extern char *sha1_to_hex(const unsigned char *sha1); /* static buffer result! */
extern char *oid_to_hex(const struct object_id *oid); /* same static buffer as sha1_to_hex */
-extern int interpret_branch_name(const char *str, int len, struct strbuf *);
+/*
+ * This reads short-hand syntax that not only evaluates to a commit
+ * object name, but also can act as if the end user spelled the name
+ * of the branch from the command line.
+ *
+ * - "@{-N}" finds the name of the Nth previous branch we were on, and
+ * places the name of the branch in the given buf and returns the
+ * number of characters parsed if successful.
+ *
+ * - "<branch>@{upstream}" finds the name of the other ref that
+ * <branch> is configured to merge with (missing <branch> defaults
+ * to the current branch), and places the name of the branch in the
+ * given buf and returns the number of characters parsed if
+ * successful.
+ *
+ * If the input is not of the accepted format, it returns a negative
+ * number to signal an error.
+ *
+ * If the input was ok but there are not N branch switches in the
+ * reflog, it returns 0.
+ *
+ * If "allowed" is non-zero, it is a treated as a bitfield of allowable
+ * expansions: local branches ("refs/heads/"), remote branches
+ * ("refs/remotes/"), or "HEAD". If no "allowed" bits are set, any expansion is
+ * allowed, even ones to refs outside of those namespaces.
+ */
+#define INTERPRET_BRANCH_LOCAL (1<<0)
+#define INTERPRET_BRANCH_REMOTE (1<<1)
+#define INTERPRET_BRANCH_HEAD (1<<2)
+extern int interpret_branch_name(const char *str, int len, struct strbuf *,
+ unsigned allowed);
extern int get_oid_mb(const char *str, struct object_id *oid);
extern int validate_headref(const char *ref);