Subject of notification email too long - add limit

[trac-trac@…]

I received a Trac notification email with a subject line like this:

[Pidgin] Batch modify: #4933, #5329, #5583, #5696, #6521, #6751,
 #6881, #6988, #7110, #7145, #7304, #7626, #7999, #8023, #8040,
 #8075, #8135, #8201, #8220, #8238, #8321, #8323, #8341, #8369,
 #8371, #8382, #8388, #8414, #8467, #8507, #8547, #8564, #8599,
 #8630, #8647, #8656, #8680, #8689, #8699, #8701, #8714, #8753,
 #8778, #8788, #8829, #8854, #8919, #8967, #8984, #8993, #9009,
 #9020, #9035, #9043, #9077, #9099, #9110, #9136, #9144, #9163,
 #9167, #9185, #9189, #9194, #9195, #9201, #9225, #9230, #9237,
...

The total length of the subject line was 5546 characters. Such long subject lines are not well-handled by email clients. Eg. Thunderbird doesn't allow the message to be viewed without a workaround. Trac should impose some hard limit on the length of the subject line for all emails. Subjects longer than that should be truncated with "…" appended.

For this specific email (batch-modification) I'd also suggest not listing all ticket numbers in the subject line if there are more than X of them.