Man writer: use default middle header when calling .TH when metadata does not include one

[dimztimz]

Explain the problem.

The following input:

---
title: HELLO
section: 1
---

# DESCRIPTION

hello world

Using the following command line: pandoc --from markdown --to man --standalone

Produces the following output:

.TH "HELLO" "1" "" "" ""
.SH DESCRIPTION
hello world

What I expect is that the last argument to the .TH macro to be omitted:

.TH "HELLO" "1" "" ""

Pandoc version?

Tested with v3.1.3, but also on online version

Rationale

The .TH macro has some optional arguments. See groff_man(7) and man-pages(7). If the last argument is omitted, the header in the rendered man-page will be the default one which depends on the section number. See relevant quotes:

.TH identifier section [footer-middle [footer-inside [header-middle]]]
...
header-middle is centered in the header. If section is an integer between 1 and 9 (inclusive), there is no need to specify header-middle; an.tmac will supply text for it.

The first command in a man page should be a TH command:

.TH title section date source manual-section
...
manual-section: Normally, this should be empty, since the default value will be good.

More insight

See following line in the template for standalone output:

pandoc/data/templates/default.man

Line 11 in c723014

.TH "$title/nowrap$" "$section/nowrap$" "$date/nowrap$" "$footer/nowrap$" "$header/nowrap$"

Is it possible to change this so that if the variable header is undefined, then the last argument is omitted instead of writing empty double quotes ("")?