cli: consider files vanishing during notmuch new non-fatal

If some software other than notmuch new renames or removes files
during the notmuch new scan (specifically after scandir but before
indexing the file), keep going instead of bailing out. Failing to
index the file is just a race condition between notmuch and the other
software; the rename could happen after the notmuch new scan
anyway. It's not fatal, and we'll catch the renamed files on the next
scan.

Add a new exit code for when files vanished, so the caller has a
chance to detect the race and re-run notmuch new to recover.

Reported by Paul Wise <pabs@debian.org> at
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=843127

2 files changed, 23 insertions, 3 deletions

diff --git a/notmuch-client.h b/notmuch-client.h
index 9ce2aef1..793f32ec 100644
--- a/notmuch-client.h
+++ b/notmuch-client.h
@@ -25,6 +25,7 @@
 #define _GNU_SOURCE /* for getline */
 #endif
 #include <stdio.h>
+#include <sysexits.h>
 
 #include "compat.h"
 
@@ -114,6 +115,16 @@ chomp_newline (char *str)
 	str[strlen(str)-1] = '\0';
 }
 
+/* Exit status code indicating temporary failure; user is invited to
+ * retry.
+ *
+ * For example, file(s) in the mail store were removed or renamed
+ * after notmuch new scanned the directories but before indexing the
+ * file(s). If the file was renamed, the indexing might not be
+ * complete, and the user is advised to re-run notmuch new.
+ */
+#define NOTMUCH_EXIT_TEMPFAIL EX_TEMPFAIL
+
 /* Exit status code indicating the requested format version is too old
  * (support for that version has been dropped).  CLI code should use
  * notmuch_exit_if_unsupported_format rather than directly exiting
diff --git a/notmuch-new.c b/notmuch-new.c
index c55dea7b..cc680b41 100644
--- a/notmuch-new.c
+++ b/notmuch-new.c
@@ -53,6 +53,7 @@ typedef struct {
     int total_files;
     int processed_files;
     int added_messages, removed_messages, renamed_messages;
+    int vanished_files;
     struct timeval tv_start;
 
     _filename_list_t *removed_files;
@@ -280,11 +281,13 @@ add_file (notmuch_database_t *notmuch, const char *filename,
     case NOTMUCH_STATUS_FILE_NOT_EMAIL:
 	fprintf (stderr, "Note: Ignoring non-mail file: %s\n", filename);
 	break;
-    /* Fatal issues. Don't process anymore. */
     case NOTMUCH_STATUS_FILE_ERROR:
+	/* Someone renamed/removed the file between scandir and now. */
+	state->vanished_files++;
 	fprintf (stderr, "Unexpected error with file %s\n", filename);
 	(void) print_status_database ("add_file", notmuch, status);
-	goto DONE;
+	break;
+    /* Fatal issues. Don't process anymore. */
     case NOTMUCH_STATUS_READ_ONLY_DATABASE:
     case NOTMUCH_STATUS_XAPIAN_EXCEPTION:
     case NOTMUCH_STATUS_OUT_OF_MEMORY:
@@ -1151,5 +1154,11 @@ notmuch_new_command (notmuch_config_t *config, int argc, char *argv[])
     if (!no_hooks && !ret && !interrupted)
 	ret = notmuch_run_hook (db_path, "post-new");
 
-    return ret || interrupted ? EXIT_FAILURE : EXIT_SUCCESS;
+    if (ret || interrupted)
+	return EXIT_FAILURE;
+
+    if (add_files_state.vanished_files)
+	return NOTMUCH_EXIT_TEMPFAIL;
+
+    return EXIT_SUCCESS;
 }