Allow use of regular expressions for coloring

When defining colors, strings of the form "/.../" will be interpreted as
regular expressions.

E.g. color "/([^:]+):([0-9]+):(|([0-9]+):)[ \t]+(note|warning|error): (.*)(\[-W([a-zA-Z0-8_-]+)\]|)/"	yellow	default	bold

Closes #1249

Suggested-by: Sebastian Gniazdowski <[email protected]>

doc/tigrc.5.adoc

@@ -978,6 +978,8 @@ color diff-chunk	magenta	default
 color "Reported-by:"	green	default
 # View-specific color
 color tree.date		black	cyan	bold
+# Custom color
+color "/(note|warning|error):/"	yellow	default	bold
 --------------------------------------------------------------------------
 
 Or in the Git configuration files:
@@ -998,7 +1000,8 @@ Area names::
 
 	Can be either a built-in area name or a custom quoted string. The
 	latter allows custom color rules to be added for lines matching a
-	quoted string.
+	quoted string. Strings of the form "/.../" are interpreted as
+	regular expressions.
 	Valid built-in area names are described below. Note, all names are
 	case-insensitive, and you may use '-', and '_' interchangeably,
 	e.g. "Diff-Header" and "DIFF_HEADER" are the same.

include/tig/line.h

@@ -115,6 +115,7 @@ struct line_rule {
 	int namelen;		/* Size of option name. */
 	const char *line;	/* The start of line to match. */
 	int linelen;		/* Size of string to match. */
+	regex_t *regex;		/* Pre-compiled regexp. */
 	struct line_info info;	/* List of line info matching this rule. */
 };
 

src/line.c

@@ -35,6 +35,9 @@ get_line_type(const char *line)
 	for (type = 0; type < line_rules; type++) {
 		struct line_rule *rule = &line_rule[type];
 
+		if (rule->regex && !regexec(rule->regex, line, 0, NULL, 0))
+			return type;
+
 		/* Case insensitive search matches Signed-off-by lines better. */
 		if (rule->linelen && linelen >= rule->linelen &&
 		    !strncasecmp(rule->line, line, rule->linelen))
@@ -89,7 +92,7 @@ get_line_info(const char *prefix, enum line_type type)
 }
 
 static struct line_info *
-init_line_info(const char *prefix, const char *name, size_t namelen, const char *line, size_t linelen)
+init_line_info(const char *prefix, const char *name, size_t namelen, const char *line, size_t linelen, regex_t *regex)
 {
 	struct line_rule *rule;
 
@@ -101,6 +104,7 @@ init_line_info(const char *prefix, const char *name, size_t namelen, const char
 	rule->namelen = namelen;
 	rule->line = line;
 	rule->linelen = linelen;
+	rule->regex = regex;
 
 	rule->info.prefix = prefix;
 	rule->info.fg = COLOR_DEFAULT;
@@ -110,7 +114,7 @@ init_line_info(const char *prefix, const char *name, size_t namelen, const char
 }
 
 #define INIT_BUILTIN_LINE_INFO(type, line) \
-	init_line_info(NULL, #type, STRING_SIZE(#type), (line), STRING_SIZE(line))
+	init_line_info(NULL, #type, STRING_SIZE(#type), (line), STRING_SIZE(line), NULL)
 
 static struct line_rule *
 find_line_rule(struct line_rule *query)
@@ -145,11 +149,15 @@ add_line_rule(const char *prefix, struct line_rule *query)
 		if (query->name)
 			return NULL;
 
-		/* Quoted line. */
-		query->line = strndup(query->line, query->linelen);
-		if (!query->line)
-			return NULL;
-		return init_line_info(prefix, "", 0, query->line, query->linelen);
+		return init_line_info(prefix, "", 0, query->line, query->linelen, query->regex);
+	}
+
+	/* When a rule already exists and we are just adding view-specific
+	 * colors, query->line and query->regex can be freed. */
+	free((void *) query->line);
+	if (query->regex) {
+		regfree(query->regex);
+		free(query->regex);
 	}
 
 	for (info = &rule->info; info; last = info, info = info->next)

src/options.c

@@ -373,9 +373,46 @@ parse_color_name(const char *color, struct line_rule *rule, const char **prefix_
 
 	memset(rule, 0, sizeof(*rule));
 	if (is_quoted(*color)) {
-		rule->line = color + 1;
-		rule->linelen = strlen(color) - 2;
+		/* Interpret strings of the form "/.../" as regular expressions. */
+		if (strlen(color) >= 4 && color[1] == '/' && color[strlen(color) - 2] == '/') {
+			int regex_err;
+
+			/* rule->line and rule->regex are allocated here rather
+			 * than in add_line_rule() to allow proper error reporting.
+			 * Though only rule->regex will be used for matching regular
+			 * expressions, rule->line and rule->linelen are still filled
+			 * to look up exiting rules when defining view-specific
+			 * colors. */
+			rule->linelen = strlen(color) - 4;
+			rule->line = strndup(color + 2, rule->linelen);
+			if (!rule->line)
+				return ERROR_OUT_OF_MEMORY;
+
+			rule->regex = calloc(1, sizeof(*rule->regex));
+			if (!rule->regex) {
+				free((void *) rule->line);
+				return ERROR_OUT_OF_MEMORY;
+			}
+
+			regex_err = regcomp(rule->regex, rule->line, REG_EXTENDED);
+
+			if (regex_err != 0) {
+				char buf[SIZEOF_STR];
+				regerror(regex_err, rule->regex, buf, sizeof(buf));
+				free((void *) rule->line);
+				free(rule->regex);
+				return error("Invalid color mapping: %s", buf);
+			}
+		} else {
+			rule->linelen = strlen(color) - 2;
+			rule->line = strndup(color + 1, rule->linelen);
+			if (!rule->line)
+				return ERROR_OUT_OF_MEMORY;
+		}
 	} else {
+		/* Built-in area names are preloaded on first call to
+		 * find_line_rule(), so rule->name is only used to look
+		 * up an existing rule and does not need to persist. */
 		rule->name = color;
 		rule->namelen = strlen(color);
 	}