git wrapper: allow setup_git_directory_gently() be called earlier

In the spirit of v1.4.2-rc3~34^2^2 (Call setup_git_directory() much
earlier, 2006-07-28), let run_builtin() take care of searching for a
repository for built-ins that want to make use of one if present.

So now you can mark your command with RUN_SETUP_GENTLY and use

	nongit = !startup_info->have_repository;

in place of

	prefix = setup_git_directory_gently(&nongit);

and everything will be the same, except the repository is
discovered a little sooner.

As v1.7.2~16^2 (2010-07-14) explains, this should allow more commands
to robustly use features like "git --paginate" that look at local
configuration before the command is actually run.

This patch sets up the infrastructure.  Later patches will teach
particular commands to use it.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git.c

@@ -230,13 +230,14 @@ static int handle_alias(int *argcp, const char ***argv)
 
 const char git_version_string[] = GIT_VERSION;
 
-#define RUN_SETUP	(1<<0)
-#define USE_PAGER	(1<<1)
+#define RUN_SETUP		(1<<0)
+#define RUN_SETUP_GENTLY	(1<<1)
+#define USE_PAGER		(1<<2)
 /*
  * require working tree to be present -- anything uses this needs
  * RUN_SETUP for reading from the configuration file.
  */
-#define NEED_WORK_TREE	(1<<2)
+#define NEED_WORK_TREE		(1<<3)
 
 struct cmd_struct {
 	const char *cmd;
@@ -255,8 +256,12 @@ static int run_builtin(struct cmd_struct *p, int argc, const char **argv)
 	if (!help) {
 		if (p->option & RUN_SETUP)
 			prefix = setup_git_directory();
+		if (p->option & RUN_SETUP_GENTLY) {
+			int nongit_ok;
+			prefix = setup_git_directory_gently(&nongit_ok);
+		}
 
-		if (use_pager == -1 && p->option & RUN_SETUP)
+		if (use_pager == -1 && p->option & (RUN_SETUP | RUN_SETUP_GENTLY))
 			use_pager = check_pager_config(p->cmd);
 		if (use_pager == -1 && p->option & USE_PAGER)
 			use_pager = 1;