pager: drop "wait for output to run less" hack

Commit 35ce862 (pager: Work around window resizing bug in
'less', 2007-01-24) causes git's pager sub-process to wait
to receive input after forking but before exec-ing the
pager. To handle this, run-command had to grow a "pre-exec
callback" feature. Unfortunately, this feature does not work
at all on Windows (where we do not fork), and interacts
poorly with run-command's parent notification system. Its
use should be discouraged.

The bug in less was fixed in version 406, which was released
in June 2007. It is probably safe at this point to remove
our workaround. That lets us rip out the preexec_cb feature
entirely.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

pager.c

@@ -11,21 +11,6 @@
  * something different on Windows.
  */
 
-#ifndef WIN32
-static void pager_preexec(void)
-{
-	/*
-	 * Work around bug in "less" by not starting it until we
-	 * have real input
-	 */
-	fd_set in;
-
-	FD_ZERO(&in);
-	FD_SET(0, &in);
-	select(1, &in, NULL, &in, NULL);
-}
-#endif
-
 static const char *pager_argv[] = { NULL, NULL };
 static struct child_process pager_process;
 
@@ -93,9 +78,6 @@ void setup_pager(void)
 		static const char *env[] = { "LESS=FRSX", NULL };
 		pager_process.env = env;
 	}
-#ifndef WIN32
-	pager_process.preexec_cb = pager_preexec;
-#endif
 	if (start_command(&pager_process))
 		return;
 

run-command.c

@@ -394,16 +394,6 @@ int start_command(struct child_process *cmd)
 					unsetenv(*cmd->env);
 			}
 		}
-		if (cmd->preexec_cb) {
-			/*
-			 * We cannot predict what the pre-exec callback does.
-			 * Forgo parent notification.
-			 */
-			close(child_notifier);
-			child_notifier = -1;
-
-			cmd->preexec_cb();
-		}
 		if (cmd->git_cmd) {
 			execv_git_cmd(cmd->argv);
 		} else if (cmd->use_shell) {

run-command.h

@@ -39,7 +39,6 @@ struct child_process {
 	unsigned stdout_to_stderr:1;
 	unsigned use_shell:1;
 	unsigned clean_on_exit:1;
-	void (*preexec_cb)(void);
 };
 
 int start_command(struct child_process *);