Write file sizes of images in checksum files with comment lines,
checksum files are in BSD-style which supports comments by starting
a line with '#'.
Example:
$ cat RHEL-7.4-20170123.n.4/compose/Server/x86_64/iso/RHEL-Server-7.4-x86_64-20170123.n.4-CHECKSUM
# RHEL-7.4-20170123.n.4-Server-x86_64-dvd1.iso: 3725590528 bytes
# RHEL-7.4-20170123.n.4-Server-x86_64-boot.iso: 377487360 bytes
SHA256 (RHEL-7.4-20170123.n.4-Server-x86_64-dvd1.iso) = fa3de37fe4b859a0285f16ea1123f44f15aec169aea84bf010aa3821bd58fc41
SHA256 (RHEL-7.4-20170123.n.4-Server-x86_64-boot.iso) = 74bf68c54665328adb08b09daf773c67e633b5907e3e2797338ab3c1b58fdf48
(No space at the start of line, because git commit message drops lines
start with '#', added one space to avoid that.)
When there are multiple checksum types specified and checksums are
written to individual files, file size of the image will also be
written to every checksum files.
Fixes: #493
Signed-off-by: Qixiang Wan <qwan@redhat.com>
40df2034a8