run_command: teach API users to use embedded 'args' more

The child_process structure has an embedded strvec for formulating
the command line argument list these days, but code that predates
the wide use of it prepared a separate char *argv[] array and
manually set the child_process.argv pointer point at it.

Teach these old-style code to lose the separate argv[] array.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

convert.c

@@ -638,7 +638,6 @@ static int filter_buffer_or_fd(int in, int out, void *data)
 	struct child_process child_process = CHILD_PROCESS_INIT;
 	struct filter_params *params = (struct filter_params *)data;
 	int write_err, status;
-	const char *argv[] = { NULL, NULL };
 
 	/* apply % substitution to cmd */
 	struct strbuf cmd = STRBUF_INIT;
@@ -656,9 +655,7 @@ static int filter_buffer_or_fd(int in, int out, void *data)
 	strbuf_expand(&cmd, params->cmd, strbuf_expand_dict_cb, &dict);
 	strbuf_release(&path);
 
-	argv[0] = cmd.buf;
-
-	child_process.argv = argv;
+	strvec_push(&child_process.args, cmd.buf);
 	child_process.use_shell = 1;
 	child_process.in = -1;
 	child_process.out = out;

credential.c

@@ -274,11 +274,9 @@ static int run_credential_helper(struct credential *c,
 				 int want_output)
 {
 	struct child_process helper = CHILD_PROCESS_INIT;
-	const char *argv[] = { NULL, NULL };
 	FILE *fp;
 
-	argv[0] = cmd;
-	helper.argv = argv;
+	strvec_push(&helper.args, cmd);
 	helper.use_shell = 1;
 	helper.in = -1;
 	if (want_output)

submodule.c

@@ -1726,14 +1726,6 @@ unsigned is_submodule_modified(const char *path, int ignore_untracked)
 int submodule_uses_gitfile(const char *path)
 {
 	struct child_process cp = CHILD_PROCESS_INIT;
-	const char *argv[] = {
-		"submodule",
-		"foreach",
-		"--quiet",
-		"--recursive",
-		"test -f .git",
-		NULL,
-	};
 	struct strbuf buf = STRBUF_INIT;
 	const char *git_dir;
 
@@ -1746,7 +1738,10 @@ int submodule_uses_gitfile(const char *path)
 	strbuf_release(&buf);
 
 	/* Now test that all nested submodules use a gitfile too */
-	cp.argv = argv;
+	strvec_pushl(&cp.args,
+		     "submodule", "foreach", "--quiet",	"--recursive",
+		     "test -f .git", NULL);
+
 	prepare_submodule_repo_env(&cp.env_array);
 	cp.git_cmd = 1;
 	cp.no_stdin = 1;

trailer.c

@@ -221,15 +221,13 @@ static char *apply_command(const char *command, const char *arg)
 	struct strbuf cmd = STRBUF_INIT;
 	struct strbuf buf = STRBUF_INIT;
 	struct child_process cp = CHILD_PROCESS_INIT;
-	const char *argv[] = {NULL, NULL};
 	char *result;
 
 	strbuf_addstr(&cmd, command);
 	if (arg)
 		strbuf_replace(&cmd, TRAILER_ARG_STRING, arg);
 
-	argv[0] = cmd.buf;
-	cp.argv = argv;
+	strvec_push(&cp.args, cmd.buf);
 	cp.env = local_repo_env;
 	cp.no_stdin = 1;
 	cp.use_shell = 1;