snapshot: support tar signature for compressed tar

This adds support for kernel.org style signatures where the uncompressed
tar archive is signed and compressed later. The signature is valid for
all tar* snapshots.

We have a filter which snapshots may be generated and downloaded. This has
to allow tar signatures now even if tar itself is not allowed. To simplify
things we allow all signatures.

Signed-off-by: Christian Hesse <mail@eworm.de>

ui-shared.c

@@ -1114,7 +1114,7 @@ void cgit_compose_snapshot_prefix(struct strbuf *filename, const char *base,
 void cgit_print_snapshot_links(const struct cgit_repo *repo, const char *ref,
 			       const char *separator)
 {
-	const struct cgit_snapshot_format* f;
+	const struct cgit_snapshot_format *f;
 	struct strbuf filename = STRBUF_INIT;
 	const char *basename;
 	size_t prefixlen;
@@ -1139,6 +1139,13 @@ void cgit_print_snapshot_links(const struct cgit_repo *repo, const char *ref,
 			cgit_snapshot_link("sig", NULL, NULL, NULL, NULL,
 					   filename.buf);
 			html(")");
+		} else if (starts_with(f->suffix, ".tar") && cgit_snapshot_get_sig(ref, &cgit_snapshot_formats[0])) {
+			strbuf_setlen(&filename, strlen(filename.buf) - strlen(f->suffix));
+			strbuf_addstr(&filename, ".tar.asc");
+			html(" (");
+			cgit_snapshot_link("sig", NULL, NULL, NULL, NULL,
+					   filename.buf);
+			html(")");
 		}
 		html(separator);
 	}

ui-snapshot.c

@@ -86,6 +86,7 @@ static int write_tar_xz_archive(const char *hex, const char *prefix)
 }
 
 const struct cgit_snapshot_format cgit_snapshot_formats[] = {
+	/* .tar must remain the 0 index */
 	{ ".tar",	"application/x-tar",	write_tar_archive	},
 	{ ".tar.gz",	"application/x-gzip",	write_tar_gzip_archive	},
 	{ ".tar.bz2",	"application/x-bzip2",	write_tar_bzip2_archive	},
@@ -268,7 +269,7 @@ void cgit_print_snapshot(const char *head, const char *hex,
 	}
 
 	f = get_format(filename);
-	if (!f || !(ctx.repo->snapshots & cgit_snapshot_format_bit(f))) {
+	if (!f || (!sig_filename && !(ctx.repo->snapshots & cgit_snapshot_format_bit(f)))) {
 		cgit_print_error_page(400, "Bad request",
 				"Unsupported snapshot format: %s", filename);
 		return;