[PATCH v2 1/3] config --global --edit: create a template file if needed

@@ -445,6 +445,20 @@ static int get_urlmatch(const char *var, const char *url)
 	return 0;
 }
 
+static char *default_user_config(void)
+{
+	struct strbuf buf = STRBUF_INIT;
+	strbuf_addf(&buf,
+		    _("# This is Git's user configuration file.\n"
+		      "[core]\n"
+		      "# Please adapt and uncomment the following lines:\n"
+		      "#	user = %s\n"
+		      "#	email = %s\n"),
+		    ident_default_name(),
+		    ident_default_email());
+	return strbuf_detach(&buf, NULL);
+}
+
 int cmd_config(int argc, const char **argv, const char *prefix)
 {
 	int nongit = !startup_info->have_repository;

@@ -551,6 +565,8 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 		}
 	}
 	else if (actions == ACTION_EDIT) {
+		const char *config_file = given_config_source.file ?
+			given_config_source.file : git_path("config");
 		check_argc(argc, 0, 0);
 		if (!given_config_source.file && nongit)
 			die("not in a git directory");

@@ -559,9 +575,18 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 		if (given_config_source.blob)
 			die("editing blobs is not supported");
 		git_config(git_default_config, NULL);
-		launch_editor(given_config_source.file ?
-			      given_config_source.file : git_path("config"),
-			      NULL, NULL);
+		if (use_global_config) {
+			int fd = open(config_file, O_CREAT | O_EXCL | O_WRONLY, 0666);
+			if (fd) {
+				char *content = default_user_config();
+				write_str_in_full(fd, content);
+				free(content);
+				close(fd);
+			}
+			else if (errno != EEXIST)
+				die_errno(_("cannot create configuration file %s"), config_file);
+		}
+		launch_editor(config_file, NULL, NULL);
 	}
 	else if (actions == ACTION_SET) {
 		int ret;

@@ -1061,6 +1061,7 @@ extern const char *git_author_info(int);
 extern const char *git_committer_info(int);
 extern const char *fmt_ident(const char *name, const char *email, const char *date_str, int);
 extern const char *fmt_name(const char *name, const char *email);
+extern const char *ident_default_name(void);
 extern const char *ident_default_email(void);
 extern const char *git_editor(void);
 extern const char *git_pager(int stdout_is_tty);

@@ -102,7 +102,7 @@ static void copy_email(const struct passwd *pw, struct strbuf *email)
 	add_domainname(email);
 }
 
-static const char *ident_default_name(void)
+const char *ident_default_name(void)
 {
 	if (!git_default_name.len) {
 		copy_gecos(xgetpwuid_self(), &git_default_name);

@@ -42,7 +42,20 @@ static const char * const builtin_status_usage[] = {
 	NULL
 };
 
-static const char implicit_ident_advice[] =
+static const char implicit_ident_advice_noconfig[] =
+N_("Your name and email address were configured automatically based\n"
+"on your username and hostname. Please check that they are accurate.\n"
+"You can suppress this message by setting them explicitly. Run the\n"
+"following command and follow the instructions in your editor to edit\n"
+"your configuration file:\n"
+"\n"
+"    git config --global --edit\n"
+"\n"
+"After doing this, you may fix the identity used for this commit with:\n"
+"\n"
+"    git commit --amend --reset-author\n");
+
+static const char implicit_ident_advice_config[] =
 N_("Your name and email address were configured automatically based\n"
 "on your username and hostname. Please check that they are accurate.\n"
 "You can suppress this message by setting them explicitly:\n"

@@ -1402,6 +1415,23 @@ int cmd_status(int argc, const char **argv, const char *prefix)
 	return 0;
 }
 
+static const char *implicit_ident_advice() {
+	char *user_config = NULL;
+	char *xdg_config = NULL;
+	int config_exists;
+
+	home_config_paths(&user_config, &xdg_config, "config");
+	config_exists = file_exists(user_config) || file_exists(xdg_config);
+	free(user_config);
+	free(xdg_config);
+
+	if (config_exists)
+		return _(implicit_ident_advice_config);
+	else
+		return _(implicit_ident_advice_noconfig);
+
+}
+
 static void print_summary(const char *prefix, const unsigned char *sha1,
 			  int initial_commit)
 {

@@ -1440,7 +1470,7 @@ static void print_summary(const char *prefix, const unsigned char *sha1,
 		strbuf_addbuf_percentquote(&format, &committer_ident);
 		if (advice_implicit_identity) {
 			strbuf_addch(&format, '\n');
-			strbuf_addstr(&format, _(implicit_ident_advice));
+			strbuf_addstr(&format, implicit_ident_advice());
 		}
 	}
 	strbuf_release(&author_ident);

@@ -148,10 +148,12 @@ void home_config_paths(char **global, char **xdg, char *file)
 			*global = mkpathdup("%s/.gitconfig", home);
 	}
 
-	if (!xdg_home)
-		*xdg = NULL;
-	else
-		*xdg = mkpathdup("%s/git/%s", xdg_home, file);
+	if (xdg) {
+		if (!xdg_home)
+			*xdg = NULL;
+		else
+			*xdg = mkpathdup("%s/git/%s", xdg_home, file);
+	}
 
 	free(to_free);
 }