1 file changed, 110 insertions, 18 deletions
diff --git a/source/ui-shared.c b/source/ui-shared.c
index db441e0..066c25d 100644
--- a/source/ui-shared.c
+++ b/source/ui-shared.c
@@ -373,15 +373,48 @@ static void add_clone_urls(void (*fn)(const char *), char *urls, char *suffix)
 	strbuf_list_free(url_list);
 }
 
-static int print_branch_option(const struct reference *ref, void *counter)
+/*
+ * The id parameter pins a page to one commit while the rest of the chrome
+ * keeps naming the branch. Answer that commit, or null when the request
+ * follows the branch or the pin lands on its tip anyway.
+ */
+static const struct object_id *pinned_oid(void)
+{
+	static struct object_id oid;
+	struct object_id head_oid;
+	struct commit *commit;
+
+	if (!ctx.repo || !ctx.qry.has_oid || !ctx.qry.oid || !ctx.qry.head)
+		return NULL;
+	if (repo_get_oid(the_repository, ctx.qry.oid, &oid) ||
+	    repo_get_oid(the_repository, ctx.qry.head, &head_oid))
+		return NULL;
+	// A full hex id resolves without being looked up, so only peeling to a
+	// commit proves the pin names history, and a tag pinned to the tip
+	// compares equal only by its peeled commit.
+	commit = lookup_commit_reference_gently(the_repository, &oid, 1);
+	if (!commit)
+		return NULL;
+	oidcpy(&oid, &commit->object.oid);
+	if (oideq(&oid, &head_oid))
+		return NULL;
+	return &oid;
+}
+
+struct branch_option_data {
+	int count;
+	const char *selected;
+};
+
+static int print_branch_option(const struct reference *ref, void *data)
 {
-	int *count = counter;
+	struct branch_option_data *opt = data;
 	const char *name = ref->name;
 	// The switcher runs on every page, so it is bounded like the refs list.
-	if (ctx.cfg.max_ref_count && *count >= ctx.cfg.max_ref_count)
+	if (ctx.cfg.max_ref_count && opt->count >= ctx.cfg.max_ref_count)
 		return -1;
-	(*count)++;
-	html_option(name, name, ctx.qry.head);
+	opt->count++;
+	html_option(name, name, opt->selected);
 	return 0;
 }
 
@@ -422,15 +455,33 @@ static void print_header(void)
 	// A repository with no commits has no branches to list, so the
 	// switcher would be an empty select next to a switch button.
 	if (ctx.repo && ctx.env.authenticated && !ctx.empty_repo) {
+		const struct object_id *pinned = pinned_oid();
+		// Only one option may carry selected, and a pinned commit
+		// outranks the branch it was reached from.
+		struct branch_option_data opt = {
+			.selected = pinned ? NULL : ctx.qry.head,
+		};
+		char *oid = ctx.qry.oid, *oid2 = ctx.qry.oid2;
+
 		html("<form class='branch-switch' method='get'>\n");
+		// Switching branch means leaving the pinned commit behind, so
+		// the id fields stay out of the form.
+		ctx.qry.oid = ctx.qry.oid2 = NULL;
 		cgit_add_hidden_formfields(0, 1, ctx.qry.page);
+		ctx.qry.oid = oid;
+		ctx.qry.oid2 = oid2;
 		html("<select name='h' aria-label='Branch' data-autosubmit='1'>\n");
-		int branch_count = 0;
+		if (pinned) {
+			const char *hex = oid_to_hex(pinned);
+
+			html_option(hex, cgit_fmt("%.*s (detached)",
+						  SHORT_HASH_LEN, hex), hex);
+		}
 		refs_for_each_branch_ref(get_main_ref_store(the_repository),
-					 print_branch_option, &branch_count);
+					 print_branch_option, &opt);
 		if (ctx.repo->enable_remote_branches)
 			refs_for_each_remote_ref(get_main_ref_store(the_repository),
-						 print_branch_option, &branch_count);
+						 print_branch_option, &opt);
 		html("</select> ");
 		html("<input type='submit' value='switch'>");
 		html("</form>\n");
@@ -1134,6 +1185,7 @@ void cgit_redirect(const char *url, bool permanent)
 
 void cgit_print_docstart(void)
 {
+	const struct object_id *pinned;
 	char *host = cgit_hosturl();
 
 	if (ctx.cfg.embedded) {
@@ -1154,6 +1206,10 @@ void cgit_print_docstart(void)
 	// An error page reached before a title was chosen still has to name
 	// itself, since an empty title element is not valid.
 	html_txt(ctx.page.title ? ctx.page.title : ctx.cfg.root_title);
+	// The auth page goes out before the repository is opened, when
+	// pinned_oid cannot resolve anything yet.
+	if (ctx.env.authenticated && (pinned = pinned_oid()))
+		html_txtf(" @ %.*s", SHORT_HASH_LEN, oid_to_hex(pinned));
 	html("</title>\n");
 	htmlf("<meta name='generator' content='cgit %s'>\n", cgit_version);
 	if (ctx.cfg.robots && *ctx.cfg.robots) {
@@ -1298,6 +1354,8 @@ void cgit_add_hidden_formfields(int incl_head, int incl_search,
 
 void cgit_print_pageheader(void)
 {
+	const struct object_id *pinned;
+
 	html("<div id='cgit'>\n");
 	if (!ctx.env.authenticated || !ctx.cfg.noheader)
 		print_header();
@@ -1320,17 +1378,51 @@ void cgit_print_pageheader(void)
 	}
 	if (ctx.env.authenticated)
 		html("</nav>\n");
-	if (ctx.env.authenticated && ctx.repo && ctx.qry.vpath) {
-		html("<nav class='path' aria-label='breadcrumb'>");
-		html("path: ");
-		print_path_crumbs(ctx.qry.vpath);
-		if (ctx.repo->enable_follow_links && !strcmp(ctx.qry.page, "log")) {
+	pinned = ctx.env.authenticated && ctx.repo ? pinned_oid() : NULL;
+	// The commit and diff pages name the commit they show as their own
+	// content, so the rev crumb would only repeat them.
+	if (pinned && ctx.qry.page && (!strcmp(ctx.qry.page, "commit") ||
+				       !strcmp(ctx.qry.page, "diff")))
+		pinned = NULL;
+	if ((ctx.env.authenticated && ctx.repo && ctx.qry.vpath) || pinned) {
+		html("<nav class='path' aria-label='");
+		html(ctx.qry.vpath ? "breadcrumb" : "revision");
+		html("'>");
+		if (ctx.qry.vpath) {
+			// The nav lays out as a flex row, which would make
+			// every crumb its own item and swallow the spaces
+			// between them, so the run stays inline in a span.
+			html("<span>path: ");
+			print_path_crumbs(ctx.qry.vpath);
+			if (ctx.repo->enable_follow_links &&
+			    !strcmp(ctx.qry.page, "log")) {
+				html(" (");
+				ctx.qry.follow = !ctx.qry.follow;
+				self_link(ctx.qry.follow ? "follow" : "unfollow",
+					  NULL, NULL);
+				ctx.qry.follow = !ctx.qry.follow;
+				html(")");
+			}
+			html("</span>");
+		}
+		if (pinned) {
+			const char *hex = oid_to_hex(pinned);
+			char *oid = ctx.qry.oid;
+
+			html("<span class='rev'>rev: ");
+			cgit_commit_link(cgit_fmt("%.*s", SHORT_HASH_LEN, hex),
+					 NULL, NULL, ctx.qry.head, hex,
+					 ctx.qry.vpath);
 			html(" (");
-			ctx.qry.follow = !ctx.qry.follow;
-			self_link(ctx.qry.follow ? "follow" : "unfollow",
-				  NULL, NULL);
-			ctx.qry.follow = !ctx.qry.follow;
-			html(")");
+			// self_link reads the pin out of ctx.qry, so lifting
+			// it is what makes the link land back on the tip of
+			// the branch.
+			ctx.qry.oid = NULL;
+			ctx.qry.has_oid = 0;
+			self_link("latest", NULL, NULL);
+			ctx.qry.oid = oid;
+			ctx.qry.has_oid = 1;
+			html(")</span>");
 		}
 		html("</nav>\n");
 	}