[PATCH 20/27] sparse-index: expand_to_path() trivial implementation

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

From: Derrick Stolee <dstolee@microsoft.com>

Before we check if a specific file or directory exists in the index, it
would be good to see if a leading directory is a sparse-directory. If
so, we will want to expand the index _just enough_ to be sure that the
paths we are interested in are in the index.

The actually-interesting implementation will follow in a later change.
For now, simply call ensure_full_index() to expand every directory
simultaneously.

Calls like index_dir_exists(), adjust_dirname_case(), and
index_file_exists() in name-hash.c can trust the name hash if the index
was properly expanded for the requested names. These methods can
transition from ensure_full_index() to expand_to_path().

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 name-hash.c    | 10 ++++------
 sparse-index.c |  7 +++++++
 sparse-index.h | 12 ++++++++++++
 3 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/name-hash.c b/name-hash.c
index 0f6d4fcca5a..641f6900a7c 100644
--- a/name-hash.c
+++ b/name-hash.c
@@ -8,6 +8,7 @@
 #include "cache.h"
 #include "thread-utils.h"
 #include "trace2.h"
+#include "sparse-index.h"
 
 struct dir_entry {
 	struct hashmap_entry ent;
@@ -679,9 +680,8 @@ int index_dir_exists(struct index_state *istate, const char *name, int namelen)
 {
 	struct dir_entry *dir;
 
-	ensure_full_index(istate);
-
 	lazy_init_name_hash(istate);
+	expand_to_path(istate, name, namelen, 0);
 	dir = find_dir_entry(istate, name, namelen);
 	return dir && dir->nr;
 }
@@ -691,9 +691,8 @@ void adjust_dirname_case(struct index_state *istate, char *name)
 	const char *startPtr = name;
 	const char *ptr = startPtr;
 
-	ensure_full_index( istate);
-
 	lazy_init_name_hash(istate);
+	expand_to_path(istate, name, strlen(name), 0);
 	while (*ptr) {
 		while (*ptr && *ptr != '/')
 			ptr++;
@@ -716,9 +715,8 @@ struct cache_entry *index_file_exists(struct index_state *istate, const char *na
 	struct cache_entry *ce;
 	unsigned int hash = memihash(name, namelen);
 
-	ensure_full_index(istate);
-
 	lazy_init_name_hash(istate);
+	expand_to_path(istate, name, namelen, icase);
 
 	ce = hashmap_get_entry_from_hash(&istate->name_hash, hash, NULL,
 					 struct cache_entry, ent);
diff --git a/sparse-index.c b/sparse-index.c
index 3552f88fb03..dd1a06dfdd3 100644
--- a/sparse-index.c
+++ b/sparse-index.c
@@ -280,3 +280,10 @@ void ensure_full_index(struct index_state *istate)
 
 	trace2_region_leave("index", "ensure_full_index", istate->repo);
 }
+
+void expand_to_path(struct index_state *istate,
+		    const char *path, size_t pathlen, int icase)
+{
+	/* for now, do the obviously-correct, slow thing */
+	ensure_full_index(istate);
+}
diff --git a/sparse-index.h b/sparse-index.h
index ca936e95d11..549e4171f1a 100644
--- a/sparse-index.h
+++ b/sparse-index.h
@@ -4,6 +4,18 @@
 struct index_state;
 void ensure_full_index(struct index_state *istate);
 int convert_to_sparse(struct index_state *istate);
+/*
+ * Some places in the codebase expect to search for a specific path.
+ * This path might be outside of the sparse-checkout definition, in
+ * which case a sparse-index may not contain a path for that index.
+ *
+ * Given an index and a path, check to see if a leading directory for
+ * 'path' exists in the index as a sparse directory. In that case,
+ * expand that sparse directory to a full range of cache entries and
+ * populate the index accordingly.
+ */
+void expand_to_path(struct index_state *istate,
+		    const char *path, size_t pathlen, int icase);
 
 struct repository;
 int set_sparse_index_config(struct repository *repo, int enable);
-- 
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