cache,tree: move basic name compare functions from read-cache to tree

None of base_name_compare(), df_name_compare(), or name_compare()
depended upon a cache_entry or index_state in any way.  By moving these
functions to tree.h, half a dozen other files can stop depending upon
cache.h (though that change will be made in a later commit).

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

tree.c

@@ -94,6 +94,74 @@ int read_tree(struct repository *r,
 	return ret;
 }
 
+int base_name_compare(const char *name1, size_t len1, int mode1,
+		      const char *name2, size_t len2, int mode2)
+{
+	unsigned char c1, c2;
+	size_t len = len1 < len2 ? len1 : len2;
+	int cmp;
+
+	cmp = memcmp(name1, name2, len);
+	if (cmp)
+		return cmp;
+	c1 = name1[len];
+	c2 = name2[len];
+	if (!c1 && S_ISDIR(mode1))
+		c1 = '/';
+	if (!c2 && S_ISDIR(mode2))
+		c2 = '/';
+	return (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
+}
+
+/*
+ * df_name_compare() is identical to base_name_compare(), except it
+ * compares conflicting directory/file entries as equal. Note that
+ * while a directory name compares as equal to a regular file, they
+ * then individually compare _differently_ to a filename that has
+ * a dot after the basename (because '\0' < '.' < '/').
+ *
+ * This is used by routines that want to traverse the git namespace
+ * but then handle conflicting entries together when possible.
+ */
+int df_name_compare(const char *name1, size_t len1, int mode1,
+		    const char *name2, size_t len2, int mode2)
+{
+	unsigned char c1, c2;
+	size_t len = len1 < len2 ? len1 : len2;
+	int cmp;
+
+	cmp = memcmp(name1, name2, len);
+	if (cmp)
+		return cmp;
+	/* Directories and files compare equal (same length, same name) */
+	if (len1 == len2)
+		return 0;
+	c1 = name1[len];
+	if (!c1 && S_ISDIR(mode1))
+		c1 = '/';
+	c2 = name2[len];
+	if (!c2 && S_ISDIR(mode2))
+		c2 = '/';
+	if (c1 == '/' && !c2)
+		return 0;
+	if (c2 == '/' && !c1)
+		return 0;
+	return c1 - c2;
+}
+
+int name_compare(const char *name1, size_t len1, const char *name2, size_t len2)
+{
+	size_t min_len = (len1 < len2) ? len1 : len2;
+	int cmp = memcmp(name1, name2, min_len);
+	if (cmp)
+		return cmp;
+	if (len1 < len2)
+		return -1;
+	if (len1 > len2)
+		return 1;
+	return 0;
+}
+
 struct tree *lookup_tree(struct repository *r, const struct object_id *oid)
 {
 	struct object *obj = lookup_object(r, oid);