Add cache busting to attribute cache

This makes the git attributes and git ignores cache check
stat information before using the file contents from the
cache.  For cached files from the index, it checks the SHA
of the file instead.  This should reduce the need to ever
call `git_attr_cache_flush()` in most situations.

This commit also fixes the `git_status_should_ignore` API
to use the libgit2 standard parameter ordering.

1 files changed, 88 insertions, 30 deletions

diff --git a/src/attr.c b/src/attr.c
index 616cec6ff..1aa965de3 100644
--- a/src/attr.c
+++ b/src/attr.c
@@ -235,31 +235,91 @@ bool git_attr_cache__is_cached(
 	return rval;
 }
 
-static int load_attr_file(const char *filename, const char **data)
+static int load_attr_file(
+	const char **data,
+	git_attr_file_stat_sig *sig,
+	const char *filename)
 {
 	int error;
 	git_buf content = GIT_BUF_INIT;
+	struct stat st;
 
-	error = git_futils_readbuffer(&content, filename);
-	*data = error ? NULL : git_buf_detach(&content);
+	if (p_stat(filename, &st) < 0)
+		return GIT_ENOTFOUND;
 
-	return error;
+	if (sig != NULL &&
+		(git_time_t)st.st_mtime == sig->seconds &&
+		(git_off_t)st.st_size == sig->size &&
+		(unsigned int)st.st_ino == sig->ino)
+		return GIT_ENOTFOUND;
+
+	error = git_futils_readbuffer_updated(&content, filename, NULL, NULL);
+	if (error < 0)
+		return error;
+
+	if (sig != NULL) {
+		sig->seconds = (git_time_t)st.st_mtime;
+		sig->size    = (git_off_t)st.st_size;
+		sig->ino     = (unsigned int)st.st_ino;
+	}
+
+	*data = git_buf_detach(&content);
+
+	return 0;
 }
 
 static int load_attr_blob_from_index(
-	git_repository *repo, const char *filename, git_blob **blob)
+	const char **content,
+	git_blob **blob,
+	git_repository *repo,
+	const git_oid *old_oid,
+	const char *relfile)
 {
 	int error;
 	git_index *index;
 	git_index_entry *entry;
 
 	if ((error = git_repository_index__weakptr(&index, repo)) < 0 ||
-		(error = git_index_find(index, filename)) < 0)
+		(error = git_index_find(index, relfile)) < 0)
 		return error;
 
 	entry = git_index_get(index, error);
 
-	return git_blob_lookup(blob, repo, &entry->oid);
+	if (old_oid && git_oid_cmp(old_oid, &entry->oid) == 0)
+		return GIT_ENOTFOUND;
+
+	if ((error = git_blob_lookup(blob, repo, &entry->oid)) < 0)
+		return error;
+
+	*content = git_blob_rawcontent(*blob);
+	return 0;
+}
+
+static int load_attr_from_cache(
+	git_attr_file **file,
+	git_attr_cache *cache,
+	git_attr_file_source source,
+	const char *relative_path)
+{
+	git_buf  cache_key = GIT_BUF_INIT;
+	khiter_t cache_pos;
+
+	*file = NULL;
+
+	if (!cache || !cache->files)
+		return 0;
+
+	if (git_buf_printf(&cache_key, "%d#%s", (int)source, relative_path) < 0)
+		return -1;
+
+	cache_pos = git_strmap_lookup_index(cache->files, cache_key.ptr);
+
+	git_buf_free(&cache_key);
+
+	if (git_strmap_valid_index(cache->files, cache_pos))
+		*file = git_strmap_value_at(cache->files, cache_pos);
+
+	return 0;
 }
 
 int git_attr_cache__internal_file(
@@ -301,6 +361,7 @@ int git_attr_cache__push_file(
 	git_attr_cache *cache = git_repository_attr_cache(repo);
 	git_attr_file *file = NULL;
 	git_blob *blob = NULL;
+	git_attr_file_stat_sig st;
 
 	assert(filename && stack);
 
@@ -316,30 +377,23 @@ int git_attr_cache__push_file(
 		relfile += strlen(workdir);
 
 	/* check cache */
-	if (cache && cache->files) {
-		git_buf  cache_key = GIT_BUF_INIT;
-		khiter_t cache_pos;
-
-		if (git_buf_printf(&cache_key, "%d#%s", (int)source, relfile) < 0)
-			return -1;
+	if (load_attr_from_cache(&file, cache, source, relfile) < 0)
+		return -1;
 
-		cache_pos = git_strmap_lookup_index(cache->files, cache_key.ptr);
+	/* if not in cache, load data, parse, and cache */
 
-		git_buf_free(&cache_key);
+	if (source == GIT_ATTR_FILE_FROM_FILE) {
+		if (file)
+			memcpy(&st, &file->cache_data.st, sizeof(st));
+		else
+			memset(&st, 0, sizeof(st));
 
-		if (git_strmap_valid_index(cache->files, cache_pos)) {
-			file = git_strmap_value_at(cache->files, cache_pos);
-			goto finish;
-		}
+		error = load_attr_file(&content, &st, filename);
+	} else {
+		error = load_attr_blob_from_index(&content, &blob,
+			repo, file ? &file->cache_data.oid : NULL, relfile);
 	}
 
-	/* if not in cache, load data, parse, and cache */
-
-	if (source == GIT_ATTR_FILE_FROM_FILE)
-		error = load_attr_file(filename, &content);
-	else
-		error = load_attr_blob_from_index(repo, relfile, &blob);
-
 	if (error) {
 		/* not finding a file is not an error for this function */
 		if (error == GIT_ENOTFOUND) {
@@ -349,10 +403,8 @@ int git_attr_cache__push_file(
 		goto finish;
 	}
 
-	if (blob)
-		content = git_blob_rawcontent(blob);
-
-	if ((error = git_attr_file__new(&file, source, relfile, &cache->pool)) < 0)
+	if (!file &&
+		(error = git_attr_file__new(&file, source, relfile, &cache->pool)) < 0)
 		goto finish;
 
 	if (parse && (error = parse(repo, content, file)) < 0)
@@ -362,6 +414,12 @@ int git_attr_cache__push_file(
 	if (error > 0)
 		error = 0;
 
+	/* remember "cache buster" file signature */
+	if (blob)
+		git_oid_cpy(&file->cache_data.oid, git_object_id((git_object *)blob));
+	else
+		memcpy(&file->cache_data.st, &st, sizeof(st));
+
 finish:
 	/* push file onto vector if we found one*/
 	if (!error && file != NULL)