[PATCH v3 2/3] completion: complete tracked paths for "git checkout"

When completing arguments for "git checkout", _git_checkout()
delegates to __git_complete_refs(), which only completes revision
references.  This is good, as mixing revisions and paths in a single
list from which the user can choose is confusing.  However, if no
reference matches, or if "--" is given, _git_checkout() leaves
COMPREPLY empty.  Bash then falls back to the default filename
completion in $PWD.

This fails when "git -C <path>" is used, as $PWD is not the target
repository.

Update _git_checkout() to use __git_complete_index_file() when "--"
is present, or when revision reference completion yields no matching
candidates, so that tracked paths are offered as candidates.

Signed-off-by: Junio C Hamano <[email protected]>
---
 contrib/completion/git-completion.bash |  4 +++
 t/t9902-completion.sh                  | 39 ++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index 38dec1cabe..0eecfcbf8b 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -1780,6 +1780,10 @@ _git_checkout ()
 			;;
 		esac
 	fi
+
+	if [ ${#COMPREPLY[@]} -eq 0 ]; then
+		__git_complete_index_file ""
+	fi
 }
 
 __git_sequencer_inprogress_options="--continue --quit --abort --skip"
diff --git a/t/t9902-completion.sh b/t/t9902-completion.sh
index b889ec8c77..13fa5c65c3 100755
--- a/t/t9902-completion.sh
+++ b/t/t9902-completion.sh
@@ -2714,6 +2714,45 @@ test_expect_success 'git -C <path> checkout uses the right repo' '
 	EOF
 '
 
+test_expect_success 'git checkout completes tracked paths when no refs match' '
+	# file1 and file2 are tracked but file3 is not
+	# there is no ref that begins with f
+	test_completion "git checkout f" <<-\EOF &&
+	file1
+	file2
+	EOF
+	test_completion "git checkout -- f" <<-\EOF
+	file1
+	file2
+	EOF
+'
+
+test_expect_success 'git -C <path> checkout completes paths in specified repo' '
+	# otherfile is tracked, oops is not
+	# lostfile is tracked but lost
+	test_when_finished "rm -rf repo-for-checkout" &&
+	git init repo-for-checkout &&
+	echo content >repo-for-checkout/otherfile &&
+	echo content >repo-for-checkout/lostfile &&
+	git -C repo-for-checkout add otherfile &&
+	git -C repo-for-checkout add lostfile &&
+	git -C repo-for-checkout commit -m otherfile &&
+	echo untracked >repo-for-checkout/oops &&
+	rm -f repo-for-checkout/lostfile &&
+	test_completion "git -C repo-for-checkout checkout o" <<-\EOF &&
+	otherfile
+	EOF
+	test_completion "git -C repo-for-checkout checkout -- o" <<-\EOF &&
+	otherfile
+	EOF
+	test_completion "git -C repo-for-checkout checkout l" <<-\EOF &&
+	lostfile
+	EOF
+	test_completion "git -C repo-for-checkout checkout -- l" <<-\EOF
+	lostfile
+	EOF
+'
+
 test_expect_success 'git diff completes tracked paths when no refs match' '
 	# file1 and file2 are tracked but file3 is not
 	# there is no ref that begins with f
-- 
2.55.0-759-g9dcc51a0fd