index/fileops: Correctly process symbolic links

gitfo_exists() used to error out if the given file was a symbolic link,
due to access() returning an error code. This is not expected behaviour,
as gitfo_exists() should only check whether the file itself exists, not
its link target if it is a symbolic link.

Fix this by calling gitfo_lstat() instead, which is just a wrapper for
lstat().

Also fix the same error in index_init_entry().

src/fileops.c

@@ -172,7 +172,9 @@ int gitfo_isfile(const char *path)
 int gitfo_exists(const char *path)
 {
 	assert(path);
-	return access(path, F_OK);
+
+	struct stat st;
+	return gitfo_lstat(path, &st);
 }
 
 git_off_t gitfo_size(git_file fd)

src/fileops.h

@@ -94,6 +94,7 @@ extern int gitfo_mv_force(const char *from, const char *to);
 
 #define gitfo_stat(p,b) stat(p, b)
 #define gitfo_fstat(f,b) fstat(f, b)
+#define gitfo_lstat(p,b) lstat(p,b)
 
 #define gitfo_unlink(p) unlink(p)
 #define gitfo_rmdir(p) rmdir(p)

src/index.c

@@ -405,7 +405,7 @@ static int index_init_entry(git_index_entry *entry, git_index *index, const char
 	if (gitfo_exists(full_path) < 0)
 		return git__throw(GIT_ENOTFOUND, "Failed to initialize entry. %s does not exist", full_path);
 
-	if (gitfo_stat(full_path, &st) < 0)
+	if (gitfo_lstat(full_path, &st) < 0)
 		return git__throw(GIT_EOSERR, "Failed to initialize entry. %s appears to be corrupted", full_path);
 
 	if (stage < 0 || stage > 3)