[WIP PATCH 03/26] Save setup_git_dir* info globally for later use

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

For one thing, this could help catching setup_git_dir being run twice,
which is usually wrong.

This also helps moving up setup_git_dir* from inside builtin commands
to handle_internal_command(). Without this, run_builtin()
needs to find another way to pass "nongit_ok" to builtin commands.

The main program has to intialize startup_info pointer properly. For
builtin commands, git.c will take care of that. If startup_info is
NULL, the prior behavior should apply.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Could have save the command name in startup_info too, so error
 messages are clearer..

 cache.h       |    8 ++++++++
 environment.c |    1 +
 git.c         |   31 +++++++++++++++++++++++--------
 setup.c       |   14 +++++++++++++-
 4 files changed, 45 insertions(+), 9 deletions(-)

diff --git a/cache.h b/cache.h
index d478eff..fcbed37 100644
--- a/cache.h
+++ b/cache.h
@@ -1040,4 +1040,12 @@ void overlay_tree_on_cache(const char *tree_name, const char *prefix);
 char *alias_lookup(const char *alias);
 int split_cmdline(char *cmdline, const char ***argv);
 
+/* git.c */
+struct startup_info {
+	const char *prefix;
+	int have_set_gitdir;
+	int have_repository;
+};
+extern struct startup_info *startup_info;
+
 #endif /* CACHE_H */
diff --git a/environment.c b/environment.c
index 739ec27..1ab8815 100644
--- a/environment.c
+++ b/environment.c
@@ -52,6 +52,7 @@ enum object_creation_mode object_creation_mode = OBJECT_CREATION_MODE;
 char *notes_ref_name;
 int grafts_replace_parents = 1;
 int core_apply_sparse_checkout;
+struct startup_info *startup_info;
 
 /* Parallel index stat data preload? */
 int core_preload_index = 0;
diff --git a/git.c b/git.c
index b3e23f1..ea29cca 100644
--- a/git.c
+++ b/git.c
@@ -13,6 +13,8 @@ const char git_usage_string[] =
 const char git_more_info_string[] =
 	"See 'git help COMMAND' for more information on a specific command.";
 
+static struct startup_info opts;
+struct startup_info *startup_info;
 static int use_pager = -1;
 struct pager_config {
 	const char *cmd;
@@ -206,9 +208,6 @@ static int handle_alias(int *argcp, const char ***argv)
 		ret = 1;
 	}
 
-	if (subdir && chdir(subdir))
-		die_errno("Cannot change to '%s'", subdir);
-
 	errno = saved_errno;
 
 	return ret;
@@ -234,13 +233,26 @@ static int run_builtin(struct cmd_struct *p, int argc, const char **argv)
 {
 	int status, help;
 	struct stat st;
-	const char *prefix;
 
-	prefix = NULL;
 	help = argc == 2 && !strcmp(argv[1], "-h");
 	if (!help) {
-		if (p->option & RUN_SETUP)
-			prefix = setup_git_directory();
+		/* handle_alias() may have set up gitdir for alias lookup */
+		if (startup_info->have_set_gitdir) {
+			if (p->option & RUN_SETUP) {
+				if (!startup_info->have_repository)
+					die("No repository found");
+			}
+			else {
+				/* This is WRONG, but we can't get rid of it now */
+				startup_info->have_set_gitdir = 0;
+				if (startup_info->prefix && chdir(startup_info->prefix))
+					die("Cannot change to '%s'", startup_info->prefix);
+			}
+		}
+		else {
+			if (p->option & RUN_SETUP)
+				setup_git_directory();
+		}
 
 		if (use_pager == -1 && p->option & RUN_SETUP)
 			use_pager = check_pager_config(p->cmd);
@@ -254,7 +266,7 @@ static int run_builtin(struct cmd_struct *p, int argc, const char **argv)
 
 	trace_argv_printf(argv, "trace: built-in: git");
 
-	status = p->fn(argc, argv, prefix);
+	status = p->fn(argc, argv, startup_info->prefix);
 	if (status)
 		return status;
 
@@ -473,6 +485,9 @@ int main(int argc, const char **argv)
 {
 	const char *cmd;
 
+	startup_info = &opts;
+	memset(startup_info, 0, sizeof(*startup_info));
+
 	cmd = git_extract_argv0_path(argv[0]);
 	if (!cmd)
 		cmd = "git-help";
diff --git a/setup.c b/setup.c
index 183bcf6..0c05d36 100644
--- a/setup.c
+++ b/setup.c
@@ -236,7 +236,13 @@ void setup_work_tree(void)
 		git_dir = make_absolute_path(git_dir);
 	if (!work_tree || chdir(work_tree))
 		die("This operation must be run in a work tree");
+
+	/* we know gitdir is already set, we only adjust it to relative path */
+	if (startup_info)
+		startup_info->have_set_gitdir = 0;
 	set_git_dir(make_relative_path(git_dir, work_tree));
+	if (startup_info)
+		startup_info->have_set_gitdir = 1;
 	initialized = 1;
 }
 
@@ -447,8 +453,14 @@ const char *setup_git_directory_gently(int *nongit_ok)
 	const char *prefix;
 
 	prefix = setup_git_directory_gently_1(nongit_ok);
-	if (!nongit_ok || (!*nongit_ok && check_repository_format_gently(nongit_ok)))
+	if (startup_info)
+		startup_info->have_set_gitdir = 1;
+	if ((!nongit_ok || !*nongit_ok) && check_repository_format_gently(nongit_ok))
 		prefix = NULL;
+	if (startup_info) {
+		startup_info->prefix = prefix;
+		startup_info->have_repository = !nongit_ok || !*nongit_ok;
+	}
 	return prefix;
 }
 
-- 
1.7.0.195.g637a2