Re: [PATCH 1/2] t7900: adapt some tests to use a throwaway repository

Many of the tests in t7900 operate inside the main trash repository
that's set up by default by our test suite. This is overall quite
fragile as we're exercising repository maintenance in those tests, and
maintenance is of course intricately tied towards the on-disk state of a
repository. Consequently, the tests can easily impact one another.

Furthermore, in the next commit we'll have to modify the environment in
a handful of those tests. As tests don't run in a subshell, doing so
would impact all subsequent tests by default, as well.

Adapt exactly those tests to use a throwaway repository. This makes the
tests more neatly self-contained and allows us to trivially modify the
environment in the next commit.

Signed-off-by: Patrick Steinhardt <redacted>
---
 t/t7900-maintenance.sh | 70 +++++++++++++++++++++++++++++++-------------------
 1 file changed, 43 insertions(+), 27 deletions(-)

diff --git a/t/t7900-maintenance.sh b/t/t7900-maintenance.sh
index 4238569b68..6735a9e082 100755
--- a/t/t7900-maintenance.sh
+++ b/t/t7900-maintenance.sh

@@ -67,41 +67,57 @@ test_expect_success 'run [--auto|--quiet] with gc strategy' '
 '

 test_expect_success 'maintenance.auto config option' '
-	GIT_TRACE2_EVENT="$(pwd)/default" git commit --quiet --allow-empty -m 1 &&
-	test_subcommand git maintenance run --auto --quiet --detach <default &&
-	GIT_TRACE2_EVENT="$(pwd)/true" \
-		git -c maintenance.auto=true \
-		commit --quiet --allow-empty -m 2 &&
-	test_subcommand git maintenance run --auto --quiet --detach <true &&
-	GIT_TRACE2_EVENT="$(pwd)/false" \
-		git -c maintenance.auto=false \
-		commit --quiet --allow-empty -m 3 &&
-	test_subcommand ! git maintenance run --auto --quiet --detach <false
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+
+		GIT_TRACE2_EVENT="$(pwd)/default" git commit --quiet --allow-empty -m 1 &&
+		test_subcommand git maintenance run --auto --quiet --detach <default &&
+		GIT_TRACE2_EVENT="$(pwd)/true" \
+			git -c maintenance.auto=true \
+			commit --quiet --allow-empty -m 2 &&
+		test_subcommand git maintenance run --auto --quiet --detach <true &&
+		GIT_TRACE2_EVENT="$(pwd)/false" \
+			git -c maintenance.auto=false \
+			commit --quiet --allow-empty -m 3 &&
+		test_subcommand ! git maintenance run --auto --quiet --detach <false
+	)
 '

 test_expect_success 'gc.auto config option' '
-	GIT_TRACE2_EVENT="$(pwd)/default" git commit --quiet --allow-empty -m 1 &&
-	test_subcommand git maintenance run --auto --quiet --detach <default &&
-	GIT_TRACE2_EVENT="$(pwd)/true" \
-		git -c gc.auto=1 commit --quiet --allow-empty -m 2 &&
-	test_subcommand git maintenance run --auto --quiet --detach <true &&
-	GIT_TRACE2_EVENT="$(pwd)/false" \
-		git -c gc.auto=0 commit --quiet --allow-empty -m 3 &&
-	test_subcommand ! git maintenance run --auto --quiet --detach <false
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+
+		GIT_TRACE2_EVENT="$(pwd)/default" git commit --quiet --allow-empty -m 1 &&
+		test_subcommand git maintenance run --auto --quiet --detach <default &&
+		GIT_TRACE2_EVENT="$(pwd)/true" \
+			git -c gc.auto=1 commit --quiet --allow-empty -m 2 &&
+		test_subcommand git maintenance run --auto --quiet --detach <true &&
+		GIT_TRACE2_EVENT="$(pwd)/false" \
+			git -c gc.auto=0 commit --quiet --allow-empty -m 3 &&
+		test_subcommand ! git maintenance run --auto --quiet --detach <false
+	)
 '

 test_expect_success 'maintenance.auto overrides gc.auto' '
-	test_when_finished "rm -f trace" &&
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&

-	test_config maintenance.auto false &&
-	test_config gc.auto 1 &&
-	GIT_TRACE2_EVENT="$(pwd)/trace" git commit --quiet --allow-empty -m 1 &&
-	test_subcommand ! git maintenance run --auto --quiet --detach <trace &&
+		git config set maintenance.auto false &&
+		git config set gc.auto 1 &&