t0302: test credential-store support for XDG_CONFIG_HOME

t0302 now tests git-credential-store's support for the XDG user-specific
configuration file $XDG_CONFIG_HOME/git/credentials. Specifically:

* Ensure that the XDG file is strictly opt-in. It should not be created
  by git at all times if it does not exist.

* Conversely, if the XDG file exists, ~/.git-credentials should
  not be created at all times.

* If both the XDG file and ~/.git-credentials exists, then both files
  should be used for credential lookups. However, credentials should
  only be written to ~/.git-credentials.

* Credentials must be erased from both files.

* $XDG_CONFIG_HOME can be a custom directory set by the user as per the
  XDG base directory specification. Test that git-credential-store
  respects that, but defaults to "~/.config/git/credentials" if it does
  not exist or is empty.

Helped-by: Matthieu Moy <Matthieu.Moy@grenoble-inp.fr>
Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Paul Tan <pyokagan@gmail.com>
Reviewed-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t0302-credential-store.sh

@@ -6,4 +6,118 @@ test_description='credential-store tests'
 
 helper_test store
 
+test_expect_success 'when xdg file does not exist, xdg file not created' '
+	test_path_is_missing "$HOME/.config/git/credentials" &&
+	test -s "$HOME/.git-credentials"
+'
+
+test_expect_success 'setup xdg file' '
+	rm -f "$HOME/.git-credentials" &&
+	mkdir -p "$HOME/.config/git" &&
+	>"$HOME/.config/git/credentials"
+'
+
+helper_test store
+
+test_expect_success 'when xdg file exists, home file not created' '
+	test -s "$HOME/.config/git/credentials" &&
+	test_path_is_missing "$HOME/.git-credentials"
+'
+
+test_expect_success 'setup custom xdg file' '
+	rm -f "$HOME/.git-credentials" &&
+	rm -f "$HOME/.config/git/credentials" &&
+	mkdir -p "$HOME/xdg/git" &&
+	>"$HOME/xdg/git/credentials"
+'
+
+XDG_CONFIG_HOME="$HOME/xdg"
+export XDG_CONFIG_HOME
+helper_test store
+unset XDG_CONFIG_HOME
+
+test_expect_success 'if custom xdg file exists, home and xdg files not created' '
+	test_when_finished "rm -f $HOME/xdg/git/credentials" &&
+	test -s "$HOME/xdg/git/credentials" &&
+	test_path_is_missing "$HOME/.git-credentials" &&
+	test_path_is_missing "$HOME/.config/git/credentials"
+'
+
+test_expect_success 'get: use home file if both home and xdg files have matches' '
+	echo "https://home-user:home-pass@example.com" >"$HOME/.git-credentials" &&
+	mkdir -p "$HOME/.config/git" &&
+	echo "https://xdg-user:xdg-pass@example.com" >"$HOME/.config/git/credentials" &&
+	check fill store <<-\EOF
+	protocol=https
+	host=example.com
+	--
+	protocol=https
+	host=example.com
+	username=home-user
+	password=home-pass
+	--
+	EOF
+'
+
+test_expect_success 'get: use xdg file if home file has no matches' '
+	>"$HOME/.git-credentials" &&
+	mkdir -p "$HOME/.config/git" &&
+	echo "https://xdg-user:xdg-pass@example.com" >"$HOME/.config/git/credentials" &&
+	check fill store <<-\EOF
+	protocol=https
+	host=example.com
+	--
+	protocol=https
+	host=example.com
+	username=xdg-user
+	password=xdg-pass
+	--
+	EOF
+'
+
+test_expect_success 'get: use xdg file if home file is unreadable' '
+	echo "https://home-user:home-pass@example.com" >"$HOME/.git-credentials" &&
+	chmod -r "$HOME/.git-credentials" &&
+	mkdir -p "$HOME/.config/git" &&
+	echo "https://xdg-user:xdg-pass@example.com" >"$HOME/.config/git/credentials" &&
+	check fill store <<-\EOF
+	protocol=https
+	host=example.com
+	--
+	protocol=https
+	host=example.com
+	username=xdg-user
+	password=xdg-pass
+	--
+	EOF
+'
+
+test_expect_success 'store: if both xdg and home files exist, only store in home file' '
+	>"$HOME/.git-credentials" &&
+	mkdir -p "$HOME/.config/git" &&
+	>"$HOME/.config/git/credentials" &&
+	check approve store <<-\EOF &&
+	protocol=https
+	host=example.com
+	username=store-user
+	password=store-pass
+	EOF
+	echo "https://store-user:store-pass@example.com" >expected &&
+	test_cmp expected "$HOME/.git-credentials" &&
+	test_must_be_empty "$HOME/.config/git/credentials"
+'
+
+
+test_expect_success 'erase: erase matching credentials from both xdg and home files' '
+	echo "https://home-user:home-pass@example.com" >"$HOME/.git-credentials" &&
+	mkdir -p "$HOME/.config/git" &&
+	echo "https://xdg-user:xdg-pass@example.com" >"$HOME/.config/git/credentials" &&
+	check reject store <<-\EOF &&
+	protocol=https
+	host=example.com
+	EOF
+	test_must_be_empty "$HOME/.git-credentials" &&
+	test_must_be_empty "$HOME/.config/git/credentials"
+'
+
 test_done