checkout: only consider nsecs when built that way

When examining the working directory and determining whether it's
up-to-date, only consider the nanoseconds in the index entry when
built with `GIT_USE_NSEC`.  This prevents us from believing that
the working directory is always dirty when the index was originally
written with a git client that uinderstands nsecs (like git 2.x).

src/checkout.c

@@ -200,8 +200,7 @@ static bool checkout_is_workdir_modified(
 	 * out.)
 	 */
 	if ((ie = git_index_get_bypath(data->index, wditem->path, 0)) != NULL) {
-		if (wditem->mtime.seconds == ie->mtime.seconds &&
-			wditem->mtime.nanoseconds == ie->mtime.nanoseconds &&
+		if (git_index_time_eq(&wditem->mtime, &ie->mtime) &&
 			wditem->file_size == ie->file_size)
 			return !is_workdir_base_or_new(&ie->id, baseitem, newitem);
 	}

src/diff.c

@@ -494,11 +494,6 @@ static int diff_list_apply_options(
 
 	/* Don't set GIT_DIFFCAPS_USE_DEV - compile time option in core git */
 
-	/* Don't trust nanoseconds; we do not load nanos from disk */
-#ifdef GIT_USE_NSEC
-	diff->diffcaps = diff->diffcaps | GIT_DIFFCAPS_TRUST_NANOSECS;
-#endif
-
 	/* If not given explicit `opts`, check `diff.xyz` configs */
 	if (!opts) {
 		int context = git_config__get_int_force(cfg, "diff.context", 3);
@@ -699,38 +694,6 @@ int git_diff__oid_for_entry(
 	return error;
 }
 
-static bool diff_time_eq(
-	const git_index_time *a, const git_index_time *b, bool use_nanos)
-{
-	return a->seconds == b->seconds &&
-		(!use_nanos || a->nanoseconds == b->nanoseconds);
-}
-
-/*
- * Test if the given index time is newer than the given existing index entry.
- * If the timestamps are exactly equivalent, then the given index time is
- * considered "racily newer" than the existing index entry.
- */
-static bool diff_newer_than_index(
-	const git_index_time *a, const git_index *b, bool use_nanos)
-{
-	bool is_newer = false;
-
-	if(!b)
-		return false;
-
-	is_newer = is_newer || (a->seconds > (int32_t) b->stamp.mtime.tv_sec);
-	is_newer = is_newer || (!use_nanos &&
-		(a->seconds == (int32_t) b->stamp.mtime.tv_sec));
-	if(use_nanos)
-	{
-		is_newer = is_newer || ((a->seconds == (int32_t) b->stamp.mtime.tv_sec) &&
-			(a->nanoseconds >= (uint32_t) b->stamp.mtime.tv_nsec));
-	}
-
-	return is_newer;
-}
-
 typedef struct {
 	git_repository *repo;
 	git_iterator *old_iter;
@@ -863,11 +826,6 @@ static int maybe_modified(
 	 */
 	} else if (git_oid_iszero(&nitem->id) && new_is_workdir) {
 		bool use_ctime = ((diff->diffcaps & GIT_DIFFCAPS_TRUST_CTIME) != 0);
-#ifdef GIT_USE_NSEC
-		bool use_nanos = ((diff->diffcaps & GIT_DIFFCAPS_TRUST_NANOSECS) != 0);
-#else
-		bool use_nanos = false;
-#endif
 		git_index *index;
 		git_iterator_index(&index, info->new_iter);
 
@@ -886,13 +844,12 @@ static int maybe_modified(
 			modified_uncertain =
 				(oitem->file_size <= 0 && nitem->file_size > 0);
 		}
-		else if (!diff_time_eq(&oitem->mtime, &nitem->mtime, use_nanos) ||
-			(use_ctime &&
-			 !diff_time_eq(&oitem->ctime, &nitem->ctime, use_nanos)) ||
+		else if (!git_index_time_eq(&oitem->mtime, &nitem->mtime) ||
+			(use_ctime && !git_index_time_eq(&oitem->ctime, &nitem->ctime)) ||
 			oitem->ino != nitem->ino ||
 			oitem->uid != nitem->uid ||
 			oitem->gid != nitem->gid ||
-			diff_newer_than_index(&nitem->mtime, index, use_nanos))
+			git_index_entry_newer_than_index(nitem, index))
 		{
 			status = GIT_DELTA_MODIFIED;
 			modified_uncertain = true;

src/diff.h

@@ -28,7 +28,6 @@ enum {
 	GIT_DIFFCAPS_TRUST_MODE_BITS  = (1 << 2), /* use st_mode? */
 	GIT_DIFFCAPS_TRUST_CTIME      = (1 << 3), /* use st_ctime? */
 	GIT_DIFFCAPS_USE_DEV          = (1 << 4), /* use st_dev? */
-	GIT_DIFFCAPS_TRUST_NANOSECS   = (1 << 5), /* use stat time nanoseconds */
 };
 
 #define DIFF_FLAGS_KNOWN_BINARY (GIT_DIFF_FLAG_BINARY|GIT_DIFF_FLAG_NOT_BINARY)

src/index.c

@@ -720,27 +720,13 @@ int git_index__changed_relative_to(
 	return !!git_oid_cmp(&index->checksum, checksum);
 }
 
-static bool is_racy_timestamp(const struct timespec *stamp, git_index_entry *entry)
+static bool is_racy_entry(git_index *index, const git_index_entry *entry)
 {
 	/* Git special-cases submodules in the check */
 	if (S_ISGITLINK(entry->mode))
 		return false;
 
-	/* If we never read the index, we can't have this race either */
-	if(stamp->tv_sec == 0)
-		return false;
-
-	/* If the timestamp is the same or newer than the index, it's racy */
-#if defined(GIT_USE_NSEC)
-	if((int32_t) stamp->tv_sec < entry->mtime.seconds)
-		return true;
-	else if((int32_t) stamp->tv_sec > entry->mtime.seconds)
-		return false;
-	else
-		return (uint32_t) stamp->tv_nsec <= entry->mtime.nanoseconds;
-#else
-	return ((int32_t) stamp->tv_sec) <= entry->mtime.seconds;
-#endif
+	return git_index_entry_newer_than_index(entry, index);
 }
 
 /*
@@ -768,7 +754,7 @@ static int truncate_racily_clean(git_index *index)
 	diff_opts.flags |= GIT_DIFF_INCLUDE_TYPECHANGE | GIT_DIFF_IGNORE_SUBMODULES | GIT_DIFF_DISABLE_PATHSPEC_MATCH;
 	git_vector_foreach(&index->entries, i, entry) {
 		if ((entry->flags_extended & GIT_IDXENTRY_UPTODATE) == 0 &&
-			is_racy_timestamp(&index->stamp.mtime, entry))
+			is_racy_entry(index, entry))
 			git_vector_insert(&paths, (char *)entry->path);
 	}
 

src/index.h

@@ -65,6 +65,45 @@ extern int git_index_entry_icmp(const void *a, const void *b);
 extern int git_index_entry_srch(const void *a, const void *b);
 extern int git_index_entry_isrch(const void *a, const void *b);
 
+/* Index time handling functions */
+GIT_INLINE(bool) git_index_time_eq(const git_index_time *one, const git_index_time *two)
+{
+	if (one->seconds != two->seconds)
+		return false;
+
+#ifdef GIT_USE_NSEC
+	if (one->nanoseconds != two->nanoseconds)
+		return false;
+#endif
+
+	return true;
+}
+
+/*
+ * Test if the given index time is newer than the given existing index entry.
+ * If the timestamps are exactly equivalent, then the given index time is
+ * considered "racily newer" than the existing index entry.
+ */
+GIT_INLINE(bool) git_index_entry_newer_than_index(
+	const git_index_entry *entry, git_index *index)
+{
+	/* If we never read the index, we can't have this race either */
+	if (!index || index->stamp.mtime.tv_sec == 0)
+		return false;
+
+	/* If the timestamp is the same or newer than the index, it's racy */
+#if defined(GIT_USE_NSEC)
+	if ((int32_t)index->stamp.tv_sec < entry->mtime.seconds)
+		return true;
+	else if ((int32_t)index->stamp.mtime.tv_sec > entry->mtime.seconds)
+		return false;
+	else
+		return (uint32_t)index->stamp.mtime.tv_nsec <= entry->mtime.nanoseconds;
+#else
+	return ((int32_t)index->stamp.mtime.tv_sec) <= entry->mtime.seconds;
+#endif
+}
+
 /* Search index for `path`, returning GIT_ENOTFOUND if it does not exist
  * (but not setting an error message).
  *