From 5c0fc66c82d02d85b66517f79b5b9126918eeb1e Mon Sep 17 00:00:00 2001
From: Earl Warren <contact@earl-warren.org>
Date: Tue, 24 Oct 2023 18:19:30 +0200
Subject: [PATCH] use sha for origin instead of head

because the head ref may be either a branch or a reference, depending
on wether the PR was merged and the branch deleted. The SHA (either
from the head or the merged commit) always represents the most up to
date state of the PR.
---
 cascading-pr.sh | 38 +++++++++++++++++++++++---------------
 1 file changed, 23 insertions(+), 15 deletions(-)

diff --git a/cascading-pr.sh b/cascading-pr.sh
index 2e42a83..08c44a5 100755
--- a/cascading-pr.sh
+++ b/cascading-pr.sh
@@ -100,7 +100,7 @@ EOF
 }
 
 function close_pr() {
-    local direction=$1
+    local direction=destination
 
     if test "$(pr_state ${direction})" = "open"; then
 	log_info "closing $(pr_url ${direction})"
@@ -147,9 +147,14 @@ function pr_number() {
     pr $1 | jq --raw-output .number
 }
 
-function pr_head() {
+function pr_sha() {
     pr_get $1
-    pr $1 | jq --raw-output .head.ref
+    merged=$(pr $1 | jq --raw-output .merged)
+    if "$merged"; then
+	pr $1 | jq --raw-output .merge_commit_sha
+    else
+	pr $1 | jq --raw-output .head.sha
+    fi
 }
 
 function pr_merged() {
@@ -158,19 +163,20 @@ function pr_merged() {
 }
 
 function upsert_clone() {
-    local direction=$1 branch=$2 clone=$3
+    local direction=$1 ref="$2" sha="$3" clone=$4
 
-    local fetch=true
     if ! test -d $TMPDIR/$direction; then
-	git -c credential.helper="store --file=$TMPDIR/$direction.git-credentials" clone $clone -b $branch $TMPDIR/$direction
-	fetch=false
+	git -c credential.helper="store --file=$TMPDIR/$direction.git-credentials" clone $clone $TMPDIR/$direction
     fi
     (
 	cd $TMPDIR/$direction
-	git config credential.helper "store --file=$TMPDIR/$direction.git-credentials"
-	if $fetch; then
-	    git fetch origin
+	if test "$ref"; then
+	    git switch -c $direction origin/$ref
 	fi
+	if test "$sha"; then
+	    git switch -c $direction $sha
+	fi
+	git config credential.helper "store --file=$TMPDIR/$direction.git-credentials"
 	git config user.email cascading-pr@example.com
 	git config user.name cascading-pr
     )
@@ -190,7 +196,7 @@ function push() {
 	cd $TMPDIR/$direction
 	git add .
 	if git commit -m 'cascading-pr update'; then
-	    git push --force origin $branch
+	    git push --force origin $direction:$branch
 	    git rev-parse HEAD > ../$direction.sha
 	    log_info "pushed"
 	else
@@ -206,8 +212,8 @@ function wait_destination_ci() {
 }
 
 function update() {
-    upsert_clone origin ${options[origin_head]} ${options[origin_clone]}
-    upsert_clone destination ${options[destination_head]} ${options[destination_clone]}
+    upsert_clone origin "${options[origin_head]}" "${options[origin_sha]}" ${options[origin_clone]}
+    upsert_clone destination "${options[destination_head]}" "${options[destination_sha]}" ${options[destination_clone]}
     (
 	cd $TMPDIR/origin
 	${options[update]} $TMPDIR/destination $TMPDIR/destination-pr.json $TMPDIR/origin-pr.json
@@ -237,7 +243,8 @@ function finalize_options() {
     options[origin_scheme]=$(scheme ${options[origin_url]})
     options[origin_host_port]=$(host_port ${options[origin_url]})
     set_clone origin
-    options[origin_head]=$(pr_head origin)
+    options[origin_head]=
+    options[origin_sha]=$(pr_sha origin)
     options[destination_api]=${options[destination_url]}/api/v1/repos/${options[destination_repo]}
     options[destination_scheme]=$(scheme ${options[destination_url]})
     options[destination_host_port]=$(host_port ${options[destination_url]})
@@ -245,6 +252,7 @@ function finalize_options() {
     options[destination_base]=${options[destination_branch]}
     : ${options[prefix]:=${options[origin_repo]}}
     options[destination_head]=${options[prefix]}-${options[origin_pr]}
+    options[destination_sha]=
 }
 
 function run() {
@@ -274,7 +282,7 @@ function run() {
 	    else
 		log_info "PR is closed, close the cascade PR and remove the branch"
 		repo_login ${options[destination_repo]}
-		close_pr destination
+		close_pr
 	    fi
 	    ;;
 	*)