completion: ensure that the repository path given on the command line exists

The __gitdir() helper function prints the path to the git repository
to its stdout or stays silent and returns with error when it can't
find a repository or when the repository given via $GIT_DIR doesn't
exist.

This is not the case, however, when the path in $__git_dir, i.e. the
path to the repository specified on the command line via 'git
--git-dir=<path>', doesn't exist: __gitdir() still outputs it as if it
were a real existing repository, making some completion functions
believe that they operate on an existing repository.

Check that the path in $__git_dir exists and return with error without
printing anything to stdout if it doesn't.

Signed-off-by: SZEDER Gábor <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: szeder

contrib/completion/git-completion.bash

@@ -40,6 +40,7 @@ __gitdir ()
 {
 	if [ -z "${1-}" ]; then
 		if [ -n "${__git_dir-}" ]; then
+			test -d "$__git_dir" || return 1
 			echo "$__git_dir"
 		elif [ -n "${GIT_DIR-}" ]; then
 			test -d "${GIT_DIR-}" || return 1

t/t9902-completion.sh

@@ -211,6 +211,14 @@ test_expect_success '__gitdir - $GIT_DIR set while .git directory in parent' '
 	test_cmp expected "$actual"
 '
 
+test_expect_success '__gitdir - non-existing path in $__git_dir' '
+	(
+		__git_dir="non-existing" &&
+		test_must_fail __gitdir >"$actual"
+	) &&
+	test_must_be_empty "$actual"
+'
+
 test_expect_success '__gitdir - non-existing $GIT_DIR' '
 	(
 		GIT_DIR="$ROOT/non-existing" &&