Implement include command

The include command (`include <path>`) makes it possible to include sub
config files from the main config file (or from within other sub config
files).

The include command uses the following rules for including config files:

* the `path` can be either a full path or a path that is relative to the
  parent config. Shell expansion is supported, so it's possible to do
  `include ~/.config/sway.d/*`.
* The same config file can only be included once (to prevent include
  cycles). If a config is included multiple times it will just be
  ignored after it has been included once.
* Including a sub config file is the same as inserting the content of
  that file into the parent config, thus rules about overwriting
  bindsyms etc. works the same as for a single config.

Implement #542

sway/config.c

@@ -2,6 +2,7 @@
 #include <stdbool.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <libgen.h>
 #include <wordexp.h>
 #include <sys/types.h>
 #include <sys/wait.h>
@@ -126,6 +127,7 @@ void free_config(struct sway_config *config) {
 	list_free(config->output_configs);
 
 	list_free(config->active_bar_modifiers);
+	free_flat_list(config->config_chain);
 	free(config->font);
 	free(config);
 }
@@ -175,6 +177,9 @@ static void config_defaults(struct sway_config *config) {
 	config->gaps_outer = 0;
 
 	config->active_bar_modifiers = create_list();
+
+	config->config_chain = create_list();
+	config->current_config = NULL;
 }
 
 static int compare_modifiers(const void *left, const void *right) {
@@ -237,16 +242,7 @@ static char *get_config_path(void) {
 	return NULL; // Not reached
 }
 
-bool load_config(const char *file) {
-	input_init();
-
-	char *path;
-	if (file != NULL) {
-		path = strdup(file);
-	} else {
-		path = get_config_path();
-	}
-
+static bool load_config(const char *path, struct sway_config *config) {
 	sway_log(L_INFO, "Loading config from %s", path);
 
 	if (path == NULL) {
@@ -257,20 +253,12 @@ bool load_config(const char *file) {
 	FILE *f = fopen(path, "r");
 	if (!f) {
 		sway_log(L_ERROR, "Unable to open %s for reading", path);
-		free(path);
 		return false;
 	}
-	free(path);
 
-	bool config_load_success;
-	if (config) {
-		config_load_success = read_config(f, true);
-	} else {
-		config_load_success = read_config(f, false);
-	}
+	bool config_load_success = read_config(f, config);
 	fclose(f);
 
-	update_active_bar_modifiers();
 
 	if (!config_load_success) {
 		sway_log(L_ERROR, "Error(s) loading config!");
@@ -279,17 +267,129 @@ bool load_config(const char *file) {
 	return true;
 }
 
-bool read_config(FILE *file, bool is_active) {
+bool load_main_config(const char *file, bool is_active) {
+	input_init();
+
+	char *path;
+	if (file != NULL) {
+		path = strdup(file);
+	} else {
+		path = get_config_path();
+	}
+
 	struct sway_config *old_config = config;
 	config = calloc(1, sizeof(struct sway_config));
 
 	config_defaults(config);
-	config->reading = true;
 	if (is_active) {
 		sway_log(L_DEBUG, "Performing configuration file reload");
 		config->reloading = true;
 		config->active = true;
 	}
+
+	config->current_config = path;
+	list_add(config->config_chain, path);
+
+	config->reading = true;
+	bool success = load_config(path, config);
+
+	if (is_active) {
+		config->reloading = false;
+	}
+
+	if (old_config) {
+		free_config(old_config);
+	}
+	config->reading = false;
+
+	if (success) {
+		update_active_bar_modifiers();
+	}
+
+	return success;
+}
+
+static bool load_include_config(const char *path, const char *parent_dir, struct sway_config *config) {
+	// save parent config
+	const char *parent_config = config->current_config;
+
+	char *full_path = strdup(path);
+	int len = strlen(path);
+	if (len >= 1 && path[0] != '/') {
+		len = len + strlen(parent_dir) + 2;
+		full_path = malloc(len * sizeof(char));
+		snprintf(full_path, len, "%s/%s", parent_dir, path);
+	}
+
+	char *real_path = realpath(full_path, NULL);
+	free(full_path);
+
+	// check if config has already been included
+	int j;
+	for (j = 0; j < config->config_chain->length; ++j) {
+		char *old_path = config->config_chain->items[j];
+		if (strcmp(real_path, old_path) == 0) {
+			sway_log(L_DEBUG, "%s already included once, won't be included again.", real_path);
+			free(real_path);
+			return false;
+		}
+	}
+
+	config->current_config = real_path;
+	list_add(config->config_chain, real_path);
+	int index = config->config_chain->length - 1;
+
+	if (!load_config(real_path, config)) {
+		free(real_path);
+		config->current_config = parent_config;
+		list_del(config->config_chain, index);
+		return false;
+	}
+
+	// restore current_config
+	config->current_config = parent_config;
+	return true;
+}
+
+bool load_include_configs(const char *path, struct sway_config *config) {
+	char *wd = getcwd(NULL, 0);
+	char *parent_path = strdup(config->current_config);
+	const char *parent_dir = dirname(parent_path);
+
+	if (chdir(parent_dir) < 0) {
+		free(parent_path);
+		free(wd);
+		return false;
+	}
+
+	wordexp_t p;
+
+	if (wordexp(path, &p, 0) < 0) {
+		free(parent_path);
+		free(wd);
+		return false;
+	}
+
+	char **w = p.we_wordv;
+	size_t i;
+	for (i = 0; i < p.we_wordc; ++i) {
+		load_include_config(w[i], parent_dir, config);
+	}
+	free(parent_path);
+	wordfree(&p);
+
+	// restore wd
+	if (chdir(wd) < 0) {
+		free(wd);
+		sway_log(L_ERROR, "failed to restore working directory");
+		return false;
+	}
+
+	free(wd);
+	return true;
+}
+
+bool read_config(FILE *file, struct sway_config *config) {
 	bool success = true;
 	enum cmd_status block = CMD_BLOCK_END;
 
@@ -386,15 +486,6 @@ bool read_config(FILE *file, bool is_active) {
 		free(res);
 	}
 
-	if (is_active) {
-		config->reloading = false;
-		arrange_windows(&root_container, -1, -1);
-	}
-	if (old_config) {
-		free_config(old_config);
-	}
-
-	config->reading = false;
 	return success;
 }