Bundle downloads run `git bundle create` into a temp file under
`data/tmp/git-repo-content` and copy it to the response, so every
download puts a second, repo-sized copy on disk before the first byte is
sent. If the process dies mid-request that copy is stranded: the startup
sweep only drops files older than 3 days, and cannot remove a directory
that still holds a newer file.
Streaming `git bundle create -` to the response removes that copy.
`CreateArchive` above already uses the same gitcmd pattern, and the
bundle bytes are unchanged (existing integration assertions on the exact
length still pass).
One consequence: git can now fail after output starts, so a mid-stream
failure truncates the body instead of returning an error.
I did not act on the TODO. A temp ref only works under `refs/heads/*`;
with `refs/bundle/temp-*` the bundle carries no branch and clones empty,
so I noted that on the TODO.
Fixes https://github.com/go-gitea/gitea/issues/38447
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Co-authored-by: silverwind <me@silverwind.io>