Condition Config: add minimum-version() and file-exists().

So: `@if minimum-version("6.2.4")` and `@if file-exists("filename")`.

doc/RELEASE-NOTES.md

@@ -12,6 +12,11 @@ This is work in progress and may not always be a stable version.
   * New `@if module-exists("modulename")` to check if a module exists on
     disk. You can use this with a subsequent `loadmodule` and config items,
     this can be handy with 3rd party modules.
+  * New `@if minimum-version("6.2.4")` to check if the UnrealIRCd version
+    is at least the specified version.
+  * New `@if file-exists("filename")` to check if a file exists.
+    Paths are relative to the conf directory, or absolute if starting
+    with `/`.
 
 ### Changes:
 * [GeoIP](https://www.unrealircd.org/docs/GeoIP):

include/h.h

@@ -1106,6 +1106,7 @@ extern MODVAR Client *remote_rehash_client;
 extern MODVAR json_t *json_rehash_log;
 extern MODVAR int debugfd;
 extern void convert_to_absolute_path(char **path, const char *reldir);
+extern char *convert_to_absolute_path_duplicate(char *path, char *reldir);
 extern int has_user_mode(Client *acptr, char mode);
 extern int has_channel_mode(Channel *channel, char mode);
 extern int has_channel_mode_raw(Cmode_t m, char mode);

include/struct.h

@@ -1649,7 +1649,7 @@ struct AuthConfig {
  * conf2 stuff -stskeeps
 */
 
-typedef enum ConfigIfCondition { IF_DEFINED=1, IF_VALUE=2, IF_MODULE_LOADED=3, IF_MODULE_EXISTS=4} ConfigIfCondition;
+typedef enum ConfigIfCondition { IF_DEFINED=1, IF_VALUE=2, IF_MODULE_LOADED=3, IF_MODULE_EXISTS=4, IF_MINIMUM_VERSION=5, IF_FILE_EXISTS=6} ConfigIfCondition;
 
 struct ConditionalConfig
 {

src/conf_preprocessor.c

@@ -35,6 +35,10 @@ PreprocessorItem evaluate_preprocessor_if(char *statement, const char *filename,
 	 * !module-loaded("something")
 	 * module-exists("something")
 	 * !module-exists("something")
+	 * minimum-version("6.2.0")
+	 * !minimum-version("6.2.0")
+	 * file-exists("something")
+	 * !file-exists("something")
 	 * defined($XYZ)
 	 * !defined($XYZ)
 	 * We do not support && or || or anything else at this time.
@@ -110,6 +114,66 @@ PreprocessorItem evaluate_preprocessor_if(char *statement, const char *filename,
 		*cc_out = cc;
 		return PREPROCESSOR_IF;
 	} else
+	if (!strncmp(p, "minimum-version", 15))
+	{
+		p += 15;
+		skip_whitespace(&p);
+		if (*p != '(')
+		{
+			config_error("%s:%i: expected '(' for minimum-version(...",
+				filename, linenumber);
+			return PREPROCESSOR_ERROR;
+		}
+		p++;
+		skip_whitespace(&p);
+		if (*p == '"')
+			p++;
+		name = p;
+		read_until(&p, ")\"");
+		if (!*p)
+		{
+			config_error("%s:%i: invalid if statement (termination error): %s",
+				filename, linenumber, statement);
+			return PREPROCESSOR_ERROR;
+		}
+		*p = '\0';
+		cc = safe_alloc(sizeof(ConditionalConfig));
+		cc->condition = IF_MINIMUM_VERSION;
+		cc->negative = negative;
+		safe_strdup(cc->name, name);
+		*cc_out = cc;
+		return PREPROCESSOR_IF;
+	} else
+	if (!strncmp(p, "file-exists", 11))
+	{
+		p += 11;
+		skip_whitespace(&p);
+		if (*p != '(')
+		{
+			config_error("%s:%i: expected '(' for file-exists(...",
+				filename, linenumber);
+			return PREPROCESSOR_ERROR;
+		}
+		p++;
+		skip_whitespace(&p);
+		if (*p == '"')
+			p++;
+		name = p;
+		read_until(&p, ")\"");
+		if (!*p)
+		{
+			config_error("%s:%i: invalid if statement (termination error): %s",
+				filename, linenumber, statement);
+			return PREPROCESSOR_ERROR;
+		}
+		*p = '\0';
+		cc = safe_alloc(sizeof(ConditionalConfig));
+		cc->condition = IF_FILE_EXISTS;
+		cc->negative = negative;
+		safe_strdup(cc->name, name);
+		*cc_out = cc;
+		return PREPROCESSOR_IF;
+	} else
 	if (!strncmp(p, "defined", 7))
 	{
 		p += 7;
@@ -392,6 +456,18 @@ int preprocessor_resolve_if(ConditionalConfig *cc, PreprocessorPhase phase)
 			if (file_exists(fullpath))
 				result = 1;
 		} else
+		if (cc->condition == IF_MINIMUM_VERSION)
+		{
+			if (strnatcasecmp(VERSIONONLY, cc->name) >= 0)
+				result = 1;
+		} else
+		if (cc->condition == IF_FILE_EXISTS)
+		{
+			char *fullpath = convert_to_absolute_path_duplicate(cc->name, CONFDIR);
+			if (file_exists(fullpath))
+				result = 1;
+			safe_free(fullpath);
+		} else
 		if (cc->condition == IF_DEFINED)
 		{
 			NameValuePrioList *d = find_config_define(cc->name);