Hi,
I noticed that GitWeb caches based on the "Last-Modified" header. Won't this break if somebody force pushes a branch with the new newest commit being older than the previous? The modification date will be older, which makes little sense to HTTP clients, and it would probably break since they use the "If-Modified-Since" header.
Wouldn't it make more sense to use the commit ID as an ETag? This would avoid this bug. Two different archive types would get the same ETag even if the HTTP content body is not equal, but I think this is not in violation of the HTTP standard, since caching is based on URL's AND ETags.
Here's a link to git_snapshot which is the relevant function: http://git.kernel.org/cgit/git/git.git/tree/gitweb/gitweb.perl#n7314
Looking forward to your feedback.
Regards, Janus