Heavier usage of sparse-checkouts at $DAYJOB is commencing. And an issue
with git stash apply was found.

git stash's implementation as a pipeline of forked commands presents some
problems, especially when implemented atop of three commands that all behave
differently in the presence of sparse checkouts. Add a testcase
demonstrating some issues with git stash apply in a repository with a
different set of sparse-checkout patterns at apply vs create time, clean up
the relevant section of git stash code, and incidentally fix a submodule
testcase unrelated to sparse checkouts. Provide some detailed commit
messages explaining the issues along the way.

NOTE: I found a couple minor issues with other commands in sparse checkouts
while debugging this issue, but I don't yet have fixes for them and I can
submit them separately.

Elijah Newren (3):
  t7012: add a testcase demonstrating stash apply bugs in sparse
    checkouts
  stash: remove unnecessary process forking
  stash: fix stash application in sparse-checkouts

 builtin/stash.c                  | 130 +++++++++++++++++++++----------
 t/lib-submodule-update.sh        |  16 ++--
 t/t7012-skip-worktree-writing.sh |  88 +++++++++++++++++++++
 3 files changed, 184 insertions(+), 50 deletions(-)

base-commit: faefdd61ec7c7f6f3c8c9907891465ac9a2a1475

Submitted-As: https://lore.kernel.org/git/pull.919.git.git.1605891222.gitgitgadget@gmail.com