[Patch v6 5/6] notmuch-new: backup tags before database upgrade

[David Bremner]

All we do here is calculate the backup filename, and call the existing
dump routine.

Also take the opportity to add a message about being safe to
interrupt.
---
 notmuch-new.c        | 29 ++++++++++++++++++++++++++++-
 test/T530-upgrade.sh |  4 +++-
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/notmuch-new.c b/notmuch-new.c
index 82acf69..d269c7c 100644
--- a/notmuch-new.c
+++ b/notmuch-new.c
@@ -989,8 +989,35 @@ notmuch_new_command (notmuch_config_t *config, int argc, char *argv[])
 	    return EXIT_FAILURE;
 
 	if (notmuch_database_needs_upgrade (notmuch)) {
-	    if (add_files_state.verbosity >= VERBOSITY_NORMAL)
+	    time_t now = time (NULL);
+	    struct tm *gm_time = gmtime (&now);
+
+	    /* since dump files are written atomically, the amount of
+	     * harm from overwriting one within a second seems
+	     * relatively small. */
+
+	    const char *backup_name =
+		talloc_asprintf (notmuch, "%s/dump-%04d%02d%02dT%02d%02d%02d.gz",
+				 dot_notmuch_path,
+				 gm_time->tm_year + 1900,
+				 gm_time->tm_mon + 1,
+				 gm_time->tm_mday,
+				 gm_time->tm_hour,
+				 gm_time->tm_min,
+				 gm_time->tm_sec);
+
+	    if (add_files_state.verbosity >= VERBOSITY_NORMAL) {
 		printf ("Welcome to a new version of notmuch! Your database will now be upgraded.\n");
+		printf ("This process is safe to interrupt.\n");
+		printf ("Backing up tags to %s...\n", backup_name);
+	    }
+
+	    if (notmuch_database_dump (notmuch, backup_name, "",
+				       DUMP_FORMAT_BATCH_TAG, TRUE)) {
+		fprintf (stderr, "Backup failed. Aborting upgrade.");
+		return EXIT_FAILURE;
+	    }
+
 	    gettimeofday (&add_files_state.tv_start, NULL);
 	    notmuch_database_upgrade (notmuch,
 				      add_files_state.verbosity >= VERBOSITY_NORMAL ? upgrade_print_progress : NULL,
diff --git a/test/T530-upgrade.sh b/test/T530-upgrade.sh
index 67bbf31..d46e3d1 100755
--- a/test/T530-upgrade.sh
+++ b/test/T530-upgrade.sh
@@ -26,9 +26,11 @@ output=$(notmuch search path:foo)
 test_expect_equal "$output" ""
 
 test_begin_subtest "database upgrade from format version 1"
-output=$(notmuch new)
+output=$(notmuch new | sed -e 's/^Backing up tags to .*$/Backing up tags to FILENAME/')
 test_expect_equal "$output" "\
 Welcome to a new version of notmuch! Your database will now be upgraded.
+This process is safe to interrupt.
+Backing up tags to FILENAME
 Your notmuch database has now been upgraded to database format version 2.
 No new mail."
 
-- 
1.9.0