submodule foreach: skip eval for more than one argument

'eval "$@"' creates an extra layer of shell interpretation, which is probably not expected by a user who passes multiple arguments to git submodule foreach: $ git grep "'" [searches for single quotes] $ git submodule foreach git grep "'" Entering '[submodule]' /usr/lib/git-core/git-submodule: 1: eval: Syntax error: Unterminated quoted string Stopping at '[submodule]'; script returned non-zero status. To fix this, if the user passes more than one argument, execute "$@" directly instead of passing it to eval. Examples: * Typical usage when adding an extra level of quoting is to pass a single argument representing the entire command to be passed to the shell. This doesn't change that. * One can imagine someone feeding untrusted input as an argument: git submodule foreach git grep "$variable" That currently results in a nonobvious shell code injection vulnerability. Executing the command named by the arguments directly, as in this patch, fixes it. Signed-off-by: Anders Kaseorg <andersk@mit.edu> Acked-by: Johan Herland <johan@herland.net> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>