don't use short-sha

bb.edn

@@ -172,6 +172,19 @@
                 [:string {:name "description" :description "Lowercase alphanumeric/underscore name (e.g., mq_indexes)"}]]
    :task (task! (new-migration/new-migration parsed))}
 
+  backport
+  {:doc "Backport a merged PR onto release-x.<version>.x via cherry-pick"
+   :requires [[mage.backport :as backport]]
+   :examples [["./bin/mage backport 73718 55" "Cherry-pick PR #73718 onto release-x.55.x locally"]
+              ["./bin/mage backport 73718 55 --push" "...and push the backport branch"]
+              ["./bin/mage backport 73718 55 --pr" "...and push + open the backport PR via gh"]]
+   :options [["-p" "--push" "Push the backport branch to origin after a clean cherry-pick"]
+             [nil  "--pr"   "Push and open a draft PR via `gh pr create` (implies --push)"]]
+   :arg-schema [:tuple
+                [:string {:name "pr-number" :description "Merged PR number to backport"}]
+                [:string {:name "target-version" :description "Target major release (e.g. 55)"}]]
+   :task (task! (backport/backport parsed))}
+
   jar-download
   {:doc "Download (and optionally run) jar for a metabase version or branch"
    :examples [["./bin/mage jar-download 50" "Download the latest enterprise version of release 50 to ~/path/to/my/metabase/jars"]

mage/src/mage/backport.clj

@@ -0,0 +1,124 @@
+(ns mage.backport
+  "Backport a merged PR to a `release-x.<version>.x` branch via cherry-pick.
+
+  Mirrors `.github/actions/create-backport/action.yml` but runs locally:
+  looks up the PR's merge commit via `gh`, creates a `backport-<v>-<sha>`
+  branch from `origin/release-x.<v>.x`, and cherry-picks. Stops after the
+  cherry-pick — pushing and opening the PR is left to you."
+  (:require
+   [cheshire.core :as json]
+   [clojure.string :as str]
+   [mage.color :as c]
+   [mage.shell :as shell]))
+
+(set! *warn-on-reflection* true)
+
+(defn- die! [msg]
+  (println (c/red msg))
+  #_{:clj-kondo/ignore [:discouraged-java-method]}
+  (System/exit 1))
+
+(defn- working-tree-clean?
+  "Tracked tree is clean (untracked files are fine — they survive checkouts)."
+  []
+  (and (zero? (:exit (shell/sh* {:quiet? true} "git" "diff" "--quiet")))
+       (zero? (:exit (shell/sh* {:quiet? true} "git" "diff" "--cached" "--quiet")))))
+
+(defn- current-branch []
+  (str/trim (first (shell/sh {:quiet? true} "git" "rev-parse" "--abbrev-ref" "HEAD"))))
+
+(defn- ref-exists? [ref]
+  (zero? (:exit (shell/sh* {:quiet? true} "git" "rev-parse" "--verify" "--quiet" ref))))
+
+(defn- gh-pr-info [pr-number]
+  (let [{:keys [exit out err]} (shell/sh* {:quiet? true}
+                                          "gh" "pr" "view" (str pr-number)
+                                          "--json" "number,title,mergeCommit,state,author")]
+    (when-not (zero? exit)
+      (die! (str "gh pr view failed: " (str/join "\n" (concat out err)))))
+    (json/parse-string (str/join "\n" out) true)))
+
+(defn backport
+  "Cherry-pick a merged PR onto a release branch."
+  [{:keys [arguments options]}]
+  (let [[pr-number-str target-version-str] arguments
+        pr-number      (parse-long pr-number-str)
+        target-version (parse-long target-version-str)
+        target-branch  (format "release-x.%d.x" target-version)
+        remote-ref     (str "origin/" target-branch)
+        open-pr?       (boolean (:pr options))
+        push?          (or open-pr? (boolean (:push options)))]
+    (when-not (working-tree-clean?)
+      (die! "Working tree has uncommitted/staged changes. Commit or stash them first."))
+    (println (c/green (format "Fetching origin (looking for %s)..." target-branch)))
+    (shell/sh "git" "fetch" "origin" target-branch)
+    (when-not (ref-exists? remote-ref)
+      (die! (format "%s does not exist on origin." target-branch)))
+    (let [{:keys [title state mergeCommit author]} (gh-pr-info pr-number)
+          commit       (:oid mergeCommit)
+          author-login (:login author)]
+      (when-not (= state "MERGED")
+        (die! (format "PR #%d is %s, not MERGED. Refusing to backport." pr-number state)))
+      (when-not commit
+        (die! (format "Could not determine merge commit for PR #%d." pr-number)))
+      (let [backport-branch (format "backport-%d-%s" target-version commit)
+            saved-branch    (current-branch)
+            gh-title        (format "🤖 backported \"%s\"" title)
+            gh-body         (str "#" pr-number)
+            assignee        (or author-login "@me")]
+        (when (ref-exists? backport-branch)
+          (die! (format "Branch %s already exists locally. Delete it (git branch -D %s) and retry."
+                        backport-branch backport-branch)))
+        (println (c/cyan (format "PR #%d: %s" pr-number title)))
+        (println (c/cyan (format "Merge commit: %s" commit)))
+        (println (c/cyan (format "Creating %s from %s..." backport-branch remote-ref)))
+        (shell/sh "git" "checkout" "-B" backport-branch remote-ref)
+        (println (c/cyan (format "Cherry-picking %s..." commit)))
+        (let [{:keys [exit]} (shell/sh* "git" "cherry-pick" commit)]
+          (if (zero? exit)
+            (do
+              (println (c/green (format "✓ Clean cherry-pick onto %s." backport-branch)))
+              (if push?
+                (do
+                  (println (c/cyan (format "Pushing %s to origin..." backport-branch)))
+                  (shell/sh "git" "push" "-u" "origin" backport-branch))
+                (do
+                  (println (c/yellow "Skipping push (pass --push or --pr to do it automatically)."))
+                  (println (format "  git push -u origin %s" backport-branch))))
+              (if open-pr?
+                (do
+                  (println (c/cyan "Opening backport PR..."))
+                  (shell/sh "gh" "pr" "create"
+                            "--base" target-branch
+                            "--head" backport-branch
+                            "--label" "was-backported"
+                            "--assignee" assignee
+                            "--title" gh-title
+                            "--body" gh-body))
+                (when-not open-pr?
+                  (println (c/yellow "Skipping PR creation (pass --pr to do it automatically)."))
+                  (println (format "  gh pr create --base %s --head %s \\"
+                                   target-branch backport-branch))
+                  (println (format "    --label was-backported --assignee %s \\" assignee))
+                  (println (format "    --title %s \\" (pr-str gh-title)))
+                  (println (format "    --body %s" (pr-str gh-body)))))
+              (println (c/cyan (format "Returning to %s..." saved-branch)))
+              (shell/sh "git" "checkout" saved-branch)
+              (println (c/green (format "✓ Done. Backport branch: %s" backport-branch))))
+            (do
+              (println)
+              (println (c/yellow (format "Cherry-pick produced conflicts on %s. Resolve them, then:"
+                                         backport-branch)))
+              (println "  git add <files>")
+              (println "  git cherry-pick --continue")
+              (println (format "  git push -u origin %s" backport-branch))
+              (println (format "  gh pr create --base %s --head %s \\"
+                               target-branch backport-branch))
+              (println (format "    --label was-backported --assignee %s \\" assignee))
+              (println (format "    --title %s \\" (pr-str gh-title)))
+              (println (format "    --body %s" (pr-str gh-body)))
+              (println)
+              (println (c/yellow "To abort and return to your previous branch:"))
+              (println "  git cherry-pick --abort")
+              (println (format "  git checkout %s" saved-branch))
+              (println (format "  git branch -D %s" backport-branch)))))))))