Add jane/pull-flambda-patches script

jane/pull-flambda-patches

@@ -0,0 +1,47 @@
+#!/bin/bash
+
+set -e
+repo="$(git rev-parse --show-toplevel)"
+cd "$repo"
+
+if ! git diff --quiet; then
+    echo "Working directory must be clean before using this script,"
+    echo "but currently has the following changes:"
+    git diff --stat
+    exit 1
+fi
+
+configure_remote () {
+    name="$1"
+    url="$2"
+    set +e
+    curr="$(git remote get-url "$name" 2>/dev/null)"
+    err=$?
+    set -e
+    if [ $err = 2 ]; then
+        git remote add "$name" "$url"
+    elif [ "$curr" != "$url" ]; then
+        {
+            echo "Error: remote $name should point to $url, not $curr"
+            echo "Try 'git remote rm $name'." 
+        } 1>&2
+        exit 1
+    fi
+}
+
+configure_remote origin 'git@github.com:janestreet/ocaml-jst'
+configure_remote flambda-backend 'git@github.com:ocaml-flambda/flambda-backend'
+configure_remote ocaml 'git@github.com:ocaml/ocaml'
+
+git fetch -q origin
+git fetch -q flambda-backend
+
+git checkout -q flambda-backend/main
+rev=$(git subtree split -P ocaml --annotate='flambda-backend: ' flambda-backend/main)
+git push -q origin $rev:refs/heads/flambda-patches |& sed '/^remote: /d'
+git checkout -q -
+
+count=$(git rev-list HEAD..origin/flambda-patches | wc -l)
+echo "$count new patches:"
+git --no-pager log --oneline HEAD..origin/flambda-patches
+git merge --no-ff -m 'Merge flambda-backend changes' origin/flambda-patches