MANIFEST       | 1 +
 t/.gitconfig   | 4 ++++
 t/purge.t      | 1 +
 t/replace.t    | 3 +++
 t/v2mirror.t   | 2 ++
 t/v2writable.t | 2 ++

diff --git a/MANIFEST b/MANIFEST
index 689d3d4ee21fb5fcc7ebec07ea206de6dc2de381..9475667b6620af3abd06af90da8e843a4df7549d 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -194,6 +194,7 @@ scripts/report-spam
 scripts/slrnspool2maildir
 scripts/ssoma-replay
 scripts/xhdr-num2mid
+t/.gitconfig
 t/address.t
 t/admin.t
 t/altid.t
diff --git a/t/.gitconfig b/t/.gitconfig
new file mode 100644
index 0000000000000000000000000000000000000000..645a304167ea51802894ac7b823b14b953a476d3
--- /dev/null
+++ b/t/.gitconfig
@@ -0,0 +1,4 @@
+; this becomes ~/.gitconfig for tests where we use
+; "$ENV{HOME} = '/path/to/worktree/t'" in tests
+[gc]
+	writeCommitGraph = false
diff --git a/t/purge.t b/t/purge.t
index 12644d691f038b3034c97280fb45a3e557f2fc14..db09b731f9cf871d717f6088e7240386c100975a 100644
--- a/t/purge.t
+++ b/t/purge.t
@@ -11,6 +11,7 @@ 	eval "require $mod";
 	plan skip_all => "missing $mod for t/purge.t" if $@;
 };
 use Cwd qw(abs_path); # we need this since we chdir below
+local $ENV{HOME} = abs_path('t');
 my $purge = abs_path('blib/script/public-inbox-purge');
 my ($tmpdir, $for_destroy) = tmpdir();
 use_ok 'PublicInbox::V2Writable';
diff --git a/t/replace.t b/t/replace.t
index 039c6bc6fde54d21eb3558f3ab61c47e8e3b49dd..e9361856aa0c9409f2389caf06f68c1401c9f381 100644
--- a/t/replace.t
+++ b/t/replace.t
@@ -6,11 +6,14 @@ use Test::More;
 use PublicInbox::MIME;
 use PublicInbox::InboxWritable;
 require './t/common.perl';
+use Cwd qw(abs_path);
 require_git(2.6); # replace is v2 only, for now...
 foreach my $mod (qw(DBD::SQLite)) {
 	eval "require $mod";
 	plan skip_all => "$mod missing for $0" if $@;
 }
+
+local $ENV{HOME} = abs_path('t');
 
 sub test_replace ($$$) {
 	my ($v, $level, $opt) = @_;
diff --git a/t/v2mirror.t b/t/v2mirror.t
index 96657fdc830755b26bc8bbf4c6bf6389126fe598..a45a262e59dc7c16ee1b3c7564ddaae8d52e4155 100644
--- a/t/v2mirror.t
+++ b/t/v2mirror.t
@@ -4,7 +4,9 @@ use strict;
 use warnings;
 use Test::More;
 require './t/common.perl';
+use Cwd qw(abs_path);
 require_git(2.6);
+local $ENV{HOME} = abs_path('t');
 
 # Integration tests for HTTP cloning + mirroring
 foreach my $mod (qw(Plack::Util Plack::Builder
diff --git a/t/v2writable.t b/t/v2writable.t
index 7519b4878585746851526cd998d0828106d91168..8bbcd45aad808e3701953bf7e5e7057173cd7185 100644
--- a/t/v2writable.t
+++ b/t/v2writable.t
@@ -6,11 +6,13 @@ use Test::More;
 use PublicInbox::MIME;
 use PublicInbox::ContentId qw(content_digest);
 require './t/common.perl';
+use Cwd qw(abs_path);
 require_git(2.6);
 foreach my $mod (qw(DBD::SQLite Search::Xapian)) {
 	eval "require $mod";
 	plan skip_all => "$mod missing for nntpd.t" if $@;
 }
+local $ENV{HOME} = abs_path('t');
 use_ok 'PublicInbox::V2Writable';
 umask 007;
 my ($inboxdir, $for_destroy) = tmpdir();