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;
 }
 

ui-blob.c

@@ -13,7 +13,7 @@
 #include "ui-shared.h"
 
 struct walk_tree_context {
-	char *match_path;
+	const char *match_path;
 	unsigned char *matched_sha1;
 	int found_path;
 };
@@ -31,6 +31,32 @@ static int walk_tree(const unsigned char *sha1, const char *base, int baselen,
 	return 0;
 }
 
+int cgit_ref_path_exists(const char *path, const char *ref)
+{
+        unsigned char sha1[20];
+        unsigned long size;
+        struct pathspec_item path_items = {
+                .match = path,
+                .len = strlen(path)
+        };
+        struct pathspec paths = {
+                .nr = 1,
+                .items = &path_items
+        };
+        struct walk_tree_context walk_tree_ctx = {
+                .match_path = path,
+                .matched_sha1 = sha1,
+                .found_path = 0
+        };
+
+        if (get_sha1(ref, sha1))
+                return 0;
+        if (sha1_object_info(sha1, &size) != OBJ_COMMIT) 
+                return 0;
+        read_tree_recursive(lookup_commit_reference(sha1)->tree, "", 0, 0, &paths, walk_tree, &walk_tree_ctx);
+        return walk_tree_ctx.found_path;
+}
+
 int cgit_print_file(char *path, const char *head)
 {
 	unsigned char sha1[20];

ui-blob.h

@@ -1,6 +1,7 @@
 #ifndef UI_BLOB_H
 #define UI_BLOB_H
 
+extern int cgit_ref_path_exists(const char *path, const char *ref);
 extern int cgit_print_file(char *path, const char *head);
 extern void cgit_print_blob(const char *hex, char *path, const char *head);
 

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);
 }

ui-summary.h

@@ -1,6 +1,7 @@
 #ifndef UI_SUMMARY_H
 #define UI_SUMMARY_H
 
+extern void cgit_parse_readme(const char *readme, const char *path, char **filename, char **ref, struct cgit_repo *repo);
 extern void cgit_print_summary();
 extern void cgit_print_repo_readme(char *path);