Git LFS pointers permit extension entries before the `version` header line about git-lfs HOT 1 OPEN

As an addendum to this report, we also permit non-alphanumeric characters after the ext-<n>-<name> key values because our regular expression isn't terminated with a \z. For example:

$ cat <<EOF | git lfs pointer --check --stdin && echo ok
version https://git-lfs.github.com/spec/v1
ext-0-foo:()[] sha256:b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c
oid sha256:0123456789012345678901234567890123456789012345678901234567890123
size 4
EOF
ok

So while [a-zA-Z0-9_] are parsed as the "name" of the extension entry, miscellaneous non-whitespace characters are then allowed after that. This is also something we can fix in a major release, and again possibly something where we may want to also bump the pointer version.

from git-lfs.