Redmine

Currently, Redmine uses user names for user columns for CSV exports.
However, Redmine Importer expects login instead of user names for CSV import.
(cf. https://github.com/leovitch/redmine_importer/issues/22 )

To fix this, one solution is to change Redmine Importer to use user names.
However, we have two drawbacks:

• User names may conflicts to other users, so we cannot identify a user by a user name.
• User names may change after export, so user may not found for a user name when we import later.

So, I think it's better to change Redmine to use login instead of user name for CSV export.
One drawback is what we get is not what we see anymore, we see user names on web pages,
but we see logins on CSV files. But I think it's a reasonable tradeoff.

What do you think?