config: test home and xdg files in list --global

The `git config list --global` output includes `$HOME/.gitconfig`, but
ignores `$XDG_CONFIG_HOME/git/config`. It should include both files.

Modify tests to check for this expected behavior:
    A. `git config list --global` should include contents from both the
       home and XDG config locations (assuming they are readable), not
       just the former.

Also, add tests to ensure that the subsequence patches do not introduce
regressions on the behavior of `git config list`:
    B. The home config should take precedence over the XDG config.

    C. Without `--global`, it should not bail on unreadable/non-existent
       global config files.

    D. With `--global`, it should bail when both `$HOME/.gitconfig` and
       `$XDG_CONFIG_HOME/git/config` are unreadable. It should not bail
       if at least one of them is readable.

Signed-off-by: Delilah Ashley Wu <[email protected]>

Author: delilahw

t/t1300-config.sh

@@ -2367,6 +2367,71 @@ test_expect_success '--show-scope with --default' '
 	test_cmp expect actual
 '
 
+test_expect_success 'list with nonexistent global config' '
+	rm -rf "$HOME"/.gitconfig "$HOME"/.config/git/config &&
+	git config ${mode_prefix}list --show-scope
+'
+
+test_expect_success 'list --global with nonexistent global config' '
+	rm -rf "$HOME"/.gitconfig "$HOME"/.config/git/config &&
+	test_must_fail git config ${mode_prefix}list --global --show-scope
+'
+
+test_expect_success 'list --global with only home' '
+	rm -rf "$HOME"/.config/git/config &&
+
+	test_when_finished rm -f \"\$HOME\"/.gitconfig &&
+	cat >"$HOME"/.gitconfig <<-EOF &&
+	[home]
+		config = true
+	EOF
+
+	cat >expect <<-EOF &&
+	global	home.config=true
+	EOF
+	git config ${mode_prefix}list --global --show-scope >output &&
+	test_cmp expect output
+'
+
+test_expect_success 'list --global with only xdg' '
+	rm -f "$HOME"/.gitconfig &&
+
+	test_when_finished rm -rf \"\$HOME\"/.config/git &&
+	mkdir -p "$HOME"/.config/git &&
+	cat >"$HOME"/.config/git/config <<-EOF &&
+	[xdg]
+		config = true
+	EOF
+
+	cat >expect <<-EOF &&
+	global	xdg.config=true
+	EOF
+	git config ${mode_prefix}list --global --show-scope >output &&
+	test_cmp expect output
+'
+
+test_expect_success 'list --global with both home and xdg' '
+	test_when_finished rm -f \"\$HOME\"/.gitconfig &&
+	cat >"$HOME"/.gitconfig <<-EOF &&
+	[home]
+		config = true
+	EOF
+
+	test_when_finished rm -rf \"\$HOME\"/.config/git &&
+	mkdir -p "$HOME"/.config/git &&
+	cat >"$HOME"/.config/git/config <<-EOF &&
+	[xdg]
+		config = true
+	EOF
+
+	cat >expect <<-EOF &&
+	global	xdg.config=true
+	global	home.config=true
+	EOF
+	git config ${mode_prefix}list --global --show-scope >output &&
+	test_cmp expect output
+'
+
 test_expect_success 'override global and system config' '
 	test_when_finished rm -f \"\$HOME\"/.gitconfig &&
 	cat >"$HOME"/.gitconfig <<-EOF &&

t/t1306-xdg-files.sh

@@ -68,7 +68,8 @@ test_expect_success 'read with --list: xdg file exists and ~/.gitconfig exists'
 	>.gitconfig &&
 	echo "[user]" >.gitconfig &&
 	echo "	name = read_gitconfig" >>.gitconfig &&
-	echo user.name=read_gitconfig >expected &&
+	echo user.name=read_config >expected &&
+	echo user.name=read_gitconfig >>expected &&
 	git config --global --list >actual &&
 	test_cmp expected actual
 '