[PATCH 21/27] sparse-index: expand_to_path no-op if path exists

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

From: Derrick Stolee <dstolee@microsoft.com>

We need to check the file hashmap first, then look to see if the
directory signals a non-sparse directory entry. In such a case, we can
rely on the contents of the sparse-index.

We still use ensure_full_index() in the case that we hit a path that is
within a sparse-directory entry.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 name-hash.c    |  6 ++++++
 sparse-index.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+)

diff --git a/name-hash.c b/name-hash.c
index 641f6900a7c..cb0f316f652 100644
--- a/name-hash.c
+++ b/name-hash.c
@@ -110,6 +110,12 @@ static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
 	if (ce->ce_flags & CE_HASHED)
 		return;
 	ce->ce_flags |= CE_HASHED;
+
+	if (ce->ce_mode == CE_MODE_SPARSE_DIRECTORY) {
+		add_dir_entry(istate, ce);
+		return;
+	}
+
 	hashmap_entry_init(&ce->ent, memihash(ce->name, ce_namelen(ce)));
 	hashmap_add(&istate->name_hash, &ce->ent);
 
diff --git a/sparse-index.c b/sparse-index.c
index dd1a06dfdd3..bf8dce9a09b 100644
--- a/sparse-index.c
+++ b/sparse-index.c
@@ -281,9 +281,62 @@ void ensure_full_index(struct index_state *istate)
 	trace2_region_leave("index", "ensure_full_index", istate->repo);
 }
 
+static int in_expand_to_path = 0;
+
 void expand_to_path(struct index_state *istate,
 		    const char *path, size_t pathlen, int icase)
 {
+	struct strbuf path_as_dir = STRBUF_INIT;
+	int pos;
+
+	/* prevent extra recursion */
+	if (in_expand_to_path)
+		return;
+
+	if (!istate || !istate->sparse_index)
+		return;
+
+	if (!istate->repo)
+		istate->repo = the_repository;
+
+	in_expand_to_path = 1;
+
+	/*
+	 * We only need to actually expand a region if the
+	 * following are both true:
+	 *
+	 * 1. 'path' is not already in the index.
+	 * 2. Some parent directory of 'path' is a sparse directory.
+	 */
+
+	strbuf_add(&path_as_dir, path, pathlen);
+	strbuf_addch(&path_as_dir, '/');
+
+	/* in_expand_to_path prevents infinite recursion here */
+	if (index_file_exists(istate, path, pathlen, icase))
+		goto cleanup;
+
+	pos = index_name_pos(istate, path_as_dir.buf, path_as_dir.len);
+
+	if (pos < 0)
+		pos = -pos - 1;
+
+	/*
+	 * Even if the path doesn't exist, if the value isn't exactly a
+	 * sparse-directory entry, then there is no need to expand the
+	 * index.
+	 */
+	if (istate->cache[pos]->ce_mode != CE_MODE_SPARSE_DIRECTORY)
+		goto cleanup;
+
+	trace2_region_enter("index", "expand_to_path", istate->repo);
+
 	/* for now, do the obviously-correct, slow thing */
 	ensure_full_index(istate);
+
+	trace2_region_leave("index", "expand_to_path", istate->repo);
+
+cleanup:
+	strbuf_release(&path_as_dir);
+	in_expand_to_path = 0;
 }
-- 
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