trailer: add new .cmd config option

The `trailer.<token>.command` configuration variable
specifies a command (run via the shell, so it does not have
to be a single name or path to the command, but can be a
shell script), and the first occurrence of substring $ARG is
replaced with the value given to the `interpret-trailer`
command for the token in a '--trailer <token>=<value>' argument.

This has three downsides:

* The use of $ARG in the mechanism misleads the users that
the value is passed in the shell variable, and tempt them
to use $ARG more than once, but that would not work, as
the second and subsequent $ARG are not replaced.

* Because $ARG is textually replaced without regard to the
shell language syntax, even '$ARG' (inside a single-quote
pair), which a user would expect to stay intact, would be
replaced, and worse, if the value had an unmatched single
quote (imagine a name like "O'Connor", substituted into
NAME='$ARG' to make it NAME='O'Connor'), it would result in
a broken command that is not syntactically correct (or
worse).

* The first occurrence of substring `$ARG` will be replaced
with the empty string, in the command when the command is
first called to add a trailer with the specified <token>.
This is a bad design, the nature of automatic execution
causes it to add a trailer that we don't expect.

Introduce a new `trailer.<token>.cmd` configuration that
takes higher precedence to deprecate and eventually remove
`trailer.<token>.command`, which passes the value as an
argument to the command.  Instead of "$ARG", users can
refer to the value as positional argument, $1, in their
scripts. At the same time, in order to allow
`git interpret-trailers` to better simulate the behavior
of `git command -s`, 'trailer.<token>.cmd' will not
automatically execute.

Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Christian Couder <christian.couder@gmail.com>
Signed-off-by: ZheNing Hu <adlternative@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 25 insertions, 10 deletions

diff --git a/trailer.c b/trailer.c
index be4e972642..7c7cb61a94 100644
--- a/trailer.c
+++ b/trailer.c
@@ -14,6 +14,7 @@ struct conf_info {
 	char *name;
 	char *key;
 	char *command;
+	char *cmd;
 	enum trailer_where where;
 	enum trailer_if_exists if_exists;
 	enum trailer_if_missing if_missing;
@@ -127,6 +128,7 @@ static void free_arg_item(struct arg_item *item)
 	free(item->conf.name);
 	free(item->conf.key);
 	free(item->conf.command);
+	free(item->conf.cmd);
 	free(item->token);
 	free(item->value);
 	free(item);
@@ -216,18 +218,24 @@ static int check_if_different(struct trailer_item *in_tok,
 	return 1;
 }
 
-static char *apply_command(const char *command, const char *arg)
+static char *apply_command(struct conf_info *conf, const char *arg)
 {
 	struct strbuf cmd = STRBUF_INIT;
 	struct strbuf buf = STRBUF_INIT;
 	struct child_process cp = CHILD_PROCESS_INIT;
 	char *result;
 
-	strbuf_addstr(&cmd, command);
-	if (arg)
-		strbuf_replace(&cmd, TRAILER_ARG_STRING, arg);
-
-	strvec_push(&cp.args, cmd.buf);
+	if (conf->cmd) {
+		strbuf_addstr(&cmd, conf->cmd);
+		strvec_push(&cp.args, cmd.buf);
+		if (arg)
+			strvec_push(&cp.args, arg);
+	} else if (conf->command) {
+		strbuf_addstr(&cmd, conf->command);
+		if (arg)
+			strbuf_replace(&cmd, TRAILER_ARG_STRING, arg);
+		strvec_push(&cp.args, cmd.buf);
+	}
 	cp.env = local_repo_env;
 	cp.no_stdin = 1;
 	cp.use_shell = 1;
@@ -247,7 +255,7 @@ static char *apply_command(const char *command, const char *arg)
 
 static void apply_item_command(struct trailer_item *in_tok, struct arg_item *arg_tok)
 {
-	if (arg_tok->conf.command) {
+	if (arg_tok->conf.command || arg_tok->conf.cmd) {
 		const char *arg;
 		if (arg_tok->value && arg_tok->value[0]) {
 			arg = arg_tok->value;
@@ -257,7 +265,7 @@ static void apply_item_command(struct trailer_item *in_tok, struct arg_item *arg
 			else
 				arg = xstrdup("");
 		}
-		arg_tok->value = apply_command(arg_tok->conf.command, arg);
+		arg_tok->value = apply_command(&arg_tok->conf, arg);
 		free((char *)arg);
 	}
 }
@@ -430,6 +438,7 @@ static void duplicate_conf(struct conf_info *dst, const struct conf_info *src)
 	dst->name = xstrdup_or_null(src->name);
 	dst->key = xstrdup_or_null(src->key);
 	dst->command = xstrdup_or_null(src->command);
+	dst->cmd = xstrdup_or_null(src->cmd);
 }
 
 static struct arg_item *get_conf_item(const char *name)
@@ -454,8 +463,8 @@ static struct arg_item *get_conf_item(const char *name)
 	return item;
 }
 
-enum trailer_info_type { TRAILER_KEY, TRAILER_COMMAND, TRAILER_WHERE,
-			 TRAILER_IF_EXISTS, TRAILER_IF_MISSING };
+enum trailer_info_type { TRAILER_KEY, TRAILER_COMMAND, TRAILER_CMD,
+			TRAILER_WHERE, TRAILER_IF_EXISTS, TRAILER_IF_MISSING };
 
 static struct {
 	const char *name;
@@ -463,6 +472,7 @@ static struct {
 } trailer_config_items[] = {
 	{ "key", TRAILER_KEY },
 	{ "command", TRAILER_COMMAND },
+	{ "cmd", TRAILER_CMD },
 	{ "where", TRAILER_WHERE },
 	{ "ifexists", TRAILER_IF_EXISTS },
 	{ "ifmissing", TRAILER_IF_MISSING }
@@ -542,6 +552,11 @@ static int git_trailer_config(const char *conf_key, const char *value, void *cb)
 			warning(_("more than one %s"), conf_key);
 		conf->command = xstrdup(value);
 		break;
+	case TRAILER_CMD:
+		if (conf->cmd)
+			warning(_("more than one %s"), conf_key);
+		conf->cmd = xstrdup(value);
+		break;
 	case TRAILER_WHERE:
 		if (trailer_set_where(&conf->where, value))
 			warning(_("unknown value '%s' for key '%s'"), value, conf_key);