Add script to cut release branch (#2567)

Summary:
Pull Request resolved: #2567

Step 1 of release process: Create a release branch.

The branch is named with `release/MAJOR.MINOR`.

From executorch root, run `./scripts/release/cut-release-branch.sh` will cut a release branch off stable branch (`viable/strict`) by default. Use `GIT_BRANCH_TO_CUT_FROM=main ./scripts/release/cut-release-branch.sh` to cut off `main` branch.

imported-using-ghimport

Test Plan: Imported from OSS

Reviewed By: huydhn

Differential Revision: D55208762

Pulled By: guangy10

fbshipit-source-id: cdf676586266b475a74d42c1ef31f93122657925

Author: guangy10

scripts/release/cut-release-branch.sh

@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+: '
+So you are looking to cut a release branch? Well you came
+to the right script.
+
+This script can be used to cut any branch on any repository
+
+For `pytorch/executorch` usage would be like:
+> DRY_RUN=disabled ./scripts/release/cut-release-branch.sh
+
+or to cut from main branch:
+> DRY_RUN=disabled GIT_BRANCH_TO_CUT_FROM=main ./scripts/release/cut-release-branch.sh
+'
+
+set -eou pipefail
+
+GIT_TOP_DIR=$(git rev-parse --show-toplevel)
+GIT_REMOTE=${GIT_REMOTE:-origin}
+GIT_BRANCH_TO_CUT_FROM=${GIT_BRANCH_TO_CUT_FROM:-viable/strict}
+
+# should output something like 1.11
+RELEASE_VERSION=${RELEASE_VERSION:-$(cut -d'.' -f1-2 "${GIT_TOP_DIR}/version.txt")}
+
+DRY_RUN_FLAG="--dry-run"
+if [[ ${DRY_RUN:-enabled} == "disabled" ]]; then
+    DRY_RUN_FLAG=""
+fi
+
+
+(
+    set -x
+    git fetch --all
+    git checkout "${GIT_REMOTE}/${GIT_BRANCH_TO_CUT_FROM}"
+)
+
+for branch in "release/${RELEASE_VERSION}" "orig/release/${RELEASE_VERSION}"; do
+    if git rev-parse --verify "${branch}" >/dev/null 2>/dev/null; then
+        echo "+ Branch ${branch} already exists, skipping..."
+        continue
+    else
+        (
+            set -x
+            git checkout "${GIT_REMOTE}/${GIT_BRANCH_TO_CUT_FROM}"
+            git checkout -b "${branch}"
+            git push -q ${DRY_RUN_FLAG} "${GIT_REMOTE}" "${branch}"
+        )
+    fi
+done

version.txt

@@ -0,0 +1 @@
+0.2.0a0