From: Johannes Schindelin <johannes.schindelin@gmx.de>

Git's own `git archive` inserts that header, but it often gets into the
way of `import-tars.perl` e.g. when a prefix was specified (for example
via `--prefix=my-project-1.0.0/`, or when downloading a `.tar.gz` from
GitHub releases): this prefix _should_ be stripped.

Let's just skip it.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Submitted-As: https://lore.kernel.org/git/pull.577.git.1584968924555.gitgitgadget@gmail.com