[PATCH 5/6] config: factor out set_config_source_file()

[Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx>]

In the next patch, "config" is taught to move some config variables
from one file to another. We need to specify two locations, source and
destination, and the plan is reusing the same --global/--local/...
option. Factor this code out for reuse later.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx>
---
 builtin/config.c | 113 +++++++++++++++++++++++++----------------------
 1 file changed, 59 insertions(+), 54 deletions(-)

diff --git a/builtin/config.c b/builtin/config.c
index c22d25de12..61a6a5a0e1 100644
--- a/builtin/config.c
+++ b/builtin/config.c
@@ -71,6 +71,64 @@ static int show_origin;
 
 static NORETURN void usage_builtin_config(void);
 
+static void set_config_source_file(void)
+{
+	int nongit = !startup_info->have_repository;
+
+	if (use_global_config + use_system_config + use_local_config +
+	    use_worktree_config +
+	    !!given_config_source.file + !!given_config_source.blob > 1)
+		die(_("only one config file at a time"));
+
+	if (use_local_config && nongit)
+		die(_("--local can only be used inside a git repository"));
+
+	if (given_config_source.blob && nongit)
+		die(_("--blob can only be used inside a git repository"));
+
+	if (given_config_source.file &&
+			!strcmp(given_config_source.file, "-")) {
+		given_config_source.file = NULL;
+		given_config_source.use_stdin = 1;
+	}
+
+	if (use_global_config) {
+		char *user_config = expand_user_path("~/.gitconfig", 0);
+		char *xdg_config = xdg_config_home("config");
+
+		if (!user_config)
+			/*
+			 * It is unknown if HOME/.gitconfig exists, so
+			 * we do not know if we should write to XDG
+			 * location; error out even if XDG_CONFIG_HOME
+			 * is set and points at a sane location.
+			 */
+			die(_("$HOME not set"));
+
+		if (access_or_warn(user_config, R_OK, 0) &&
+		    xdg_config && !access_or_warn(xdg_config, R_OK, 0)) {
+			given_config_source.file = xdg_config;
+			free(user_config);
+		} else {
+			given_config_source.file = user_config;
+			free(xdg_config);
+		}
+	}
+	else if (use_system_config)
+		given_config_source.file = git_etc_gitconfig();
+	else if (use_local_config)
+		given_config_source.file = git_pathdup("config");
+	else if (use_worktree_config) {
+		given_config_source.file = get_worktree_config(the_repository);
+		if (!given_config_source.file)
+			die(_("--worktree cannot be used with multiple "
+			      "working trees unless the config\n"
+			      "extension worktreeConfig is enabled. "
+			      "Please read \"CONFIGURATION FILE\"\n"
+			      "section in \"git help worktree\" for details"));
+	}
+}
+
 static int option_parse_type(const struct option *opt, const char *arg,
 			     int unset)
 {
@@ -604,60 +662,7 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 			     builtin_config_usage,
 			     PARSE_OPT_STOP_AT_NON_OPTION);
 
-	if (use_global_config + use_system_config + use_local_config +
-	    use_worktree_config +
-	    !!given_config_source.file + !!given_config_source.blob > 1) {
-		error(_("only one config file at a time"));
-		usage_builtin_config();
-	}
-
-	if (use_local_config && nongit)
-		die(_("--local can only be used inside a git repository"));
-
-	if (given_config_source.blob && nongit)
-		die(_("--blob can only be used inside a git repository"));
-
-	if (given_config_source.file &&
-			!strcmp(given_config_source.file, "-")) {
-		given_config_source.file = NULL;
-		given_config_source.use_stdin = 1;
-	}
-
-	if (use_global_config) {
-		char *user_config = expand_user_path("~/.gitconfig", 0);
-		char *xdg_config = xdg_config_home("config");
-
-		if (!user_config)
-			/*
-			 * It is unknown if HOME/.gitconfig exists, so
-			 * we do not know if we should write to XDG
-			 * location; error out even if XDG_CONFIG_HOME
-			 * is set and points at a sane location.
-			 */
-			die(_("$HOME not set"));
-
-		if (access_or_warn(user_config, R_OK, 0) &&
-		    xdg_config && !access_or_warn(xdg_config, R_OK, 0)) {
-			given_config_source.file = xdg_config;
-			free(user_config);
-		} else {
-			given_config_source.file = user_config;
-			free(xdg_config);
-		}
-	}
-	else if (use_system_config)
-		given_config_source.file = git_etc_gitconfig();
-	else if (use_local_config)
-		given_config_source.file = git_pathdup("config");
-	else if (use_worktree_config) {
-		given_config_source.file = get_worktree_config(the_repository);
-		if (!given_config_source.file)
-			die(_("--worktree cannot be used with multiple "
-			      "working trees unless the config\n"
-			      "extension worktreeConfig is enabled. "
-			      "Please read \"CONFIGURATION FILE\"\n"
-			      "section in \"git help worktree\" for details"));
-	}
+	set_config_source_file();
 
 	if (respect_includes_opt == -1)
 		config_options.respect_includes = !given_config_source.file;
-- 
2.20.0.482.g66447595a7