Subject: Re: Release 13 of the PostgreSQL BuildFarm client
From: Andrew Dunstan <andrew@dunslane.net>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: buildfarm-members@postgresql.org
References: <18c03f7e-3ab9-f7b4-9248-feb85b0f03ed@dunslane.net>
 <1660080.1627945870@sss.pgh.pa.us>
 <5462d8bd-b8aa-3c38-b078-4bf5e94f8eba@dunslane.net>
Message-ID: <0234f0ff-221a-e6a4-39c7-137ed4edb74e@dunslane.net>
Date: Tue, 3 Aug 2021 15:14:41 -0400
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On 8/3/21 8:47 AM, Andrew Dunstan wrote:
> On 8/2/21 7:11 PM, Tom Lane wrote:
>> Andrew Dunstan <andrew@dunslane.net> writes:
>>> I have pushed Release 13 of the PostgreSQL BuildFarm client.
>> FYI, this seems to have broken compatibility with ancient versions
>> of git.  prairiedog and gaur/pademelon are both using
>> git version 1.7.9.6, and they both choked on the --prune-tags
>> option.  I tried removing that, as it seemed possibly unnecessary,
>> but it didn't improve matters.
>>
>> I suppose I'm overdue to update git on these machines, but anyone
>> else running dinosaur versions may want to be cautious.
>
> Not so much dinosaurs either. I just tried on Centos 7 which isn't that
> old, and got a failure. Not just from the prune-tags but from 'git
> ls-remote' not supporting symref. I will come up with a solution in a
> couple of days, but for now please don't deploy unless you have a fairly
> modern git. If you do deploy, be prepared to roll back.
>
>

OK, I have come up with this fix. Essentially the code detects if the
git version can run `git ls-remote --symref` and refuses to run branch
name checking code if it fails. It also outputs a warning message unless
the config setting skip_git_default_check has been explicitly set. In
either case the owner will have to update their git installation or face
a flag day event when the default branch name changes.


I have tested this on Centos 7 which has a git that's plenty old enough
to exhibit the problems Tom encountered.


I'm planning on issuing a 12.1 release fairly soon with this patch, but
as I developed it fairly quickly and through the fog of some painkillers
I'd appreciate more eyes on it first :-)


cheers


andrew


-- 

Andrew Dunstan
EDB: https://www.enterprisedb.com


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diff --git a/PGBuild/SCM.pm b/PGBuild/SCM.pm
index 8372255..5862634 100644
--- a/PGBuild/SCM.pm
+++ b/PGBuild/SCM.pm
@@ -473,7 +473,7 @@ use Fcntl qw(:flock);
 use File::Find;
 use File::Basename;
 
-use PGBuild::Utils;
+use PGBuild::Utils qw(:DEFAULT $devnull);
 use PGBuild::Options;
 
 sub new
@@ -503,6 +503,17 @@ sub new
 	}
 	$self->{target} = $target;
 	$self->{skip_git_default_check} = $conf->{skip_git_default_check} || 0;
+	if (!$self->{skip_git_default_check})
+	{
+		system("git ls-remote --symref $self->{gitrepo} HEAD > $devnull 2>&1");
+		if ($?)
+		{
+			my $gversion = `git --version`;
+			chomp $gversion;
+			print "$gversion too old to for automatic default branch update\n";
+			$self->{skip_git_default_check} = "detected by SCM module";
+		}
+	}
 	return bless $self, $class;
 }
 
@@ -720,16 +731,22 @@ sub _create_or_update_mirror
 
 	my $gitserver = $self->{gitrepo};
 
+	my $skip_default_name_check = $self->{skip_git_default_check};
+
 	my @gitlog;
 	my $status;
 	if (-d $self->{mirror})
 	{
+		# do we need --prune-tags here? I'm not sure. Only very modern versions
+		# of git have --prune-tags, so for now we'll leave it out.
+		# see https://git-scm.com/docs/git-fetch/2.25.1 for a discussion
+		# of different ways of saying it
 		@gitlog =
 		  run_log(
-			qq{git --git-dir="$self->{mirror}" fetch --prune --prune-tags});
+			qq{git --git-dir="$self->{mirror}" fetch --prune});
 		$status = $self->{ignore_mirror_failure} ? 0 : $? >> 8;
 
-		if (!$status)
+		if (!$status && !$skip_default_name_check)
 		{
 			# make sure we have the same idea of the default branch name
 			# as upstream

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