trailer --only-input: prefer "configuration variables" over "rules"

Use the phrase "configuration variables" instead of "rules" because

(1) we already say "configuration variables" in multiple
    places in the docs (where the word "rules" is only used for describing
    "--only-input" behavior and for an unrelated case of mentioning how
    the trailers do not follow "rules for RFC 822 headers"), and

(2) this phrase is more specific than just "rules".

Signed-off-by: Linus Arver <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: Linus Arver

Documentation/git-interpret-trailers.txt

@@ -149,8 +149,8 @@ OPTIONS
 
 --only-input::
 	Output only trailers that exist in the input; do not add any
-	from the command-line or by following configured `trailer.*`
-	rules.
+	from the command-line or by applying `trailer.*` configuration
+	variables.
 
 --unfold::
 	Remove any whitespace-continuation in trailers, so that each

builtin/interpret-trailers.c

@@ -105,7 +105,7 @@ int cmd_interpret_trailers(int argc, const char **argv, const char *prefix)
 			     N_("action if trailer is missing"), option_parse_if_missing),
 
 		OPT_BOOL(0, "only-trailers", &opts.only_trailers, N_("output only the trailers")),
-		OPT_BOOL(0, "only-input", &opts.only_input, N_("do not apply config rules")),
+		OPT_BOOL(0, "only-input", &opts.only_input, N_("do not apply trailer.* configuration variables")),
 		OPT_BOOL(0, "unfold", &opts.unfold, N_("join whitespace-continued values")),
 		OPT_CALLBACK_F(0, "parse", &opts, NULL, N_("alias for --only-trailers --only-input --unfold"),
 			PARSE_OPT_NOARG | PARSE_OPT_NONEG, parse_opt_parse),