unpack-trees: allow Porcelain to give different error messages

diff --git a/xdiff-interface.c b/xdiff-interface.c
index bba236428adb0b34421b9f1b5a3a1728911ee406..61dc5c547019776b971dc89d009f628bbac134fd 100644 (file)
--- a/xdiff-interface.c
+++ b/xdiff-interface.c
@@ -152,8 +152,8 @@ int read_mmfile(mmfile_t *ptr, const char *filename)
        if ((f = fopen(filename, "rb")) == NULL)
                return error("Could not open %s", filename);
        sz = xsize_t(st.st_size);
-       ptr->ptr = xmalloc(sz);
-       if (fread(ptr->ptr, sz, 1, f) != 1)
+       ptr->ptr = xmalloc(sz ? sz : 1);
+       if (sz && fread(ptr->ptr, sz, 1, f) != 1)
                return error("Could not read %s", filename);
        fclose(f);
        ptr->size = sz;