[PATCH] Do not use SHELL_PATH from build system in prepare_shell_cmd on Windows

[Johannes Sixt <j.sixt@viscovery.net>]

From: Johannes Sixt <j6t@kdbg.org>

The recent change to use SHELL_PATH instead of "sh" to spawn shell commands
is not suited for Windows:

- The default setting, "/bin/sh", does not work when git has to run the
  shell because it is a POSIX style path, but not a proper Windows style
  path.

- If it worked, it would hard-code a position in the files system where
  the shell is expected, making git (more precisely, the POSIX toolset that
  is needed alongside git) non-relocatable. But we cannot sacrifice
  relocatability on Windows.

- Apart from that, even though the Makefile leaves SHELL_PATH set to
  "/bin/sh" for the Windows builds, the build system passes a mangled path
  to the compiler, and something like "D:/Src/msysgit/bin/sh" is used,
  which is doubly bad because it points to where /bin/sh resolves to on
  the system where git was built.

- Finally, the system's CreateProcess() function that is used under
  mingw.c's hood does not work with forward slashes and cannot find the
  shell.

Undo the earlier change on Windows.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
---
Am 3/31/2012 3:33, schrieb Ben Walton:
> +#ifndef SHELL_PATH
> +# define SHELL_PATH "/bin/sh"
> +#endif
> +
>  struct child_to_clean {
>  	pid_t pid;
>  	struct child_to_clean *next;
> @@ -90,7 +94,7 @@ static const char **prepare_shell_cmd(const char **argv)
>  		die("BUG: shell command is empty");
>  
>  	if (strcspn(argv[0], "|&;<>()$`\\\"' \t\n*?[#~=%") != strlen(argv[0])) {
> -		nargv[nargc++] = "sh";
> +		nargv[nargc++] = SHELL_PATH;
>  		nargv[nargc++] = "-c";
>  
>  		if (argc < 2)

This looked so obviously correct, that I carelessly did not test the
change. But given that the first two points addressed in the commit
message above are actually dealbreakers, I should have noticed this issue
much earlier.

-- Hannes

 run-command.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/run-command.c b/run-command.c
index 2af3e0f..e4edede 100644
--- a/run-command.c
+++ b/run-command.c
@@ -94,7 +94,11 @@ static const char **prepare_shell_cmd(const char **argv)
 		die("BUG: shell command is empty");
 
 	if (strcspn(argv[0], "|&;<>()$`\\\"' \t\n*?[#~=%") != strlen(argv[0])) {
+#ifndef WIN32
 		nargv[nargc++] = SHELL_PATH;
+#else
+		nargv[nargc++] = "sh";
+#endif
 		nargv[nargc++] = "-c";
 
 		if (argc < 2)
-- 
1.7.10.1370.ga6f62.dirty