format-patch: notice failure to open cover letter for writing

The make_cover_letter() function is supposed to open a new file for writing, and let the caller write into it via FILE *rev->diffopt.file but because the function does not return anything, the caller does not bother checking the return value. Make sure it dies, instead of keep going with a NULL output filestream and relying on it to cause a crash, when it fails to open the file. Signed-off-by: Junio C Hamano <gitster@pobox.com>

Junio C Hamano committed Feb 22, 2019 at 11:26 UTC 2fe95f494cde6cb3c3e6894bb687961b28b1764b
2 files changed +7 -1
builtin/log.c
+1 -1
@@ -1050,7 +1050,7 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
1050
1051 if (!use_stdout &&
1052 open_next_file(NULL, rev->numbered_files ? NULL : "cover-letter", rev, quiet))
1053 - return;
1053 + die(_("failed to create cover-letter file"));
1054
1055 log_write_email_headers(rev, head, &pp.after_subject, &need_8bit_cte, 0);
1056
t/t4014-format-patch.sh
+6
@@ -589,6 +589,12 @@ test_expect_success 'excessive subject' '
589 ls patches/0004-This-is-an-excessively-long-subject-line-for-a-messa.patch
590 '
591
592 +test_expect_success 'failure to write cover-letter aborts gracefully' '
593 + test_when_finished "rmdir 0000-cover-letter.patch" &&
594 + mkdir 0000-cover-letter.patch &&
595 + test_must_fail git format-patch --no-renames --cover-letter -1
596 +'
597 +
598 test_expect_success 'cover-letter inherits diff options' '
599 git mv file foo &&
600 git commit -m foo &&