completion: handle unusual characters for sparse-checkout

Update the __gitcomp_directories method to de-quote and handle unusual
characters in directory names. Although this initially involved an attempt
to re-use the logic in __git_index_files, this method removed
subdirectories (e.g. folder1/0/ became folder1/), so instead new custom
logic was placed directly in the __gitcomp_directories method.

Note there are two tests for this new functionality - one for spaces and
accents and one for backslashes and tabs. The backslashes and tabs test
uses FUNNYNAMES to avoid running on Windows. This is because:

1. Backslashes are explicitly not allowed in Windows file paths.
2. Although tabs appear to be allowed when creating a file in a Windows
bash shell, they actually are not renderable (and appear as empty boxes
in the shell).

Co-authored-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Co-authored-by: Lessley Dennington <lessleydennington@gmail.com>
Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Lessley Dennington <lessleydennington@gmail.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -2988,7 +2988,7 @@ _git_show_branch ()
 
 __gitcomp_directories ()
 {
-	local _tmp_dir _tmp_completions
+	local _tmp_dir _tmp_completions _found=0
 
 	# Get the directory of the current token; this differs from dirname
 	# in that it keeps up to the final trailing slash.  If no slash found
@@ -2996,20 +2996,18 @@ __gitcomp_directories ()
 	[[ "$cur" =~ .*/ ]]
 	_tmp_dir=$BASH_REMATCH
 
-	# Find possible directory completions, adding trailing '/' characters
-	_tmp_completions="$(git ls-tree -d --name-only HEAD $_tmp_dir |
-		sed -e s%$%/%)"
-
-	if [[ -n "$_tmp_completions" ]]; then
-		# There were some directory completions, so find ones that
-		# start with "$cur", the current token, and put those in COMPREPLY
-		local i=0 c IFS=$' \t\n'
-		for c in $_tmp_completions; do
+	# Find possible directory completions, adding trailing '/' characters,
+	# de-quoting, and handling unusual characters.
+	while IFS= read -r -d $'\0' c ; do
+		# If there are directory completions, find ones that start
+		# with "$cur", the current token, and put those in COMPREPLY
 		if [[ $c == "$cur"* ]]; then
-			COMPREPLY+=("$c")
+			COMPREPLY+=("$c/")
+			_found=1
 		fi
-		done
-	elif [[ "$cur" =~ /$ ]]; then
+	done < <(git ls-tree -z -d --name-only HEAD $_tmp_dir)
+
+	if [[ $_found == 0 ]] && [[ "$cur" =~ /$ ]]; then
 		# No possible further completions any deeper, so assume we're at
 		# a leaf directory and just consider it complete
 		__gitcomp_direct_append "$cur "

t/t9902-completion.sh

@@ -1505,6 +1505,55 @@ test_expect_success 'cone mode sparse-checkout completes directory names' '
 	)
 '
 
+test_expect_success 'cone mode sparse-checkout completes directory names with spaces and accents' '
+	# reset sparse-checkout
+	git -C sparse-checkout sparse-checkout disable &&
+	(
+		cd sparse-checkout &&
+		mkdir "directory with spaces" &&
+		mkdir "directory-with-áccent" &&
+		>"directory with spaces/randomfile" &&
+		>"directory-with-áccent/randomfile" &&
+		git add . &&
+		git commit -m "Add directory with spaces and directory with accent" &&
+		git sparse-checkout set --cone "directory with spaces" \
+			"directory-with-áccent" &&
+		test_completion "git sparse-checkout add dir" <<-\EOF &&
+		directory with spaces/
+		directory-with-áccent/
+		EOF
+		rm -rf "directory with spaces" &&
+		rm -rf "directory-with-áccent" &&
+		git add . &&
+		git commit -m "Remove directory with spaces and directory with accent"
+	)
+'
+
+# use FUNNYNAMES to avoid running on Windows, which doesn't permit backslashes or tabs in paths
+test_expect_success FUNNYNAMES 'cone mode sparse-checkout completes directory names with backslashes and tabs' '
+	# reset sparse-checkout
+	git -C sparse-checkout sparse-checkout disable &&
+	(
+		cd sparse-checkout &&
+		mkdir "directory\with\backslashes" &&
+		mkdir "$(printf "directory\twith\ttabs")" &&
+		>"directory\with\backslashes/randomfile" &&
+		>"$(printf "directory\twith\ttabs")/randomfile" &&
+		git add . &&
+		git commit -m "Add directory with backslashes and directory with tabs" &&
+		git sparse-checkout set --cone "directory\with\backslashes" \
+			"$(printf "directory\twith\ttabs")" &&
+		test_completion "git sparse-checkout add dir" <<-\EOF &&
+		directory\with\backslashes/
+		directory	with	tabs/
+		EOF
+		rm -rf "directory\with\backslashes" &&
+		rm -rf "$(printf "directory\twith\ttabs")" &&
+		git add . &&
+		git commit -m "Remove directory with backslashes and directory with tabs"
+	)
+'
+
 test_expect_success 'non-cone mode sparse-checkout uses bash completion' '
 	# reset sparse-checkout repo to non-cone mode
 	git -C sparse-checkout sparse-checkout disable &&