[PATCH v5 1/2] [GSOC] run-command: add shell_no_implicit_args option

["ZheNing Hu via GitGitGadget" <gitgitgadget@gmail.com>]

From: ZheNing Hu <adlternative@gmail.com>

When we use subprocess to run a shell-script, if we have any
args, git will add extra $@ to the end of the shell-script,
This can pass positional parameters correctly, But if we just
want to use some of these passed parameters, git will still
add an extra "$@", which contains all positional parameters we
passed. This does not meet our expectations.

E.g. our shell-script is:
"echo \"\$1\""
and pass $1 "abc", git will change our script to:
"echo \"\$1\" \"$@\""

The positional parameters we entered will be printed
repeatedly. So let add a new `shell_no_implicit_args`
to `struct child_process`, which can suppress the
joining of $@ if `shell_no_implicit_args` is set to 1,
this will allow us to use only few of positional args
in multi-parameter shell script, instead of using all
of them.

Signed-off-by: ZheNing Hu <adlternative@gmail.com>
---
 run-command.c | 8 ++++----
 run-command.h | 1 +
 trailer.c     | 1 +
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/run-command.c b/run-command.c
index be6bc128cd9d..a2cf6177f522 100644
--- a/run-command.c
+++ b/run-command.c
@@ -264,7 +264,7 @@ int sane_execvp(const char *file, char * const argv[])
 	return -1;
 }
 
-static const char **prepare_shell_cmd(struct strvec *out, const char **argv)
+static const char **prepare_shell_cmd(struct strvec *out, const char **argv, int shell_no_implicit_args)
 {
 	if (!argv[0])
 		BUG("shell command is empty");
@@ -281,7 +281,7 @@ static const char **prepare_shell_cmd(struct strvec *out, const char **argv)
 		 * If we have no extra arguments, we do not even need to
 		 * bother with the "$@" magic.
 		 */
-		if (!argv[1])
+		if (!argv[1] || shell_no_implicit_args)
 			strvec_push(out, argv[0]);
 		else
 			strvec_pushf(out, "%s \"$@\"", argv[0]);
@@ -416,7 +416,7 @@ static int prepare_cmd(struct strvec *out, const struct child_process *cmd)
 	if (cmd->git_cmd) {
 		prepare_git_cmd(out, cmd->argv);
 	} else if (cmd->use_shell) {
-		prepare_shell_cmd(out, cmd->argv);
+		prepare_shell_cmd(out, cmd->argv, cmd->shell_no_implicit_args);
 	} else {
 		strvec_pushv(out, cmd->argv);
 	}
@@ -929,7 +929,7 @@ int start_command(struct child_process *cmd)
 	if (cmd->git_cmd)
 		cmd->argv = prepare_git_cmd(&nargv, cmd->argv);
 	else if (cmd->use_shell)
-		cmd->argv = prepare_shell_cmd(&nargv, cmd->argv);
+		cmd->argv = prepare_shell_cmd(&nargv, cmd->argv, cmd->shell_no_implicit_args);
 
 	cmd->pid = mingw_spawnvpe(cmd->argv[0], cmd->argv, (char**) cmd->env,
 			cmd->dir, fhin, fhout, fherr);
diff --git a/run-command.h b/run-command.h
index d08414a92e73..9597c987c5bb 100644
--- a/run-command.h
+++ b/run-command.h
@@ -133,6 +133,7 @@ struct child_process {
 	 * argv[1], etc, do not need to be shell-quoted.
 	 */
 	unsigned use_shell:1;
+	unsigned shell_no_implicit_args:1;
 
 	unsigned stdout_to_stderr:1;
 	unsigned clean_on_exit:1;
diff --git a/trailer.c b/trailer.c
index be4e9726421c..35dd0f4c8512 100644
--- a/trailer.c
+++ b/trailer.c
@@ -231,6 +231,7 @@ static char *apply_command(const char *command, const char *arg)
 	cp.env = local_repo_env;
 	cp.no_stdin = 1;
 	cp.use_shell = 1;
+	cp.shell_no_implicit_args = 1;
 
 	if (capture_command(&cp, &buf, 1024)) {
 		error(_("running trailer command '%s' failed"), cmd.buf);
-- 
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