[PATCH] Add run_command_v_opt_cd: chdir into a directory before exec

[Alex Riesen <raa.lkml@gmail.com>]

It can make code simplier (no need to preserve cwd) and safer
(no chance the cwd of the current process is accidentally forgotten).

Signed-off-by: Alex Riesen <raa.lkml@gmail.com>
---
Alex Riesen, Sat, May 19, 2007 00:00:14 +0200:
> skimo@liacs.nl, Fri, May 18, 2007 21:24:58 +0200:
> > +	if (!getcwd(cwd, sizeof(cwd)) || cwd[0] != '/')
> > +		die("Unable to read current working directory");
> > +
> > +	if (chdir(path))
> > +		die("Cannot move to '%s'", path);
> > +
> 
> How about modifying run_command to chdir after fork?
> 
> You'd save the hassle of save/restoring cwd and don't mess up process'
> context (which is always a good idea to preserve). The code'd be
> simplier, too.
> 

something like this

 run-command.c |   27 ++++++++++++++++++++++-----
 run-command.h |    2 ++
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/run-command.c b/run-command.c
index eff523e..043b570 100644
--- a/run-command.c
+++ b/run-command.c
@@ -73,6 +73,9 @@ int start_command(struct child_process *cmd)
 			close(cmd->out);
 		}
 
+		if (cmd->dir && chdir(cmd->dir))
+			die("exec %s: cd to %s failed (%s)", cmd->argv[0],
+			    cmd->dir, strerror(errno));
 		if (cmd->git_cmd) {
 			execv_git_cmd(cmd->argv);
 		} else {
@@ -133,13 +136,27 @@ int run_command(struct child_process *cmd)
 	return finish_command(cmd);
 }
 
+static void prepare_run_command_v_opt(struct child_process *cmd,
+				      const char **argv, int opt)
+{
+	memset(cmd, 0, sizeof(*cmd));
+	cmd->argv = argv;
+	cmd->no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
+	cmd->git_cmd = opt & RUN_GIT_CMD ? 1 : 0;
+	cmd->stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
+}
+
 int run_command_v_opt(const char **argv, int opt)
 {
 	struct child_process cmd;
-	memset(&cmd, 0, sizeof(cmd));
-	cmd.argv = argv;
-	cmd.no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
-	cmd.git_cmd = opt & RUN_GIT_CMD ? 1 : 0;
-	cmd.stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
+	prepare_run_command_v_opt(&cmd, argv, opt);
+	return run_command(&cmd);
+}
+
+int run_command_v_opt_cd(const char **argv, int opt, const char *dir)
+{
+	struct child_process cmd;
+	prepare_run_command_v_opt(&cmd, argv, opt);
+	cmd.dir = dir;
 	return run_command(&cmd);
 }
diff --git a/run-command.h b/run-command.h
index 3680ef9..cbd7484 100644
--- a/run-command.h
+++ b/run-command.h
@@ -16,6 +16,7 @@ struct child_process {
 	pid_t pid;
 	int in;
 	int out;
+	const char *dir;
 	unsigned close_in:1;
 	unsigned close_out:1;
 	unsigned no_stdin:1;
@@ -32,5 +33,6 @@ int run_command(struct child_process *);
 #define RUN_GIT_CMD	     2	/*If this is to be git sub-command */
 #define RUN_COMMAND_STDOUT_TO_STDERR 4
 int run_command_v_opt(const char **argv, int opt);
+int run_command_v_opt_cd(const char **argv, int opt, const char *dir);
 
 #endif
-- 
1.5.2.rc3.83.gbbb0