearl--read-atomic-conflict-resolution)
+               (lambda (_) 'use-local)))
+      (pearl--resolve-atomic-conflict
+       "ENG-1 state" "In Progress" "Done"
+       (lambda (cb) (setq pushed t) (funcall cb t))
+       (lambda () (setq took t))
+       (lambda (status reason) (setq outcome (list status reason))))
+      (should pushed)
+      (should-not took)
+      (should (equal '(pushed nil) outcome)))))
+
+(ert-deftest test-pearl-resolve-atomic-conflict-use-local-push-failure ()
+  "A failed local push reports failed/push-failed."
+  (let (outcome)
+    (cl-letf (((symbol-function 'pearl--read-atomic-conflict-resolution)
+               (lambda (_) 'use-local)))
+      (pearl--resolve-atomic-conflict
+       "ENG-1 state" "In Progress" "Done"
+       (lambda (cb) (funcall cb nil))
+       (lambda () nil)
+       (lambda (status reason) (setq outcome (list status reason))))
+      (should (equal '(failed push-failed) outcome)))))
+
+(ert-deftest test-pearl-resolve-atomic-conflict-use-remote-takes-no-push ()
+  "Use-remote adopts Linear's value, never pushes, and reports resolved-remote."
+  (let (pushed took outcome)
+    (cl-letf (((symbol-function 'pearl--read-atomic-conflict-resolution)
+               (lambda (_) 'use-remote)))
+      (pearl--resolve-atomic-conflict
+       "ENG-1 state" "In Progress" "Done"
+       (lambda (cb) (setq pushed t) (funcall cb t))
+       (lambda () (setq took t))
+       (lambda (status reason) (setq outcome (list status reason))))
+      (should took)
+      (should-not pushed)
+      (should (equal '(resolved-remote nil) outcome)))))
+
 ;;; --conflict-has-markers-p
 
 (ert-deftest test-pearl-conflict-has-markers-p ()