From: Willy Tarreau <w@1wt.eu>
Date: Tue, 4 Feb 2020 12:50:36 +0000 (+0100)
Subject: SCRIPTS: add a new "backport" script to simplify long series of backports
X-Git-Tag: v2.2-dev2~42
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e77a13aa3f82f70e9f82e712287390d500bd0c8b;p=thirdparty%2Fhaproxy.git

SCRIPTS: add a new "backport" script to simplify long series of backports

The script is simply called from the repository holding the patch to
backport, with the last branch number and the commit(s) ID(s) to send
there and it then follows the chain of "down" repos to go down one step
until it meets the indicated last one. It basically automates what we do
by hand. Example:

   ./scripts/backport 1.9 1c7c0d6b97513e79c304aaf834f83843f32a674d

Note that it does *not* push, which still has to be done by hand after
building and testing.
---

diff --git a/scripts/backport b/scripts/backport
new file mode 100755
index 0000000000..c87665136e
--- /dev/null
+++ b/scripts/backport
@@ -0,0 +1,146 @@
+#!/bin/bash
+
+USAGE="Usage: ${0##*/} <last> <commit> [...]"
+START="$PWD"
+LAST=
+UPSTREAM=
+COMMIT=
+BRANCH=
+
+die() {
+	[ "$#" -eq 0 ] || echo "$*" >&2
+	exit 1
+}
+
+err() {
+	echo "$*" >&2
+}
+
+quit() {
+	[ "$#" -eq 0 ] || echo "$*"
+	exit 0
+}
+
+short() {
+	# git rev-parse --short $1
+	echo "${1::8}"
+}
+
+# returns the latest commit ID in $REPLY. Returns 0 on success, non-zero on
+# failure with $REPLY empty.
+get_last_commit() {
+	REPLY=$(git rev-parse HEAD)
+	test -n "$REPLY"
+}
+
+# returns the name of the current branch (1.8, 1.9, etc) in $REPLY. Returns 0
+# on success, non-zero on failure with $REPLY empty.
+get_branch() {
+	local major subver ext
+	REPLY=$(git describe --tags HEAD --abbrev=0 2>/dev/null)
+	REPLY=${REPLY#v}
+	subver=${REPLY#[0-9]*.[0-9]*[-.]*[0-9].}
+	[ "${subver}" != "${REPLY}" ] || subver=""
+	major=${REPLY%.$subver}
+	ext=${major#*[0-9].*[0-9]}
+	REPLY=${major%${ext}}
+	test -n "$REPLY"
+}
+
+# returns the path to the next "up" remote in $REPLY, and zero on success
+# or non-zero when the last one was reached.
+up() {
+	REPLY=$(git remote -v | awk '/^up\t.*\(fetch\)$/{print $2}')
+	test -n "$REPLY"
+}
+
+# returns the path to the next "down" remote in $REPLY, and zero on success
+# or non-zero when the last one was reached.
+down() {
+	REPLY=$(git remote -v | awk '/^down\t.*\(fetch\)$/{print $2}')
+	test -n "$REPLY"
+}
+
+# verifies that the repository is clean of any pending changes
+check_clean() {
+	test -z "$(git status -s -uno)"
+}
+
+# verifies that HEAD is the master
+check_master() {
+	test "$(git rev-parse --verify -q HEAD 2>&1)" != "$(git rev-parse --verify -q master 2>&1)"
+}
+
+# tries to switch to the master branch, only if the current one is clean. Dies on failure.
+switch_master() {
+	check_clean || die "$BRANCH: local changes, stopping on commit $COMMIT (upstream $UPSTREAM)"
+	git checkout master >/dev/null 2>&1 || die "$BRANCH: failed to checkout master, stopping on commit $COMMIT (upstream $UPSTREAM)"
+}
+
+# walk up to the first repo
+walk_up() {
+	cd "$START"
+}
+
+# updates the "up" remote repository. Returns non-zero on error.
+update_up() {
+	git remote update up >/dev/null 2>&1
+}
+
+# backports commit "$1" with a signed-off by tag. In case of failure, aborts
+# the change and returns non-zero. Unneeded cherry-picks do return an error
+# because we don't want to accidently backport the latest commit instead of
+# this one, and we don't know this one's ID.
+backport_commit() {
+	local empty=1
+
+	if ! git cherry-pick -sx "$1"; then
+		[ -n "$(git diff)" -o -n "$(git diff HEAD)" ] || empty=0
+		git cherry-pick --abort
+		return 1
+	fi
+}
+
+[ "$1" != "-h" -a "$1" != "--help" ] || quit "$USAGE"
+[ -n "$1" -a -n "$2" ] || die "$USAGE"
+
+LAST="$1"
+shift
+
+# go back to the root of the repo
+cd $(git rev-parse --show-toplevel)
+START="$PWD"
+
+while [ -n "$1" ]; do
+	UPSTREAM="$1"
+	COMMIT="$1"
+	BRANCH="-source-"
+	while :; do
+		if ! down; then
+			err "branch $BRANCH: can't go further, is repository 'down' properly set ?"
+			break
+		fi
+
+		cd "$REPLY" || die "Failed to 'cd' to '$REPLY' from '$PWD', is repository 'down' properly set ?"
+
+		check_clean || die "Local changes in $PWD, stopping before backporting commit $COMMIT (upstream $UPSTREAM)"
+
+		check_master || switch_master || die "Cannot switch to 'master' branch in $PWD, stopping before backporting commit $COMMIT (upstream $UPSTREAM)"
+		get_branch || die "Failed to get branch name in $PWD, stopping before backporting commit $COMMIT (upstream $UPSTREAM)"
+		BRANCH="$REPLY"
+
+		update_up || die "$BRANCH: failed to update repository 'up', stopping before backporting commit $COMMIT (upstream $UPSTREAM)"
+
+		backport_commit "$COMMIT" || die "$BRANCH: failed to backport commit $COMMIT (upstream $UPSTREAM). Leaving repository $PWD intact."
+
+		if [ "$BRANCH" = "$LAST" ]; then
+			# reached the stop point, don't apply further
+			break
+		fi
+
+		get_last_commit || die "$BRANCH: cannot retrieve last commit ID, stopping after backporting commit $COMMIT (upstream $UPSTREAM)"
+		COMMIT="$REPLY"
+	done
+	walk_up || die "Failed to go back to $PWD, stopping *after* backporting upstream $UPSTREAM"
+	shift
+done