remote rename/remove: gently handle remote.pushDefault config

When renaming a remote with

    git remote rename X Y
    git remote remove X

Git already renames or removes any branch.<name>.remote and
branch.<name>.pushRemote configurations if their value is X.

However remote.pushDefault needs a more gentle approach, as this may be
set in a non-repo configuration file. In such a case only a warning is
printed, such as:

warning: The global configuration remote.pushDefault in:
	$HOME/.gitconfig:35
now names the non-existent remote origin

It is changed to remote.pushDefault = Y or removed when set in a repo
configuration though.

Signed-off-by: Bert Wesarg <bert.wesarg@googlemail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/remote.c b/builtin/remote.c
index a2379a1..555d4c8 100644
--- a/builtin/remote.c
+++ b/builtin/remote.c
@@ -615,6 +615,56 @@ static int migrate_file(struct remote *remote)
 	return 0;
 }
 
+struct push_default_info
+{
+	const char *old_name;
+	enum config_scope scope;
+	struct strbuf origin;
+	int linenr;
+};
+
+static int config_read_push_default(const char *key, const char *value,
+	void *cb)
+{
+	struct push_default_info* info = cb;
+	if (strcmp(key, "remote.pushdefault") ||
+	    !value || strcmp(value, info->old_name))
+		return 0;
+
+	info->scope = current_config_scope();
+	strbuf_reset(&info->origin);
+	strbuf_addstr(&info->origin, current_config_name());
+	info->linenr = current_config_line();
+
+	return 0;
+}
+
+static void handle_push_default(const char* old_name, const char* new_name)
+{
+	struct push_default_info push_default = {
+		old_name, CONFIG_SCOPE_UNKNOWN, STRBUF_INIT, -1 };
+	git_config(config_read_push_default, &push_default);
+	if (push_default.scope >= CONFIG_SCOPE_COMMAND)
+		; /* pass */
+	else if (push_default.scope >= CONFIG_SCOPE_LOCAL) {
+		int result = git_config_set_gently("remote.pushDefault",
+						   new_name);
+		if (new_name && result && result != CONFIG_NOTHING_SET)
+			die(_("could not set '%s'"), "remote.pushDefault");
+		else if (!new_name && result && result != CONFIG_NOTHING_SET)
+			die(_("could not unset '%s'"), "remote.pushDefault");
+	} else if (push_default.scope >= CONFIG_SCOPE_SYSTEM) {
+		/* warn */
+		warning(_("The %s configuration remote.pushDefault in:\n"
+			  "\t%s:%d\n"
+			  "now names the non-existent remote '%s'"),
+			config_scope_name(push_default.scope),
+			push_default.origin.buf, push_default.linenr,
+			old_name);
+	}
+}
+
+
 static int mv(int argc, const char **argv)
 {
 	struct option options[] = {
@@ -750,6 +800,9 @@ static int mv(int argc, const char **argv)
 			die(_("creating '%s' failed"), buf.buf);
 	}
 	string_list_clear(&remote_branches, 1);
+
+	handle_push_default(rename.old_name, rename.new_name);
+
 	return 0;
 }
 
@@ -835,6 +888,8 @@ static int rm(int argc, const char **argv)
 		strbuf_addf(&buf, "remote.%s", remote->name);
 		if (git_config_rename_section(buf.buf, NULL) < 1)
 			return error(_("Could not remove config section '%s'"), buf.buf);
+
+		handle_push_default(remote->name, NULL);
 	}
 
 	return result;