Merge branch 'pw/rebase-i-merge-segv-fix'

"git rebase -i", when a 'merge <branch>' insn in its todo list
fails, segfaulted, which has been (minimally) corrected.

* pw/rebase-i-merge-segv-fix:
  rebase -i: fix SIGSEGV when 'merge <branch>' fails
  t3430: add conflicting commit

sequencer.c

@@ -2610,8 +2610,13 @@ static int error_with_patch(struct commit *commit,
 	const char *subject, int subject_len,
 	struct replay_opts *opts, int exit_code, int to_amend)
 {
-	if (make_patch(commit, opts))
-		return -1;
+	if (commit) {
+		if (make_patch(commit, opts))
+			return -1;
+	} else if (copy_file(rebase_path_message(),
+			     git_path_merge_msg(the_repository), 0666))
+		return error(_("unable to copy '%s' to '%s'"),
+			     git_path_merge_msg(the_repository), rebase_path_message());
 	if (to_amend) {
 		if (intend_to_amend())
@@ -2626,9 +2631,18 @@ static int error_with_patch(struct commit *commit,
 			  "\n"
 			  "  git rebase --continue\n"),
 			gpg_sign_opt_quoted(opts));
-	} else if (exit_code)
-		fprintf_ln(stderr, _("Could not apply %s... %.*s"),
-			short_commit_name(commit), subject_len, subject);
+	} else if (exit_code) {
+		if (commit)
+			fprintf_ln(stderr, _("Could not apply %s... %.*s"),
+				   short_commit_name(commit), subject_len, subject);
+		else
+			/*
+			 * We don't have the hash of the parent so
+			 * just print the line from the todo file.
+			 */
+			fprintf_ln(stderr, _("Could not merge %.*s"),
+				   subject_len, subject);
+	}
 	return exit_code;
 }

t/t3430-rebase-merges.sh

@@ -13,8 +13,10 @@ Initial setup:
     -- B --                   (first)
    /       \
  A - C - D - E - H            (master)
-       \       /
-         F - G                (second)
+   \    \       /
+    \    F - G                (second)
+     \
+      Conflicting-G
 '
 . ./test-lib.sh
 . "$TEST_DIRECTORY"/lib-rebase.sh
@@ -49,7 +51,9 @@ test_expect_success 'setup' '
 	git merge --no-commit G &&
 	test_tick &&
 	git commit -m H &&
-	git tag -m H H
+	git tag -m H H &&
+	git checkout A &&
+	test_commit conflicting-G G.t
 '
 test_expect_success 'create completely different structure' '
@@ -72,7 +76,7 @@ test_expect_success 'create completely different structure' '
 	EOF
 	test_config sequence.editor \""$PWD"/replace-editor.sh\" &&
 	test_tick &&
-	git rebase -i -r A &&
+	git rebase -i -r A master &&
 	test_cmp_graph <<-\EOF
 	*   Merge the topic branch '\''onebranch'\''
 	|\
@@ -125,7 +129,7 @@ test_expect_success '`reset` refuses to overwrite untracked files' '
 	git rebase --abort
 '
-test_expect_success 'failed `merge` writes patch (may be rescheduled, too)' '
+test_expect_success 'failed `merge -C` writes patch (may be rescheduled, too)' '
 	test_when_finished "test_might_fail git rebase --abort" &&
 	git checkout -b conflicting-merge A &&
@@ -141,13 +145,25 @@ test_expect_success 'failed `merge` writes patch (may be rescheduled, too)' '
 	: fail because of merge conflict &&
 	rm G.t .git/rebase-merge/patch &&
-	git reset --hard &&
-	test_commit conflicting-G G.t not-G conflicting-G &&
+	git reset --hard conflicting-G &&
 	test_must_fail git rebase --continue &&
 	! grep "^merge -C .* G$" .git/rebase-merge/git-rebase-todo &&
 	test_path_is_file .git/rebase-merge/patch
 '
+SQ="'"
+test_expect_success 'failed `merge <branch>` does not crash' '
+	test_when_finished "test_might_fail git rebase --abort" &&
+	git checkout conflicting-G &&
+
+	echo "merge G" >script-from-scratch &&
+	test_config sequence.editor \""$PWD"/replace-editor.sh\" &&
+	test_tick &&
+	test_must_fail git rebase -ir HEAD &&
+	! grep "^merge G$" .git/rebase-merge/git-rebase-todo &&
+	grep "^Merge branch ${SQ}G${SQ}$" .git/rebase-merge/message
+'
+
 test_expect_success 'with a branch tip that was cherry-picked already' '
 	git checkout -b already-upstream master &&
 	base="$(git rev-parse --verify HEAD)" &&