t/t-{checkout,pull}.sh: add read-only error tests

In a previous commit in this PR we adjusted the "git lfs checkout"
and "git lfs pull" commands so that when a Git LFS object's contents
can not be written to a file in the working tree, the commands output
a detailed set of error messages rather than just the message "could
not check out <filepath>".

We now add tests to our t-checkout.sh and t-pull.sh test scripts which
validate this change.  Specifically, the new "checkout: read-only
directory" and "pull: read-only directory" tests remove write permissions
on a directory in the working tree after removing a file which is
tracked as a Git LFS object from the directory.  The tests then check
that the "git lfs checkout" and "git lfs pull" commands output a full
set of error messages when they are unable to re-create the file.

Note that for historical reasons we expect that under these conditions
the commands will return a zero exit code, indicating success, rather
than a non-zero exit code, which would indicate failure.  We may adjust
this behaviour in the future, however, so that the commands also return
a non-zero exit code in these cases.

Author: chrisd8088

t/t-checkout.sh

@@ -159,6 +159,45 @@ begin_test "checkout: outside git repository"
 )
 end_test
 
+begin_test "checkout: read-only directory"
+(
+  set -e
+
+  reponame="checkout-read-only"
+  git init "$reponame"
+  cd "$reponame"
+
+  git lfs track "*.bin"
+
+  contents="a"
+  contents_oid=$(calc_oid "$contents")
+  mkdir dir
+  printf "%s" "$contents" > dir/a.bin
+
+  git add .gitattributes dir/a.bin
+  git commit -m "add dir/a.bin"
+
+  rm dir/a.bin
+
+  chmod a-w dir
+  git lfs checkout 2>&1 | tee checkout.log
+  # Note that although the checkout command should log an error, at present
+  # we still expect a zero exit code.
+  if [ "0" -ne "${PIPESTATUS[0]}" ]; then
+    echo >&2 "fatal: expected 'git lfs checkout' to succeed ..."
+    exit 1
+  fi
+
+  assert_local_object "$contents_oid" 1
+
+  [ ! -e dir/a.bin ]
+
+  grep 'could not check out "dir/a.bin"' checkout.log
+  grep 'could not create working directory file' checkout.log
+  grep 'permission denied' checkout.log
+)
+end_test
+
 begin_test "checkout: write-only file"
 (
   set -e

t/t-pull.sh

@@ -366,6 +366,50 @@ begin_test "pull: outside git repository"
 )
 end_test
 
+begin_test "pull: read-only directory"
+(
+  set -e
+
+  reponame="pull-read-only"
+  setup_remote_repo "$reponame"
+  clone_repo "$reponame" "$reponame"
+
+  git lfs track "*.bin"
+
+  contents="a"
+  contents_oid=$(calc_oid "$contents")
+  mkdir dir
+  printf "%s" "$contents" > dir/a.bin
+
+  git add .gitattributes dir/a.bin
+  git commit -m "add dir/a.bin"
+
+  git push origin main
+
+  assert_server_object "$reponame" "$contents_oid"
+
+  rm dir/a.bin
+  delete_local_object "$contents_oid"
+
+  chmod a-w dir
+  git lfs pull 2>&1 | tee pull.log
+  # Note that although the pull command should log an error, at present
+  # we still expect a zero exit code.
+  if [ "0" -ne "${PIPESTATUS[0]}" ]; then
+    echo >&2 "fatal: expected 'git lfs pull' to succeed ..."
+    exit 1
+  fi
+
+  assert_local_object "$contents_oid" 1
+
+  [ ! -e dir/a.bin ]
+
+  grep 'could not check out "dir/a.bin"' pull.log
+  grep 'could not create working directory file' pull.log
+  grep 'permission denied' pull.log
+)
+end_test
+
 begin_test "pull with empty file doesn't modify mtime"
 (
   set -e