Comment by jolmg

I've changed my mind regarding the email format not being a problem. I was thinking of emailed git commits as this ad-hoc thing, but I forgot that `git-format-patch` and `git-am` exist. It's not just an incompatibility between them and `patch`. If you have a line `---` in your git commit message, `git-format-patch` will not somehow escape it, resulting in git-am truncating your git commit message. The email commit format is kinda bad. Github `.patch` exports are just being compatible with `git-am`, so I don't think it's a bug with them.

This is Re:

> I do not yet know whether the bug belongs to GNU patch, GitHub’s .patch export, or the broader patch-format contract.

I don't think this is a problem with GNU patch or the patch format per se, just the emailed commit format. I think the patch format's good because it allows it to be embedded in other texts and also allows comments or extended syntax between hunks. For example, the lines

  diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
  index 15ba592236e845..725a49a0eee72e 100644

not being part of the hunk and probably being seen as a comment by `patch`.

Simply changing `git-am` to accept commit messages being indented in the email format would allow Github fix the issue of their .patch exports being incompatible with `patch`, in addition to fixing that bug about commit messages being truncated when they have a `---` line.