patchbomb: fix From_ in the message's envelope
Localized date in the From_ prevents MUAs like mutt from parsing mbox files
generated by patchbomb. Using a 24 characters date in asctime format instead.
#!/bin/sh
hg init
touch a
hg add a
hg ci -m "a" -d "1000000 0"
echo 123 > b
hg add b
hg diff --nodates
hg diff --nodates -r tip
echo foo > a
hg diff --nodates
hg diff -r ""
hg diff -r tip -r ""
true