Wrap the source code at 80 characters.
Align the backslashes in "nozero_config_help".
Tested with:
$ nbdkit null --filter=nozero --help
 [...]
 zeromode=<MODE>      One of 'none' (default), 'emulate',
'notrim',
                      'plugin'.
 fastzeromode=<MODE>  One of 'default', 'none', 'slow',
'ignore'.
 [...] 
Bugzilla: 
https://bugzilla.redhat.com/show_bug.cgi?id=2172516
Signed-off-by: Laszlo Ersek <lersek(a)redhat.com>
---
 filters/nozero/nozero.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/filters/nozero/nozero.c b/filters/nozero/nozero.c
index 09fd517f76f0..adcfa5a8ff01 100644
--- a/filters/nozero/nozero.c
+++ b/filters/nozero/nozero.c
@@ -98,8 +98,9 @@ nozero_config (nbdkit_next_config *next, nbdkit_backend *nxdata,
   return next (nxdata, key, value);
 }
 
-#define nozero_config_help \
-  "zeromode=<MODE>      One of 'none' (default), 'emulate',
'notrim', 'plugin'.\n" \
+#define nozero_config_help                                               \
+  "zeromode=<MODE>      One of 'none' (default), 'emulate',
'notrim',\n" \
+  "                     'plugin'.\n"                                   
 \
   "fastzeromode=<MODE>  One of 'default', 'none',
'slow', 'ignore'.\n"
 
 /* Check that desired mode is supported by plugin. */