[PATCH 4/5] files_ref_store::submodule: use NULL for the main repository

[Michael Haggerty]

The old practice of storing the empty string in this member for the main
repository was a holdover from before 00eebe3 (refs: create a base class
"ref_store" for files_ref_store, 2016-09-04), when the submodule was
stored in a flex array at the end of `struct files_ref_store`. Storing
NULL for this case is more idiomatic and a tiny bit less code.

Signed-off-by: Michael Haggerty <mhag...@alum.mit.edu>
---
 refs/files-backend.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/refs/files-backend.c b/refs/files-backend.c
index 794b88c..069a8ee 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -915,8 +915,8 @@ struct files_ref_store {
 
        /*
         * The name of the submodule represented by this object, or
-        * the empty string if it represents the main repository's
-        * reference store:
+        * NULL if it represents the main repository's reference
+        * store:
         */
        const char *submodule;
 
@@ -982,7 +982,7 @@ static struct ref_store *files_ref_store_create(const char 
*submodule)
 
        base_ref_store_init(ref_store, &refs_be_files);
 
-       refs->submodule = submodule ? xstrdup(submodule) : "";
+       refs->submodule = xstrdup_or_null(submodule);
 
        return ref_store;
 }
@@ -994,7 +994,7 @@ static struct ref_store *files_ref_store_create(const char 
*submodule)
 static void files_assert_main_repository(struct files_ref_store *refs,
                                         const char *caller)
 {
-       if (*refs->submodule)
+       if (refs->submodule)
                die("BUG: %s called for a submodule", caller);
 }
 
@@ -1158,7 +1158,7 @@ static struct packed_ref_cache 
*get_packed_ref_cache(struct files_ref_store *ref
 {
        char *packed_refs_file;
 
-       if (*refs->submodule)
+       if (refs->submodule)
                packed_refs_file = git_pathdup_submodule(refs->submodule,
                                                         "packed-refs");
        else
@@ -1228,7 +1228,7 @@ static void read_loose_refs(const char *dirname, struct 
ref_dir *dir)
        size_t path_baselen;
        int err = 0;
 
-       if (*refs->submodule)
+       if (refs->submodule)
                err = strbuf_git_path_submodule(&path, refs->submodule, "%s", 
dirname);
        else
                strbuf_git_path(&path, "%s", dirname);
@@ -1269,7 +1269,7 @@ static void read_loose_refs(const char *dirname, struct 
ref_dir *dir)
                } else {
                        int read_ok;
 
-                       if (*refs->submodule) {
+                       if (refs->submodule) {
                                hashclr(sha1);
                                flag = 0;
                                read_ok = !resolve_gitlink_ref(refs->submodule,
@@ -1383,7 +1383,7 @@ static int files_read_raw_ref(struct ref_store *ref_store,
        *type = 0;
        strbuf_reset(&sb_path);
 
-       if (*refs->submodule)
+       if (refs->submodule)
                strbuf_git_path_submodule(&sb_path, refs->submodule, "%s", 
refname);
        else
                strbuf_git_path(&sb_path, "%s", refname);
-- 
2.9.3