readme: Accept multiple candidates and test them.

The readme variable may now contain multiple space deliminated entries,
which per usual are either a filepath or a git ref filepath. If multiple
are specified, cgit will now select the first one in the list that
exists. This is to make it easier to specify multiple default readme
types in the main cgitrc file and have them automatically get applied to
each repo based on what exists.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

ui-summary.c

@@ -95,70 +95,71 @@ void cgit_print_summary()
 	html("</table>");
 }
 
-void cgit_print_repo_readme(char *path)
+/* The caller must free filename and ref after calling this. */
+void cgit_parse_readme(const char *readme, const char *path, char **filename, char **ref, struct cgit_repo *repo)
 {
-	char *slash, *tmp, *colon, *ref;
-	int free_filename = 0;
+	const char *slash, *colon;
 
-	if (!ctx.repo->readme || !(*ctx.repo->readme))
+	*filename = NULL;
+	*ref = NULL;
+
+	if (!readme || !(*readme))
 		return;
 
-	ref = NULL;
-
 	/* Check if the readme is tracked in the git repo. */
-	colon = strchr(ctx.repo->readme, ':');
+	colon = strchr(readme, ':');
 	if (colon && strlen(colon) > 1) {
-		*colon = '\0';
 		/* If it starts with a colon, we want to use
 		 * the default branch */
-		if (colon == ctx.repo->readme && ctx.repo->defbranch)
-			ref = ctx.repo->defbranch;
+		if (colon == readme && repo->defbranch)
+			*ref = xstrdup(repo->defbranch);
 		else
-			ref = ctx.repo->readme;
-		ctx.repo->readme = colon + 1;
-		if (!(*ctx.repo->readme))
-			return;
+			*ref = xstrndup(readme, colon - readme);
+		readme = colon + 1;
 	}
 
 	/* Prepend repo path to relative readme path unless tracked. */
-	if (!ref && *ctx.repo->readme != '/')
-		ctx.repo->readme = fmtalloc("%s/%s", ctx.repo->path,
-						ctx.repo->readme);
+	if (!(*ref) && *readme != '/')
+		readme = fmtalloc("%s/%s", repo->path, readme);
 
 	/* If a subpath is specified for the about page, make it relative
-	 * to the directory containing the configured readme.
-	 */
+	 * to the directory containing the configured readme. */
 	if (path) {
-		slash = strrchr(ctx.repo->readme, '/');
+		slash = strrchr(readme, '/');
 		if (!slash) {
 			if (!colon)
 				return;
 			slash = colon;
 		}
-		free_filename = 1;
-		tmp = xmalloc(slash - ctx.repo->readme + 1 + strlen(path) + 1);
-		strncpy(tmp, ctx.repo->readme, slash - ctx.repo->readme + 1);
-		strcpy(tmp + (slash - ctx.repo->readme + 1), path);
+		*filename = xmalloc(slash - readme + 1 + strlen(path) + 1);
+		strncpy(*filename, readme, slash - readme + 1);
+		strcpy(*filename + (slash - readme + 1), path);
 	} else
-		tmp = ctx.repo->readme;
+		*filename = xstrdup(readme);
+}
+
+void cgit_print_repo_readme(char *path)
+{
+	char *filename, *ref;
+	cgit_parse_readme(ctx.repo->readme, path, &filename, &ref, ctx.repo);
 
 	/* Print the calculated readme, either from the git repo or from the
 	 * filesystem, while applying the about-filter.
 	 */
 	html("<div id='summary'>");
 	if (ctx.repo->about_filter) {
-		ctx.repo->about_filter->argv[1] = tmp;
+		ctx.repo->about_filter->argv[1] = filename;
 		cgit_open_filter(ctx.repo->about_filter);
 	}
 	if (ref)
-		cgit_print_file(tmp, ref);
+		cgit_print_file(filename, ref);
 	else
-		html_include(tmp);
+		html_include(filename);
 	if (ctx.repo->about_filter) {
 		cgit_close_filter(ctx.repo->about_filter);
 		ctx.repo->about_filter->argv[1] = NULL;
 	}
 	html("</div>");
-	if (free_filename)
-		free(tmp);
+	free(filename);
+	free(ref);
 }