Re: git-send-email creates duplicate Message-Id's

Junio C Hamano
2007-09-17T20:22:36Z

Adrian Bunk <bunk@kernel.org> writes:

> The following might be a bug in git-send-email (git maintainers Cc'ed
> and KVM list removed from Cc):
>
> Patch 54 got the same Message-Id as patch 61 and patch 89 got the same
> Message-Id as patch 104.
> ...
> The emails are:
> http://marc.info/?l=linux-kernel&m=119002061330270&w=2
> http://marc.info/?l=linux-kernel&m=119002059626434&w=2
> http://marc.info/?l=linux-kernel&m=119002060011801&w=2
> http://marc.info/?l=linux-kernel&m=119002060318915&w=2

The old code generated rand(4200) for each message and appended
it to the timestamp. I do not know where the original author
got 4200 from, but I think if you send many messages within a
single second it is possible to get collisions.

I guess something like this patch is an improvement? It
generates a single prefix from timestamp and random, and appends
a number that is incremented for each message.

---
diff --git a/git-send-email.perl b/git-send-email.perl
index dd7560b..e250732 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -477,10 +477,18 @@ sub extract_valid_address {

# We'll setup a template for the message id, using the "from" address:

+my ($message_id_stamp, $message_id_serial);
sub make_message_id
{
- my $date = time;
- my $pseudo_rand = int (rand(4200));
+ my $uniq;
+ if (!defined $message_id_stamp) {
+ $message_id_stamp = sprintf("%s-%s", time, int(rand(4200)));
+ $message_id_serial = 0;
+ }
+ $message_id_serial++;
+
+ $uniq = "$message_id_stamp-$message_id_serial";
+
my $du_part;
for ($sender, $repocommitter, $repoauthor) {
$du_part = extract_valid_address(sanitize_address($_));
@@ -490,8 +498,8 @@ sub make_message_id
use Sys::Hostname qw();
$du_part = 'user@' . Sys::Hostname::hostname();
}
- my $message_id_template = "<%s-git-send-email-$du_part>";
- $message_id = sprintf $message_id_template, "$date$pseudo_rand";
+ my $message_id_template = "<%s-git-send-email-%s>";
+ $message_id = sprintf($message_id_template, $uniq, $du_part);
#print "new message id = $message_id\n"; # Was useful for debugging
}