[RFC PATCH 4/5] branch: introduce dont_fail parameter for update validation

@@ -178,28 +178,40 @@ int read_branch_desc(struct strbuf *buf, const char *branch_name)
 	return 0;
 }
 
-int validate_branch_update(const char *name, struct strbuf *ref,
-			   int could_exist, int clobber_head)
+int validate_branch_update(const char *name, struct strbuf *ref, int could_exist,
+			   int clobber_head, unsigned dont_fail)
 {
-	if (strbuf_check_branch_ref(ref, name))
-		die(_("'%s' is not a valid branch name."), name);
+	if (strbuf_check_branch_ref(ref, name)) {
+		if (dont_fail)
+			return INVALID_BRANCH_NAME;
+		else
+			die(_("'%s' is not a valid branch name."), name);
+	}
 
 	if (!ref_exists(ref->buf))
-		return 0;
+		return VALID_BRANCH_NAME;
 
-	if (!could_exist)
-		die(_("A branch named '%s' already exists."), ref->buf + strlen("refs/heads/"));
+	if (!could_exist) {
+		if (dont_fail)
+			return BRANCH_EXISTS;
+		else
+			die(_("A branch named '%s' already exists."), ref->buf + strlen("refs/heads/"));
+	}
 
 	if (!clobber_head) {
 		const char *head;
 		struct object_id oid;
 
 		head = resolve_ref_unsafe("HEAD", 0, oid.hash, NULL);
-		if (!is_bare_repository() && head && !strcmp(head, ref->buf))
-			die(_("Cannot force update the current branch."));
+		if (!is_bare_repository() && head && !strcmp(head, ref->buf)) {
+			if (dont_fail)
+				return CANNOT_FORCE_UPDATE_CURRENT_BRANCH;
+			else
+				die(_("Cannot force update the current branch."));
+		}
 	}
 
-	return 1;
+	return FORCE_UPDATING_BRANCH;
 }
 
 /*

@@ -268,7 +280,7 @@ void create_branch(const char *name, const char *start_name,
 		validate_existing_branch(name, &ref);
 		dont_change_ref = 1;
 	} else {
-		forcing = validate_branch_update(name, &ref, force, clobber_head);
+		forcing = validate_branch_update(name, &ref, force, clobber_head, 0);
 	}
 
 	real_ref = NULL;

@@ -27,6 +27,16 @@ void create_branch(const char *name, const char *start_name,
 		   int force, int reflog,
 		   int clobber_head, int quiet, enum branch_track track);
 
+enum branch_validation_result {
+	/* Flags that say it's NOT OK to update */
+	BRANCH_EXISTS = -3,
+	CANNOT_FORCE_UPDATE_CURRENT_BRANCH,
+	INVALID_BRANCH_NAME,
+	/* Flags that say it's OK to update */
+	VALID_BRANCH_NAME = 0,
+	FORCE_UPDATING_BRANCH = 1
+};
+
 /*
  * Validates whether the branch with the given name may be updated (created, renamed etc.,)
  * with respect to the given conditions. It returns the interpreted ref in ref.

@@ -36,10 +46,19 @@ void create_branch(const char *name, const char *start_name,
  * if 'could_exist' is true, clobber_head indicates whether the branch could be the
  * current branch else it has no effect.
  *
- * A non-zero return value indicates that a branch already exists and can be force updated.
+ * The return values have the following meaning,
+ *
+ *   - If dont_fail is 0, the function dies in case of failure and returns flags of
+ *     'validate_result' that specify it is OK to update the branch. The positive
+ *     non-zero flag implies that the branch can be force updated.
+ *
+ *   - If dont_fail is 1, the function doesn't die in case of failure but returns flags
+ *     of 'validate_result' that specify the reason for failure. The behaviour in case of
+ *     success is same as above.
  *
  */
-int validate_branch_update(const char *name, struct strbuf *ref, int could_exist, int clobber_head);
+int validate_branch_update(const char *name, struct strbuf *ref, int could_exist,
+			   int clobber_head, unsigned dont_fail);
 
 /*
  * Remove information about the state of working on the current

@@ -483,7 +483,7 @@ static void rename_branch(const char *oldname, const char *newname, int force)
 	 */
 	clobber_head_ok = !strcmp(oldname, newname);
 
-	validate_branch_update(newname, &newref, force, clobber_head_ok);
+	validate_branch_update(newname, &newref, force, clobber_head_ok, 0);
 
 	reject_rebase_or_bisect_branch(oldref.buf);
 

@@ -1284,7 +1284,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		int force = opts.new_branch_force != NULL;
 
 		opts.branch_exists = validate_branch_update(opts.new_branch, &buf,
-							    force, force);
+							    force, force, 0);
 
 		strbuf_release(&buf);
 	}