Avoid some unnecessary lstat() calls

The commit sequence used to do

	if (file_exists(p->path))
		add_file_to_cache(p->path, 0);

where both "file_exists()" and "add_file_to_cache()" needed to do a
lstat() on the path to do their work.

This cuts down 'lstat()' calls for the partial commit case by two
for each path we know about (because we do this twice per path).

Just move the lstat() to the caller instead (that's all that
"file_exists()" really does), and pass the stat information down to the
add_to_cache() function.

This essentially makes 'add_to_index()' the core function that adds a path
to the index, getting the index pointer, the pathname and the stat
information as arguments. There are then shorthand helper functions that
use this core function:

 - 'add_to_cache()' is just 'add_to_index()' with the default index

 - 'add_file_to_cache/index()' is the same, but does the lstat() call
   itself, so you can pass just the pathname if you don't already have the
   stat information available.

So old users of the 'add_file_to_xyzzy()' are essentially left unchanged,
and this just exposes the more generic helper function that can take
existing stat information into account.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-commit.c

@@ -175,9 +175,11 @@ static void add_remove_files(struct path_list *list)
 {
 	int i;
 	for (i = 0; i < list->nr; i++) {
+		struct stat st;
 		struct path_list_item *p = &(list->items[i]);
-		if (file_exists(p->path))
-			add_file_to_cache(p->path, 0);
+
+		if (!lstat(p->path, &st))
+			add_to_cache(p->path, &st, 0);
 		else
 			remove_file_from_cache(p->path);
 	}

cache.h

@@ -261,6 +261,7 @@ static inline void remove_name_hash(struct cache_entry *ce)
 #define add_cache_entry(ce, option) add_index_entry(&the_index, (ce), (option))
 #define remove_cache_entry_at(pos) remove_index_entry_at(&the_index, (pos))
 #define remove_file_from_cache(path) remove_file_from_index(&the_index, (path))
+#define add_to_cache(path, st, verbose) add_to_index(&the_index, (path), (st), (verbose))
 #define add_file_to_cache(path, verbose) add_file_to_index(&the_index, (path), (verbose))
 #define refresh_cache(flags) refresh_index(&the_index, (flags), NULL, NULL)
 #define ce_match_stat(ce, st, options) ie_match_stat(&the_index, (ce), (st), (options))
@@ -365,6 +366,7 @@ extern int add_index_entry(struct index_state *, struct cache_entry *ce, int opt
 extern struct cache_entry *refresh_cache_entry(struct cache_entry *ce, int really);
 extern int remove_index_entry_at(struct index_state *, int pos);
 extern int remove_file_from_index(struct index_state *, const char *path);
+extern int add_to_index(struct index_state *, const char *path, struct stat *, int verbose);
 extern int add_file_to_index(struct index_state *, const char *path, int verbose);
 extern struct cache_entry *make_cache_entry(unsigned int mode, const unsigned char *sha1, const char *path, int stage, int refresh);
 extern int ce_same_name(struct cache_entry *a, struct cache_entry *b);

read-cache.c

@@ -462,32 +462,29 @@ static struct cache_entry *create_alias_ce(struct cache_entry *ce, struct cache_
 	return new;
 }
 
-int add_file_to_index(struct index_state *istate, const char *path, int verbose)
+int add_to_index(struct index_state *istate, const char *path, struct stat *st, int verbose)
 {
 	int size, namelen;
-	struct stat st;
+	mode_t st_mode = st->st_mode;
 	struct cache_entry *ce, *alias;
 	unsigned ce_option = CE_MATCH_IGNORE_VALID|CE_MATCH_RACY_IS_DIRTY;
 
-	if (lstat(path, &st))
-		die("%s: unable to stat (%s)", path, strerror(errno));
-
-	if (!S_ISREG(st.st_mode) && !S_ISLNK(st.st_mode) && !S_ISDIR(st.st_mode))
+	if (!S_ISREG(st_mode) && !S_ISLNK(st_mode) && !S_ISDIR(st_mode))
 		die("%s: can only add regular files, symbolic links or git-directories", path);
 
 	namelen = strlen(path);
-	if (S_ISDIR(st.st_mode)) {
+	if (S_ISDIR(st_mode)) {
 		while (namelen && path[namelen-1] == '/')
 			namelen--;
 	}
 	size = cache_entry_size(namelen);
 	ce = xcalloc(1, size);
 	memcpy(ce->name, path, namelen);
 	ce->ce_flags = namelen;
-	fill_stat_cache_info(ce, &st);
+	fill_stat_cache_info(ce, st);
 
 	if (trust_executable_bit && has_symlinks)
-		ce->ce_mode = create_ce_mode(st.st_mode);
+		ce->ce_mode = create_ce_mode(st_mode);
 	else {
 		/* If there is an existing entry, pick the mode bits and type
 		 * from it, otherwise assume unexecutable regular file.
@@ -496,18 +493,18 @@ int add_file_to_index(struct index_state *istate, const char *path, int verbose)
 		int pos = index_name_pos_also_unmerged(istate, path, namelen);
 
 		ent = (0 <= pos) ? istate->cache[pos] : NULL;
-		ce->ce_mode = ce_mode_from_stat(ent, st.st_mode);
+		ce->ce_mode = ce_mode_from_stat(ent, st_mode);
 	}
 
 	alias = index_name_exists(istate, ce->name, ce_namelen(ce), ignore_case);
-	if (alias && !ce_stage(alias) && !ie_match_stat(istate, alias, &st, ce_option)) {
+	if (alias && !ce_stage(alias) && !ie_match_stat(istate, alias, st, ce_option)) {
 		/* Nothing changed, really */
 		free(ce);
 		ce_mark_uptodate(alias);
 		alias->ce_flags |= CE_ADDED;
 		return 0;
 	}
-	if (index_path(ce->sha1, path, &st, 1))
+	if (index_path(ce->sha1, path, st, 1))
 		die("unable to index file %s", path);
 	if (ignore_case && alias && different_name(ce, alias))
 		ce = create_alias_ce(ce, alias);
@@ -519,6 +516,14 @@ int add_file_to_index(struct index_state *istate, const char *path, int verbose)
 	return 0;
 }
 
+int add_file_to_index(struct index_state *istate, const char *path, int verbose)
+{
+	struct stat st;
+	if (lstat(path, &st))
+		die("%s: unable to stat (%s)", path, strerror(errno));
+	return add_to_index(istate, path, &st, verbose);
+}
+
 struct cache_entry *make_cache_entry(unsigned int mode,
 		const unsigned char *sha1, const char *path, int stage,
 		int refresh)