Merge branch 'ci/forbid-unwanted-current-branch-update'

* ci/forbid-unwanted-current-branch-update:
  branch --set-upstream: regression fix

branch.c

@@ -135,23 +135,25 @@ static int setup_tracking(const char *new_ref, const char *orig_ref,
 	return 0;
 }
 
-int validate_new_branchname(const char *name, struct strbuf *ref, int force)
+int validate_new_branchname(const char *name, struct strbuf *ref,
+			    int force, int attr_only)
 {
-	const char *head;
-	unsigned char sha1[20];
-
 	if (strbuf_check_branch_ref(ref, name))
 		die("'%s' is not a valid branch name.", name);
 
 	if (!ref_exists(ref->buf))
 		return 0;
-	else if (!force)
+	else if (!force && !attr_only)
 		die("A branch named '%s' already exists.", ref->buf + strlen("refs/heads/"));
 
+	if (!attr_only) {
+		const char *head;
+		unsigned char sha1[20];
+
 		head = resolve_ref("HEAD", sha1, 0, NULL);
 		if (!is_bare_repository() && head && !strcmp(head, ref->buf))
 			die("Cannot force update the current branch.");
-
+	}
 	return 1;
 }
 
@@ -171,7 +173,8 @@ void create_branch(const char *head,
 	if (track == BRANCH_TRACK_EXPLICIT || track == BRANCH_TRACK_OVERRIDE)
 		explicit_tracking = 1;
 
-	if (validate_new_branchname(name, &ref, force || track == BRANCH_TRACK_OVERRIDE)) {
+	if (validate_new_branchname(name, &ref, force,
+				    track == BRANCH_TRACK_OVERRIDE)) {
 		if (!force)
 			dont_change_ref = 1;
 		else

branch.h

@@ -20,8 +20,18 @@ void create_branch(const char *head, const char *name, const char *start_name,
  * interpreted ref in ref, force indicates whether (non-head) branches
  * may be overwritten. A non-zero return value indicates that the force
  * parameter was non-zero and the branch already exists.
+ *
+ * Contrary to all of the above, when attr_only is 1, the caller is
+ * not interested in verifying if it is Ok to update the named
+ * branch to point at a potentially different commit. It is merely
+ * asking if it is OK to change some attribute for the named branch
+ * (e.g. tracking upstream).
+ *
+ * NEEDSWORK: This needs to be split into two separate functions in the
+ * longer run for sanity.
+ *
  */
-int validate_new_branchname(const char *name, struct strbuf *ref, int force);
+int validate_new_branchname(const char *name, struct strbuf *ref, int force, int attr_only);
 
 /*
  * Remove information about the state of working on the current

builtin/branch.c

@@ -566,7 +566,7 @@ static void rename_branch(const char *oldname, const char *newname, int force)
 			die(_("Invalid branch name: '%s'"), oldname);
 	}
 
-	validate_new_branchname(newname, &newref, force);
+	validate_new_branchname(newname, &newref, force, 0);
 
 	strbuf_addf(&logmsg, "Branch: renamed %s to %s",
 		 oldref.buf, newref.buf);

builtin/checkout.c

@@ -1073,7 +1073,8 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	if (opts.new_branch) {
 		struct strbuf buf = STRBUF_INIT;
 
-		opts.branch_exists = validate_new_branchname(opts.new_branch, &buf, !!opts.new_branch_force);
+		opts.branch_exists = validate_new_branchname(opts.new_branch, &buf,
+							     !!opts.new_branch_force, 0);
 
 		strbuf_release(&buf);
 	}

t/t3200-branch.sh

@@ -554,4 +554,17 @@ test_expect_success 'attempt to delete a branch merged to its base' '
 	test_must_fail git branch -d my10
 '
 
+test_expect_success 'use set-upstream on the current branch' '
+	git checkout master &&
+	git --bare init myupstream.git &&
+	git push myupstream.git master:refs/heads/frotz &&
+	git remote add origin myupstream.git &&
+	git fetch &&
+	git branch --set-upstream master origin/frotz &&
+
+	test "z$(git config branch.master.remote)" = "zorigin" &&
+	test "z$(git config branch.master.merge)" = "zrefs/heads/frotz"
+
+'
+
 test_done