"git -p cmd" to page anywhere

This allows you to say:

	git -p diff v2.6.16-rc5..

and the command pipes the output of any git command to your pager.

[jc: this resurrects a month old RFC patch with improvement
 suggested by Linus to call it --paginate instead of --less.]

Signed-off-by: Junio C Hamano <junkio@cox.net>

pager.c

@@ -5,6 +5,8 @@
  * something different on Windows, for example.
  */
 
+int pager_in_use;
+
 static void run_pager(const char *pager)
 {
 	execlp(pager, pager, NULL);
@@ -24,6 +26,8 @@ void setup_pager(void)
 	else if (!*pager || !strcmp(pager, "cat"))
 		return;
 
+	pager_in_use = 1; /* means we are emitting to terminal */
+
 	if (pipe(fd) < 0)
 		return;
 	pid = fork();