git-interpret-trailers and period characters in the key

[Brendan Jackman <jackmanb@google.com>]

Hi folks,

Just debugging one of my scripts and I found that
git-interpret-trailers behaves surprisingly on trailer keys containing
'.' characters:

❯❯  cat commit.txt
my commit title

My-Footer: foo

❯❯  git interpret-trailers --parse commit.txt
My-Footer: foo

❯❯  cat commit2.txt
my commit title

My-Footer: foo
My-6.11-Version: bar

❯❯  git interpret-trailers --parse commit.txt

Basically, as soon as any trailer key contains a period (which in my
case, it does because the trailer keys refer to versions of of
software, i.e. "this commit was backported from the following Linux
kernel commit which appeared in version 6.1"), it stops parsing the
trailer block.

My guess is that this is just that it doesn't allow periods in the
trailer key, and once there's one line in the block that isn't a
trailer, it no longer meets the requirements described in the man
page.

I can't find anything in the man page about why the period character
should break this. Am I missing anything there?

Cheers,
Brendan

❯❯  git --version
git version 2.49.0.472.ge94155a9ec-goog

(IIUC that -goog in the version string is just noting that we have
monitoring logic added to our internal Git built to spot people
leaking IP, there's no actual feature customisation)