If several values for Iptc.Application2.Keywords are entered in an .exv-file, only one of them will be inserted

[norbertwg]

Describe the bug

The insert command does not insert all values for Iptc.Application2.Keywords, but only one.

To Reproduce

Starting with an image having "first" and "second" entered as Iptc.Application2.Keywords.
Using exiv2 -ea an .exv-file is created. This file still has both values of Iptc.Application2.Keywords.
Using exiv2 -ia the data from .exv-file are inserted again. Now Iptc.Application2.Keywords contains only "second".
If all values for Iptc.Application2.Keywords are deleted before insert, the result is the same.

I am using branch main, commit 4e28dc9

Expected behavior

All values for Iptc.Application2.Keywords should be inserted.

Desktop (please complete the following information):

• OS Windows 11
• Exiv2 version and source: 1.00.0.9, built using above mentioned commit
• Compiler and version: MSVC 2022)
• Compilation mode and/or compiler flags: Release

[norbertwg]

I tried a little bit more and perhaps these results help investigating the issue. Start with an image without Iptc.Application2.Keywords.
>exiv2 -M"add Iptc.Application2.Keywords one" e.jpg
>exiv2 -M"add Iptc.Application2.Keywords two" e.jpg
>exiv2 -PI -g Keywords e.jpg
Iptc.Application2.Keywords String 3 one
Iptc.Application2.Keywords String 3 two
Now export and import:
>exiv2 -ea e.jpg
>exiv2 -ia e.jpg
>exiv2 -PI -g Keywords e.jpg
Iptc.Application2.Keywords String 3 two
Iptc.Application2.Keywords String 3 two

Another test, now with four key words:
>exiv2 -PI -g Keywords f.jpg
Iptc.Application2.Keywords String 3 one
Iptc.Application2.Keywords String 3 two
Iptc.Application2.Keywords String 5 three
Iptc.Application2.Keywords String 4 four
>exiv2 -ea f.jpg
>exiv2 -ia f.jpg
>exiv2 -PI -g Keywords f.jpg
Iptc.Application2.Keywords String 4 four
Iptc.Application2.Keywords String 3 two
Iptc.Application2.Keywords String 5 three
Iptc.Application2.Keywords String 4 four

After export and import the value for first keyword is overwritten with value of last.
Tried the same with Iptc.Application2.Byline, Same result.
Export and Import of multiple values of type XmpSeq works fine.