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>

cgit.c

@@ -14,6 +14,8 @@
 #include "html.h"
 #include "ui-shared.h"
 #include "ui-stats.h"
+#include "ui-blob.h"
+#include "ui-summary.h"
 #include "scan-tree.h"
 
 const char *cgit_version = CGIT_VERSION;
@@ -469,6 +471,38 @@ static char *guess_defbranch(void)
 	return xstrdup(ref + 11);
 }
 
+static void choose_readme(struct cgit_repo *repo)
+{
+	char *entry, *filename, *ref;
+
+	/* If there's no space, we skip the possibly expensive
+	 * selection process. */
+	if (!repo->readme || !strchr(repo->readme, ' '))
+		return;
+
+	for (entry = strtok(repo->readme, " "); entry; entry = strtok(NULL, " ")) {
+		cgit_parse_readme(entry, NULL, &filename, &ref, repo);
+		if (!(*filename)) {
+			free(filename);
+			free(ref);
+			continue;
+		}
+		if (*ref && cgit_ref_path_exists(filename, ref)) {
+			free(filename);
+			free(ref);
+			break;
+		}
+		if (!access(filename, R_OK)) {
+			free(filename);
+			free(ref);
+			break;
+		}
+		free(filename);
+		free(ref);
+	}
+	repo->readme = entry;
+}
+
 static int prepare_repo_cmd(struct cgit_context *ctx)
 {
 	unsigned char sha1[20];
@@ -537,6 +571,7 @@ static int prepare_repo_cmd(struct cgit_context *ctx)
 	}
 	sort_string_list(&ctx->repo->submodules);
 	cgit_prepare_repo_env(ctx->repo);
+	choose_readme(ctx->repo);
 	return 0;
 }