lib-gpg: allow tests with GPGSM or GPGSSH prereq first

When the 'GPG' prereq is lazily tested, `mkdir "$GNUPGHOME"` could
fail if the "$GNUPGHOME" directory already exists. This can happen if
the 'GPGSM' or the 'GPGSSH' prereq has been lazily tested before as they
already create "$GNUPGHOME".

To allow the GPGSM or the GPGSSH prereq to appear before the GPG prereq
in some test scripts, let's refactor the creation and setup of the
"$GNUPGHOME"` directory in a new prepare_gnupghome() function that uses
`mkdir -p "$GNUPGHOME"`.

This will be useful in a following commit.

Unfortunately the new prepare_gnupghome() function cannot be used when
lazily testing the GPG2 prereq, because that would expose existing,
hidden bugs in "t1016-compatObjectFormat.sh", so let's just document
that with a NEEDSWORK comment.

Helped-by: Todd Zullinger <tmz@pobox.com>
Helped-by: Collin Funk <collin.funk1@gmail.com>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: chriscool

t/lib-gpg.sh

@@ -9,6 +9,16 @@
 GNUPGHOME="$(pwd)/gpghome"
 export GNUPGHOME
 
+# All the "test_lazy_prereq GPG*" below should use
+# `prepare_gnupghome()` either directly or through a call to
+# `test_have_prereq GPG*`. That's because `gpg` and `gpgsm`
+# only create the directory specified using "$GNUPGHOME" or
+# `--homedir` if it's the default (usually "~/.gnupg").
+prepare_gnupghome() {
+	mkdir -p "$GNUPGHOME" &&
+	chmod 0700 "$GNUPGHOME"
+}
+
 test_lazy_prereq GPG '
 	gpg_version=$(gpg --version 2>&1)
 	test $? != 127 || exit 1
@@ -38,8 +48,7 @@ test_lazy_prereq GPG '
 		# To export ownertrust:
 		#	gpg --homedir /tmp/gpghome --export-ownertrust \
 		#		> lib-gpg/ownertrust
-		mkdir "$GNUPGHOME" &&
-		chmod 0700 "$GNUPGHOME" &&
+		prepare_gnupghome &&
 		(gpgconf --kill all || : ) &&
 		gpg --homedir "${GNUPGHOME}" --import \
 			"$TEST_DIRECTORY"/lib-gpg/keyring.gpg &&
@@ -63,6 +72,14 @@ test_lazy_prereq GPG2 '
 		;;
 	*)
 		(gpgconf --kill all || : ) &&
+
+		# NEEDSWORK: prepare_gnupghome() should definitely be
+		# called here, but it looks like it exposes a
+		# pre-existing, hidden bug by allowing some tests in
+		# t1016-compatObjectFormat.sh to run instead of being
+		# skipped. See:
+		# https://lore.kernel.org/git/ZoV8b2RvYxLOotSJ@teonanacatl.net/
+
 		gpg --homedir "${GNUPGHOME}" --import \
 			"$TEST_DIRECTORY"/lib-gpg/keyring.gpg &&
 		gpg --homedir "${GNUPGHOME}" --import-ownertrust \
@@ -132,8 +149,7 @@ test_lazy_prereq GPGSSH '
 	test $? = 0 || exit 1;
 
 	# Setup some keys and an allowed signers file
-	mkdir -p "${GNUPGHOME}" &&
-	chmod 0700 "${GNUPGHOME}" &&
+	prepare_gnupghome &&
 	(setfacl -k "${GNUPGHOME}" 2>/dev/null || true) &&
 	ssh-keygen -t ed25519 -N "" -C "git ed25519 key" -f "${GPGSSH_KEY_PRIMARY}" >/dev/null &&
 	ssh-keygen -t rsa -b 2048 -N "" -C "git rsa2048 key" -f "${GPGSSH_KEY_SECONDARY}" >/dev/null &&