add support for snapshot tarballs

- reworked cgit_print_snapshot to use a list of supported archivers and pick
	one for the suffix supplied
- moved printing of snaphot links into ui-snapshot and make it iterate through
	the said list

ui-snapshot.c

@@ -8,40 +8,61 @@
 
 #include "cgit.h"
 
-static void cgit_print_zip(struct cacheitem *item, const char *hex, 
-			   const char *prefix, const char *filename)
-{
-	struct archiver_args args;
-	struct commit *commit;
-	unsigned char sha1[20];
-
-	if (get_sha1(hex, sha1)) {
-		cgit_print_error(fmt("Bad object id: %s", hex));
-		return;
-	}
-	commit = lookup_commit_reference(sha1);
-
-	if (!commit) {
-		cgit_print_error(fmt("Not a commit reference: %s", hex));
-		return;
-	}
-
-	memset(&args, 0, sizeof(args));
-	args.base = fmt("%s/", prefix);
-	args.tree = commit->tree;
-	
-	cgit_print_snapshot_start("application/x-zip", filename, item);
-	write_zip_archive(&args);
-}
-
+static const struct snapshot_archive_t {
+    	const char *suffix;
+	const char *mimetype;
+	write_archive_fn_t write_func;
+}	snapshot_archives[] = {
+	{ ".zip", "application/x-zip", write_zip_archive },
+	{ ".tar.gz", "application/x-gzip", write_tar_archive }
+};
 
 void cgit_print_snapshot(struct cacheitem *item, const char *hex, 
-			 const char *format, const char *prefix,
-			 const char *filename)
+			 const char *prefix, const char *filename)
 {
-	if (!strcmp(format, "zip"))
-		cgit_print_zip(item, hex, prefix, filename);
-	else
-		cgit_print_error(fmt("Unsupported snapshot format: %s", 
-				     format));
+	int fnl = strlen(filename);
+	int f;
+    	for(f=0;f<(sizeof(snapshot_archives)/sizeof(*snapshot_archives));++f) {
+		const struct snapshot_archive_t* sat = &snapshot_archives[f];
+		int sl = strlen(sat->suffix);
+		if(fnl<sl || strcmp(&filename[fnl-sl],sat->suffix))
+			continue;
+
+		struct archiver_args args;
+		struct commit *commit;
+		unsigned char sha1[20];
+
+		if(get_sha1(hex, sha1)) {
+			cgit_print_error(fmt("Bad object id: %s", hex));
+			return;
+		}
+		commit = lookup_commit_reference(sha1);
+
+		if(!commit) {
+			cgit_print_error(fmt("Not a commit reference: %s", hex));
+			return;;
+		}
+
+		memset(&args,0,sizeof(args));
+		args.base = fmt("%s/", prefix);
+		args.tree = commit->tree;
+
+		cgit_print_snapshot_start(sat->mimetype, filename, item);
+		(*sat->write_func)(&args);
+		return;
+	}
+	cgit_print_error(fmt("Unsupported snapshot format: %s", filename));
+}
+
+void cgit_print_snapshot_links(const char *repo,const char *hex)
+{
+    	char *filename;
+	int f;
+    	for(f=0;f<(sizeof(snapshot_archives)/sizeof(*snapshot_archives));++f) {
+		const struct snapshot_archive_t* sat = &snapshot_archives[f];
+		filename = fmt("%s-%s%s",repo,hex,sat->suffix);
+		htmlf("<a href='%s'>%s</a><br/>",
+			cgit_pageurl(repo,"snapshot",
+			    fmt("id=%s&amp;name=%s",hex,filename)), filename);
+	}
 }