minor problems in git.c

[Robert Watson <robert.oo.watson@gmail.com>]

Hi,

There are some minor problems in git.c:

(1) potential buffer overrun.

        strncat(&git_command[len], "/git-", sizeof(git_command) - len);
        len += 5;
        strncat(&git_command[len], argv[i], sizeof(git_command) - len);

The first line will write one byte ('\0') beyond the end of
git_command, when sizeof(git_command) - len == 5.

The second line increase len by 5, without regarding how many bytes
are written in the first line.  It is possible to make len greater
than sizeof(git_command), therefore make the third argument of the
third line underflow, allowing almost any number of bytes from argv[1]
to be copied.

(2) environ

int main(int argc, char **argv, char **envp)
{
  ...
  execve(git_command, &argv[i], envp);
  ...
}

I am wondering whether the global variable "environ" could change when
you do setenv.  Would it be clear by using the "environ" as the third
argument of evecve()?

(3) printf("Failed to run command '%s': %s\n", git_command, strerror(errno));
should go to stderr?

Regards,
Robertoo