commit 102fba8b84c74851ac56ae5a99a5739e2a4b2514
from: Stefan Sperling <stsp@stsp.name>
date: Sun Mar 03 10:54:49 2024 UTC

add an xfail test for a case where rebase fails to forward a branch

Because 'got rebase' only does a first-parent traversal it will try to
rebase commits which appear in the history of a branch, even when the
branch to be rebased is already based on that history. This results in
spurious merge conflicts as existing changes get re-applied.

The desired behaviour would be that 'got rebase' forwards the branch,
as it does when the 'got merge -M' command used by this test case is
replaced by a simple 'got merge' which avoids creating a merge commit.

Problem reported by naddy in the "Landry's firefox repository" thread:
https://marc.gameoftrees.org/mail/1706721001.20565_0.html

commit - 4cbe2b468089c3a0d8cc4963ef0056060b82049a
commit + 102fba8b84c74851ac56ae5a99a5739e2a4b2514
blob - 2054bedb08f8feba973a66370ee61cbc6fb10ed8
blob + 46f11f7c161db17549ba3c6ba4055ffcc81b97ce
--- regress/cmdline/rebase.sh
+++ regress/cmdline/rebase.sh
@@ -2185,7 +2185,73 @@ test_rebase_across_merge_commit() {
 
 	test_done "$testroot" 0
 }
+
+test_rebase_merged_history_traversal() {
+	local testroot=`test_init rebase_merged_history_traversal`
+	local commit0=`git_show_branch_head $testroot/repo master`
+
+	if ! got checkout $testroot/repo $testroot/wt >/dev/null; then
+		test_done "$testroot" 1
+		return 1
+	fi
 
+	(cd $testroot/wt && got branch -c $commit0 newbranch1) >/dev/null
+	echo "modified alpha on newbranch1" >$testroot/wt/alpha
+	(cd $testroot/wt && got commit -m 'edit alpha') >/dev/null
+	(cd $testroot/wt && got update) >/dev/null
+	local commit2=`git_show_branch_head $testroot/repo master`
+
+	echo "modified alpha on newbranch1 again" >$testroot/wt/alpha
+	(cd $testroot/wt && got commit -m 'edit alpha again') >/dev/null
+	(cd $testroot/wt && got update) >/dev/null
+	local commit3=`git_show_branch_head $testroot/repo newbranch1`
+
+	echo -n '' > $testroot/stderr.expected
+
+	(cd $testroot/wt && got update -b master) >/dev/null
+	(cd $testroot/wt && got merge -M newbranch1 >$testroot/stdout \
+		2> $testroot/stderr)
+	ret=$?
+	if [ $ret -ne 0 ]; then
+		echo "merge command failed unexpectedly" >&2
+		diff -u $testroot/stderr.expected $testroot/stderr
+		test_done "$testroot" "1"
+		return 1
+	fi
+
+	local merge_commit=`git_show_head $testroot/repo`
+
+	echo "G  alpha" > $testroot/stdout.expected
+	echo -n "Merged refs/heads/newbranch1 into refs/heads/master: " \
+		>> $testroot/stdout.expected
+	echo $merge_commit >> $testroot/stdout.expected
+	if ! cmp -s $testroot/stdout.expected $testroot/stdout; then
+		diff -u $testroot/stdout.expected $testroot/stdout
+		test_done "$testroot" 1
+		return 1
+	fi
+
+	echo "modified delta on master" >$testroot/wt/gamma/delta
+	(cd $testroot/wt && got commit -m 'edit delta') >/dev/null
+	local commit1=`git_show_branch_head $testroot/repo master`
+
+	(cd $testroot/wt && got branch newbranch2) >/dev/null
+	(cd $testroot/wt && got rebase newbranch1) > $testroot/stdout \
+		2> $testroot/stderr
+
+	echo "Forwarding refs/heads/newbranch1 to commit $commit1" > \
+		$testroot/stdout.expected
+	echo "Switching work tree to refs/heads/newbranch1" \
+		>> $testroot/stdout.expected
+
+	if ! cmp -s $testroot/stdout.expected $testroot/stdout; then
+		#diff -u $testroot/stdout.expected $testroot/stdout
+		ret="xfail ($(head -n1 $testroot/stdout))"
+	fi
+
+	test_done "$testroot" "$ret"
+}
+
 test_parseargs "$@"
 run_test test_rebase_basic
 run_test test_rebase_ancestry_check
@@ -2210,3 +2276,4 @@ run_test test_rebase_out_of_date2
 run_test test_rebase_one_commit
 run_test test_rebase_merge_commit
 run_test test_rebase_across_merge_commit
+run_test test_rebase_merged_history_traversal