[File] Regression in ppm dimension determination

[Christoph Biedl]

Hello,

his commit

    commit 30c4d1fc3c3dfca143d587ec0608c6450d063a82 (refs/bisect/bad)
    Author: Christos Zoulas <christos at zoulas.com>
    Date:   Fri Dec 17 14:42:50 2021 +0000

        PR/304: zachs18: Allow whitespace in netpbm sizes.

introduced a regression with one of my ppm test samples. The sample
boils down to (first lines):

===================================================================
P3
# CREATOR: GIMP PNM Filter Version 1.1
10 20
255
255
(...)
===================================================================

... and the comment in line 2 ending in a number causes the enhanced
regular expression to match, resulting in

| NetPbm image data, size = 1 x 10, pixmap, ASCII text

instead of

| NetPbm image data, size = 10 x 20, pixmap, ASCII text

As I understand the format descriptions, a newline character is indeed
allowed between the two numbers that describe the image's dimensions,
so I'm not aware of an easy solution for this.

    Christoph