From ba359fd5070c189f07990c487dc916908830488a Mon Sep 17 00:00:00 2001 From: Elijah Newren Date: Tue, 1 Dec 2020 22:25:18 +0000 Subject: [PATCH] stash: fix stash application in sparse-checkouts sparse-checkouts are built on the patterns in the $GIT_DIR/info/sparse-checkout file, where commands have modified behavior for paths that do not match those patterns. The differences in behavior, as far as the bugs concerned here, fall into three different categories (with git subcommands that fall into each category listed): * commands that only look at files matching the patterns: * status * diff * clean * update-index * commands that remove files from the working tree that do not match the patterns, and restore files that do match them: * read-tree * switch * checkout * reset (--hard) * commands that omit writing files to the working tree that do not match the patterns, unless those files are not clean: * merge * rebase * cherry-pick * revert There are some caveats above, e.g. a plain `git diff` ignores files outside the sparsity patterns but will show diffs for paths outside the sparsity patterns when revision arguments are passed. (Technically, diff is treating the sparse paths as matching HEAD.) So, there is some internal inconsistency among these commands. There are also additional commands that should behave differently in the face of sparse-checkouts, as the sparse-checkout documentation alludes to, but the above is sufficient for me to explain how `git stash` is affected. What is relevant here is that logically 'stash' should behave like a merge; it three-way merges the changes the user had in progress at stash creation time, the HEAD at the time the stash was created, and the current HEAD, in order to get the stashed changes applied to the current branch. However, this simplistic view doesn't quite work in practice, because stash tweaks it a bit due to two factors: (1) flags like --keep-index and --include-untracked (why we used two different verbs, 'keep' and 'include', is a rant for another day) modify what should be staged at the end and include more things that should be quasi-merged, (2) stash generally wants changes to NOT be staged. It only provides exceptions when (a) some of the changes had conflicts and thus we want to use stages to denote the clean merges and higher order stages to mark the conflicts, or (b) if there is a brand new file we don't want it to become untracked. stash has traditionally gotten this special behavior by first doing a merge, and then when it's clean, applying a pipeline of commands to modify the result. This series of commands for unstaging-non-newly-added-files came from the following commands: git diff-index --cached --name-only --diff-filter=A $CTREE >"$a" git read-tree --reset $CTREE git update-index --add --stdin <"$a" rm -f "$a" Looking back at the different types of special sparsity handling listed at the beginning of this message, you may note that we have at least one of each type covered here: merge, diff-index, and read-tree. The weird mix-and-match led to 3 different bugs: (1) If a path merged cleanly and it didn't match the sparsity patterns, the merge backend would know to avoid writing it to the working tree and keep the SKIP_WORKTREE bit, simply only updating it in the index. Unfortunately, the subsequent commands would essentially undo the changes in the index and thus simply toss the changes altogether since there was nothing left in the working tree. This means the stash is only partially applied. (2) If a path existed in the worktree before `git stash apply` despite having the SKIP_WORKTREE bit set, then the `git read-tree --reset` would print an error message of the form error: Entry 'modified' not uptodate. Cannot merge. and cause stash to abort early. (3) If there was a brand new file added by the stash, then the diff-index command would save that pathname to the temporary file, the read-tree --reset would remove it from the index, and the update-index command would barf due to no such file being present in the working copy; it would print a message of the form: error: NEWFILE: does not exist and --remove not passed fatal: Unable to process path NEWFILE and then cause stash to abort early. Basically, the whole idea of unstage-unless-brand-new requires special care when you are dealing with a sparse-checkout. Fix these problems by applying the following simple rule: When we unstage files, if they have the SKIP_WORKTREE bit set, clear that bit and write the file out to the working directory. (*) If there's already a file present in the way, rename it first. This fixes all three problems in t7012.13 and allows us to mark it as passing. Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano --- builtin/stash.c | 50 ++++++++++++++++++++++++++++++-- t/t7012-skip-worktree-writing.sh | 2 +- 2 files changed, 49 insertions(+), 3 deletions(-) diff --git a/builtin/stash.c b/builtin/stash.c index 3c641cc5cd..9839835dae 100644 --- a/builtin/stash.c +++ b/builtin/stash.c @@ -363,12 +363,23 @@ static void unstage_changes_unless_new(struct object_id *orig_tree) * relevant trees, and the merge logic always stages whatever merges * cleanly. We want to unstage those changes, unless it corresponds * to a file that didn't exist as of orig_tree. + * + * However, if any SKIP_WORKTREE path is modified relative to + * orig_tree, then we want to clear the SKIP_WORKTREE bit and write + * it to the worktree before unstaging. */ + struct checkout state = CHECKOUT_INIT; struct diff_options diff_opts; struct lock_file lock = LOCK_INIT; int i; + /* If any entries have skip_worktree set, we'll have to check 'em out */ + state.force = 1; + state.quiet = 1; + state.refresh_cache = 1; + state.istate = &the_index; + /* * Step 1: get a difference between orig_tree (which corresponding * to the index before a merge was run) and the current index @@ -395,7 +406,42 @@ static void unstage_changes_unless_new(struct object_id *orig_tree) strlen(p->two->path)); /* - * Step 2: "unstage" changes, as long as they are still tracked + * Step 2: Place changes in the working tree + * + * Stash is about restoring changes *to the working tree*. + * So if the merge successfully got a new version of some + * path, but left it out of the working tree, then clear the + * SKIP_WORKTREE bit and write it to the working tree. + */ + if (pos >= 0 && ce_skip_worktree(active_cache[pos])) { + struct stat st; + + ce = active_cache[pos]; + if (!lstat(ce->name, &st)) { + /* Conflicting path present; relocate it */ + struct strbuf new_path = STRBUF_INIT; + int fd; + + strbuf_addf(&new_path, + "%s.stash.XXXXXX", ce->name); + fd = xmkstemp(new_path.buf); + close(fd); + printf(_("WARNING: Untracked file in way of " + "tracked file! Renaming\n " + " %s -> %s\n" + " to make room.\n"), + ce->name, new_path.buf); + if (rename(ce->name, new_path.buf)) + die("Failed to move %s to %s\n", + ce->name, new_path.buf); + strbuf_release(&new_path); + } + checkout_entry(ce, &state, NULL, NULL); + ce->ce_flags &= ~CE_SKIP_WORKTREE; + } + + /* + * Step 3: "unstage" changes, as long as they are still tracked */ if (p->one->oid_valid) { /* @@ -417,7 +463,7 @@ static void unstage_changes_unless_new(struct object_id *orig_tree) diff_flush(&diff_opts); /* - * Step 3: write the new index to disk + * Step 4: write the new index to disk */ repo_hold_locked_index(the_repository, &lock, LOCK_DIE_ON_ERROR); if (write_locked_index(&the_index, &lock, diff --git a/t/t7012-skip-worktree-writing.sh b/t/t7012-skip-worktree-writing.sh index a184ee97fb..e5c6a038fb 100755 --- a/t/t7012-skip-worktree-writing.sh +++ b/t/t7012-skip-worktree-writing.sh @@ -149,7 +149,7 @@ test_expect_success '--ignore-skip-worktree-entries leaves worktree alone' ' --diff-filter=D -- keep-me.t ' -test_expect_failure 'stash restore in sparse checkout' ' +test_expect_success 'stash restore in sparse checkout' ' test_create_repo stash-restore && ( cd stash-restore &&