TFS allows certain entitled users to perform checkins on behalf of another user
using the /author command-line switch (see: http://msdn.microsoft.com/en-
us/library/c327ca1z(VS.80).aspx). When the tf history command is run, the
history records for files checked-in in this manner have an extra line of
information between the "User" and "Date" lines, which reports the name of the
user who actually checked the content in.

For example, the following two (sanitized) records were returned from tf
history, where CS45212 was checked-in using the /author switch and CS15005 was
checked-in without the /author switch:

-------------------------------------------------------------------------------
Changeset: 45212
User: USERA
Checked in by: USERB
Date: Tuesday, November 24, 2009 10:59:13 AM

Comment:
Sample checkin with /author

Items:
edit $/PROJECT/PATH/TO/FILE.txt

Policy Warnings:
Override Reason:
XXXX XXXXXXX XX XXXXX
Messages:
XXXXXXXX XXXXX XX XXXXXXXX XXXXXXX XXXX.
XXXXXXXX XXXXX XX XXXXXXXX XX XXXXXXX.

-------------------------------------------------------------------------------
Changeset: 15005
User: USERC
Date: Monday, April 06, 2009 8:29:28 AM

Comment:
Sample normal checkin (without /author)

Items:
edit $/PROJECT/PATH/TO/FILE.txt

Check-in Notes:
XXXXXXX XXXX:
XXXXXXX XXXXXX
XXXX XXXXXXXXXXX:
XXXXXX, XXXX;
XXXXXXX XXXXX XXX:
X
XXXXXXXX XXXXXXXXX:
XX XXXXXXXXX:

When we hit a checkin performed with the /author switch, the tfs plugin is
trying to parse the "Checked in by" as a date and reports a failed source
retrieval with the following message:

FATAL: Unparseable date: "USERB"