[PATCH 16/27] unpack-trees: make sparse aware

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <dstolee@microsoft.com>

As a first step to integrate 'git status' and 'git add' with the sparse
index, we must start integrating unpack_trees() with sparse directory
entries. These changes are currently impossible to trigger because
unpack_trees() calls ensure_full_index() if command_requires_full_index
is true. This is the case for all commands at the moment. As we expand
more commands to be sparse-aware, we might find that more changes are
required to unpack_trees(). The current changes will suffice for
'status' and 'add'.

unpack_trees() calls the traverse_trees() API using unpack_callback()
to decide if we should recurse into a subtree. We must add new abilities
to skip a subtree if it corresponds to a sparse directory entry.

It is important to be careful about the trailing directory separator
that exists in the sparse directory entries but not in the subtree
paths.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 dir.h           |  2 +-
 preload-index.c |  2 ++
 read-cache.c    |  3 +++
 unpack-trees.c  | 24 ++++++++++++++++++++++--
 4 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/dir.h b/dir.h
index facfae47402..300305ec335 100644
--- a/dir.h
+++ b/dir.h
@@ -503,7 +503,7 @@ static inline int ce_path_match(const struct index_state *istate,
 				char *seen)
 {
 	return match_pathspec(istate, pathspec, ce->name, ce_namelen(ce), 0, seen,
-			      S_ISDIR(ce->ce_mode) || S_ISGITLINK(ce->ce_mode));
+			      S_ISSPARSEDIR(ce) || S_ISDIR(ce->ce_mode) || S_ISGITLINK(ce->ce_mode));
 }
 
 static inline int dir_path_match(const struct index_state *istate,
diff --git a/preload-index.c b/preload-index.c
index ed6eaa47388..323fc8c5100 100644
--- a/preload-index.c
+++ b/preload-index.c
@@ -54,6 +54,8 @@ static void *preload_thread(void *_data)
 			continue;
 		if (S_ISGITLINK(ce->ce_mode))
 			continue;
+		if (S_ISSPARSEDIR(ce))
+			continue;
 		if (ce_uptodate(ce))
 			continue;
 		if (ce_skip_worktree(ce))
diff --git a/read-cache.c b/read-cache.c
index 65679d70d7c..ab0c2b86ec0 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1572,6 +1572,9 @@ int refresh_index(struct index_state *istate, unsigned int flags,
 		if (ignore_submodules && S_ISGITLINK(ce->ce_mode))
 			continue;
 
+		if (istate->sparse_index && S_ISSPARSEDIR(ce))
+			continue;
+
 		if (pathspec && !ce_path_match(istate, ce, pathspec, seen))
 			filtered = 1;
 
diff --git a/unpack-trees.c b/unpack-trees.c
index b324eec2a5d..90644856a80 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -583,6 +583,13 @@ static void mark_ce_used(struct cache_entry *ce, struct unpack_trees_options *o)
 {
 	ce->ce_flags |= CE_UNPACKED;
 
+	/*
+	 * If this is a sparse directory, don't advance cache_bottom.
+	 * That will be advanced later using the cache-tree data.
+	 */
+	if (S_ISSPARSEDIR(ce))
+		return;
+
 	if (o->cache_bottom < o->src_index->cache_nr &&
 	    o->src_index->cache[o->cache_bottom] == ce) {
 		int bottom = o->cache_bottom;
@@ -980,6 +987,9 @@ static int do_compare_entry(const struct cache_entry *ce,
 	ce_len -= pathlen;
 	ce_name = ce->name + pathlen;
 
+	/* remove directory separator if a sparse directory entry */
+	if (S_ISSPARSEDIR(ce))
+		ce_len--;
 	return df_name_compare(ce_name, ce_len, S_IFREG, name, namelen, mode);
 }
 
@@ -989,6 +999,10 @@ static int compare_entry(const struct cache_entry *ce, const struct traverse_inf
 	if (cmp)
 		return cmp;
 
+	/* If ce is a sparse directory, then allow equality here. */
+	if (S_ISSPARSEDIR(ce))
+		return 0;
+
 	/*
 	 * Even if the beginning compared identically, the ce should
 	 * compare as bigger than a directory leading up to it!
@@ -1239,6 +1253,7 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
 	struct cache_entry *src[MAX_UNPACK_TREES + 1] = { NULL, };
 	struct unpack_trees_options *o = info->data;
 	const struct name_entry *p = names;
+	unsigned recurse = 1;
 
 	/* Find first entry with a real name (we could use "mask" too) */
 	while (!p->mode)
@@ -1280,12 +1295,16 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
 					}
 				}
 				src[0] = ce;
+
+				if (S_ISSPARSEDIR(ce))
+					recurse = 0;
 			}
 			break;
 		}
 	}
 
-	if (unpack_nondirectories(n, mask, dirmask, src, names, info) < 0)
+	if (recurse &&
+	    unpack_nondirectories(n, mask, dirmask, src, names, info) < 0)
 		return -1;
 
 	if (o->merge && src[0]) {
@@ -1315,7 +1334,8 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
 			}
 		}
 
-		if (traverse_trees_recursive(n, dirmask, mask & ~dirmask,
+		if (recurse &&
+		    traverse_trees_recursive(n, dirmask, mask & ~dirmask,
 					     names, info) < 0)
 			return -1;
 		return mask;
-- 
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